Enable tsconfig noUncheckedIndexedAccess

app/attachment_channel.main.ts

@@ -791,13 +791,15 @@ function handleRangeRequest({
   }
 
   // Chromium only sends open-ended ranges: "start-"
+  type Match = RegExpMatchArray & { 1: string };
   const match = range.match(/^bytes=(\d+)-$/);
   if (match == null) {
     log.error(`invalid range header: ${range}`);
     return create200Response();
   }
 
-  const startParam = safeParseInteger(match[1]);
+  const [startInput] = match as Match;
+  const startParam = safeParseInteger(startInput);
   if (startParam == null) {
     log.error(`invalid range header: ${range}`);
     return create200Response();

app/main.main.ts

@@ -819,10 +819,14 @@ async function createWindow() {
       maximized: mainWindow.isMaximized(),
       autoHideMenuBar: mainWindow.autoHideMenuBar,
       fullscreen: mainWindow.isFullScreen(),
-      width: size[0],
-      height: size[1],
-      x: position[0],
-      y: position[1],
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      width: size[0]!,
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      height: size[1]!,
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      x: position[0]!,
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      y: position[1]!,
     };
 
     if (
@@ -1565,8 +1569,10 @@ function showPermissionsPopupWindow(forCalling: boolean, forCamera: boolean) {
 
     const size = mainWindow.getSize();
     const options = {
-      width: Math.min(400, size[0]),
-      height: Math.min(150, size[1]),
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      width: Math.min(400, size[0]!),
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      height: Math.min(150, size[1]!),
       resizable: false,
       title: getResolvedMessagesLocale().i18n('icu:allowAccess'),
       titleBarStyle: nonMainTitleBarStyle,

app/menu.std.ts

@@ -9,6 +9,7 @@ import type {
   MenuOptionsType,
   MenuActionsType,
 } from '../ts/types/menu.std.js';
+import { strictAssert } from '../ts/util/assert.std.js';
 
 const { isString } = lodash;
 
@@ -220,6 +221,7 @@ export const createTemplate = (
 
   if (includeSetup) {
     const fileMenu = template[0];
+    strictAssert(fileMenu, 'Missing fileMenu');
 
     if (Array.isArray(fileMenu.submenu)) {
       // These are in reverse order, since we're prepending them one at a time
@@ -265,6 +267,7 @@ function updateForMac(
 
   // Remove About item and separator from Help menu, since they're in the app menu
   const aboutMenu = template[4];
+  strictAssert(aboutMenu, 'Missing aboutMenu');
   if (Array.isArray(aboutMenu.submenu)) {
     aboutMenu.submenu.pop();
     aboutMenu.submenu.pop();
@@ -275,6 +278,7 @@ function updateForMac(
   // Remove preferences, separator, and quit from the File menu, since they're
   // in the app menu
   const fileMenu = template[0];
+  strictAssert(fileMenu, 'Missing fileMenu');
   if (Array.isArray(fileMenu.submenu)) {
     fileMenu.submenu.pop();
     fileMenu.submenu.pop();
@@ -343,6 +347,7 @@ function updateForMac(
   });
 
   const editMenu = template[2];
+  strictAssert(editMenu, 'Missing editMenu');
   if (Array.isArray(editMenu.submenu)) {
     editMenu.submenu.push(
       {
@@ -366,9 +371,11 @@ function updateForMac(
     throw new Error('updateForMac: edit.submenu was not an array!');
   }
 
+  const windowMenu = template[4];
+  strictAssert(windowMenu, 'Missing windowMenu');
   // Replace Window menu
-  // eslint-disable-next-line no-param-reassign
-  template[4].submenu = [
+
+  windowMenu.submenu = [
     {
       label: i18n('icu:windowMenuMinimize'),
       accelerator: 'CmdOrCtrl+M',

build/intl-linter/linter.node.ts

@@ -174,7 +174,8 @@ async function lintMessages() {
     const key = topProp.key.value;
 
     if (process.argv.includes('--test')) {
-      const test = tests[key];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const test = tests[key]!;
       const actualErrors = reports.map(report => report.id);
       deepEqual(actualErrors, test.expectErrors);
       continue;

build/intl-linter/rules/wrapEmoji.std.ts

@@ -37,7 +37,8 @@ export default rule('wrapEmoji', context => {
         return;
       }
 
-      const child = element.children[0];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const child = element.children[0]!;
       if (!isLiteralElement(child)) {
         // non-literal
         context.report(

ts/ConversationController.preload.ts

@@ -1587,9 +1587,7 @@ export class ConversationController {
       `forceRerender: Starting to loop through ${conversations.length} conversations`
     );
 
-    for (let i = 0, max = conversations.length; i < max; i += 1) {
-      const conversation = conversations[i];
-
+    for (const conversation of conversations) {
       if (conversation.cachedProps) {
         conversation.oldCachedProps = conversation.cachedProps;
         conversation.cachedProps = null;

ts/Crypto.node.ts

@@ -357,8 +357,8 @@ export function verifyHmacSha256(
   let result = 0;
 
   for (let i = 0; i < theirMac.byteLength; i += 1) {
-    // eslint-disable-next-line no-bitwise
-    result |= ourMac[i] ^ theirMac[i];
+    // eslint-disable-next-line no-bitwise, @typescript-eslint/no-non-null-assertion
+    result |= ourMac[i]! ^ theirMac[i]!;
   }
   if (result !== 0) {
     throw new Error('Bad MAC');
@@ -482,8 +482,8 @@ function verifyDigest(data: Uint8Array, theirDigest: Uint8Array): void {
   const ourDigest = sha256(data);
   let result = 0;
   for (let i = 0; i < theirDigest.byteLength; i += 1) {
-    // eslint-disable-next-line no-bitwise
-    result |= ourDigest[i] ^ theirDigest[i];
+    // eslint-disable-next-line no-bitwise, @typescript-eslint/no-non-null-assertion
+    result |= ourDigest[i]! ^ theirDigest[i]!;
   }
   if (result !== 0) {
     throw new Error('Bad digest');
@@ -744,7 +744,8 @@ export function getIdentifierHash({
   }
 
   const digest = hash(HashType.size256, identifier);
-  return digest[0];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  return digest[0]!;
 }
 
 export function generateAvatarColor({
@@ -761,8 +762,10 @@ export function generateAvatarColor({
   const hashValue = getIdentifierHash({ aci, e164, pni, groupId });
 
   if (hashValue == null) {
-    return sample(AvatarColors) || AvatarColors[0];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    return sample(AvatarColors) || AvatarColors[0]!;
   }
 
-  return AvatarColors[hashValue % AVATAR_COLOR_COUNT];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  return AvatarColors[hashValue % AVATAR_COLOR_COUNT]!;
 }

ts/Curve.node.ts

@@ -145,10 +145,11 @@ export function setPublicKeyTypeByte(publicKey: Uint8Array): void {
 }
 
 export function clampPrivateKey(privateKey: Uint8Array): void {
-  // eslint-disable-next-line no-bitwise, no-param-reassign
-  privateKey[0] &= 248;
-  // eslint-disable-next-line no-bitwise, no-param-reassign
-  privateKey[31] &= 127;
-  // eslint-disable-next-line no-bitwise, no-param-reassign
-  privateKey[31] |= 64;
+  /* eslint-disable no-bitwise, no-param-reassign */
+  /* eslint-disable @typescript-eslint/no-non-null-assertion */
+  privateKey[0]! &= 248;
+  privateKey[31]! &= 127;
+  privateKey[31]! |= 64;
+  /* eslint-enable no-bitwise, no-param-reassign */
+  /* eslint-enable @typescript-eslint/no-non-null-assertion */
 }

ts/RemoteConfig.dom.ts

@@ -166,7 +166,9 @@ export function onChange(
   listeners[key] = keyListeners;
 
   return () => {
-    listeners[key] = listeners[key].filter(l => l !== fn);
+    if (listeners[key]) {
+      listeners[key] = listeners[key].filter(l => l !== fn);
+    }
   };
 }
 

ts/SignalProtocolStore.preload.ts

@@ -176,8 +176,7 @@ async function _fillCaches<ID, T extends HasIdType<ID>, HydratedType>(
   const items = await itemsPromise;
 
   const cache = new Map<ID, CacheEntryType<T, HydratedType>>();
-  for (let i = 0, max = items.length; i < max; i += 1) {
-    const fromDB = items[i];
+  for (const fromDB of items) {
     const { id } = fromDB;
 
     cache.set(id, {
@@ -304,12 +303,12 @@ export class SignalProtocolStore extends EventEmitter {
           return;
         }
 
-        for (const serviceId of Object.keys(map.value)) {
+        for (const [serviceId, keyPair] of Object.entries(map.value)) {
           strictAssert(
             isServiceIdString(serviceId),
             'Invalid identity key serviceId'
           );
-          const { privKey, pubKey } = map.value[serviceId];
+          const { privKey, pubKey } = keyPair;
           const privateKey = PrivateKey.deserialize(privKey);
           const publicKey = PublicKey.deserialize(pubKey);
           this.#ourIdentityKeys.set(
@@ -327,12 +326,12 @@ export class SignalProtocolStore extends EventEmitter {
           return;
         }
 
-        for (const serviceId of Object.keys(map.value)) {
+        for (const [serviceId, registrationId] of Object.entries(map.value)) {
           strictAssert(
             isServiceIdString(serviceId),
             'Invalid registration id serviceId'
           );
-          this.#ourRegistrationIds.set(serviceId, map.value[serviceId]);
+          this.#ourRegistrationIds.set(serviceId, registrationId);
         }
       })(),
       (async () => {
@@ -1670,10 +1669,7 @@ export class SignalProtocolStore extends EventEmitter {
           `removeSessionsByConversation: Conversation not found: ${identifier}`
         );
 
-        const entries = Array.from(this.sessions.values());
-
-        for (let i = 0, max = entries.length; i < max; i += 1) {
-          const entry = entries[i];
+        for (const entry of this.sessions.values()) {
           if (entry.fromDB.conversationId === id) {
             this.sessions.delete(entry.fromDB.id);
             this.#pendingSessions.delete(entry.fromDB.id);
@@ -1695,10 +1691,7 @@ export class SignalProtocolStore extends EventEmitter {
 
       log.info('removeSessionsByServiceId: deleting sessions for', serviceId);
 
-      const entries = Array.from(this.sessions.values());
-
-      for (let i = 0, max = entries.length; i < max; i += 1) {
-        const entry = entries[i];
+      for (const entry of this.sessions.values()) {
         if (entry.fromDB.serviceId === serviceId) {
           this.sessions.delete(entry.fromDB.id);
           this.#pendingSessions.delete(entry.fromDB.id);

ts/axo/AxoAvatar.dom.stories.tsx

@@ -185,7 +185,8 @@ export function Icons(): JSX.Element {
       {size => (
         <AxoAvatar.Root size={size}>
           <AxoAvatar.Content label={null}>
-            <AxoAvatar.Icon symbol={icons[size % icons.length]} />
+            {/* eslint-disable-next-line @typescript-eslint/no-non-null-assertion */}
+            <AxoAvatar.Icon symbol={icons[size % icons.length]!} />
           </AxoAvatar.Content>
         </AxoAvatar.Root>
       )}

ts/axo/AxoTokens.std.ts

@@ -60,7 +60,8 @@ export namespace AxoTokens {
         Number.isInteger(hash) && hash >= 0,
         'Hash must be positive integer'
       );
-      return ALL_COLOR_NAMES[hash % ALL_COLOR_NAMES.length];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return ALL_COLOR_NAMES[hash % ALL_COLOR_NAMES.length]!;
     }
 
     export type GradientValues = Readonly<{
@@ -96,7 +97,8 @@ export namespace AxoTokens {
         Number.isInteger(hash) && hash >= 0,
         'Hash must be positive integer'
       );
-      return Gradients[hash % Gradients.length];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return Gradients[hash % Gradients.length]!;
     }
 
     export function getGradientsCount(): number {

ts/calling/VideoSupport.preload.ts

@@ -92,7 +92,7 @@ export class GumVideoCapturer {
       return;
     }
 
-    const settings = this.mediaStream.getVideoTracks()?.[0].getSettings();
+    const settings = this.mediaStream.getVideoTracks()?.[0]?.getSettings();
     if (!settings?.width || !settings?.height) {
       return;
     }

ts/calling/findBestMatchingDevice.std.ts

@@ -58,12 +58,5 @@ export function findBestMatchingCameraId(
 
   // By default, pick the first non-IR camera (but allow the user to pick the
   // infrared if they so desire)
-  if (matchingId.length > 0) {
-    return matchingId[0].deviceId;
-  }
-  if (nonInfrared.length > 0) {
-    return nonInfrared[0].deviceId;
-  }
-
-  return undefined;
+  return matchingId[0]?.deviceId ?? nonInfrared[0]?.deviceId;
 }

ts/components/AddUserToAnotherGroupModal.dom.tsx

@@ -22,6 +22,7 @@ import { ListView } from './ListView.dom.js';
 import { ListTile } from './ListTile.dom.js';
 import type { ShowToastAction } from '../state/ducks/toast.preload.js';
 import { SizeObserver } from '../hooks/useSizeObserver.dom.js';
+import { strictAssert } from '../util/assert.std.js';
 
 const { pick } = lodash;
 
@@ -111,6 +112,7 @@ export function AddUserToAnotherGroupModal({
   const handleGetRow = React.useCallback(
     (idx: number): GroupListItemConversationType => {
       const convo = filteredConversations[idx];
+      strictAssert(convo, 'Missing conversation');
 
       // these are always populated in the case of a group
       const memberships = convo.memberships ?? [];

ts/components/AnnouncementsOnlyGroupBanner.dom.tsx

@@ -12,11 +12,12 @@ import type { PreferredBadgeSelectorType } from '../state/selectors/badges.prelo
 import { tw } from '../axo/tw.dom.js';
 import type { AdminMembershipType } from '../state/selectors/conversations.dom.js';
 import { UserText } from './UserText.dom.js';
+import type { ContactNameColorType } from '../types/Colors.std.js';
 
 type PropsType = {
   getPreferredBadge: PreferredBadgeSelectorType;
   groupAdmins: Array<AdminMembershipType>;
-  memberColors: Map<string, string>;
+  memberColors: Map<string, ContactNameColorType>;
   i18n: LocalizerType;
   showConversation: ShowConversationType;
   theme: ThemeType;

ts/components/Avatar.dom.stories.tsx

@@ -109,7 +109,8 @@ Default.play = async (context: any) => {
   const { args, canvasElement } = context;
   const canvas = within(canvasElement);
   const [avatar] = canvas.getAllByRole('button');
-  await userEvent.click(avatar);
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  await userEvent.click(avatar!);
   await expect(args.onClick).toHaveBeenCalled();
 };
 

ts/components/BadgeDialog.dom.tsx

@@ -78,7 +78,8 @@ function BadgeDialogWithBadges({
     currentBadgeIndex = 0;
     currentBadge = firstBadge;
   } else {
-    currentBadge = badges[currentBadgeIndex];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    currentBadge = badges[currentBadgeIndex]!;
   }
 
   const setCurrentBadgeIndex = (index: number): void => {

ts/components/CallManager.dom.stories.tsx

@@ -36,6 +36,14 @@ import { allRemoteParticipants } from './CallScreen.dom.stories.js';
 
 const { i18n } = window.SignalContext;
 
+const [participant1, participant2, participant3, participant4] =
+  allRemoteParticipants as [
+    GroupCallRemoteParticipantType,
+    GroupCallRemoteParticipantType,
+    GroupCallRemoteParticipantType,
+    GroupCallRemoteParticipantType,
+  ];
+
 const getConversation = () =>
   getDefaultConversation({
     id: '3051234567',
@@ -344,7 +352,7 @@ export function CallLinkLobbyParticipants1Known1Unknown(): React.JSX.Element {
     <CallManager
       {...createProps({
         activeCall: getActiveCallForCallLink({
-          peekedParticipants: [allRemoteParticipants[0], getUnknownContact()],
+          peekedParticipants: [participant1, getUnknownContact()],
         }),
         callLink: FAKE_CALL_LINK,
       })}
@@ -359,7 +367,7 @@ export function CallLinkLobbyParticipants1Known2Unknown(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           peekedParticipants: [
             getUnknownContact(),
-            allRemoteParticipants[0],
+            participant1,
             getUnknownContact(),
           ],
         }),
@@ -370,9 +378,7 @@ export function CallLinkLobbyParticipants1Known2Unknown(): React.JSX.Element {
 }
 
 export function CallLinkLobbyParticipants1Known12Unknown(): React.JSX.Element {
-  const peekedParticipants: Array<ConversationType> = [
-    allRemoteParticipants[0],
-  ];
+  const peekedParticipants: Array<ConversationType> = [participant1];
   for (let n = 12; n > 0; n -= 1) {
     peekedParticipants.push(getUnknownContact());
   }
@@ -412,8 +418,8 @@ export function CallLinkWithJoinRequestsOne(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
-          pendingParticipants: [allRemoteParticipants[1]],
+          peekedParticipants: [participant1],
+          pendingParticipants: [participant2],
           showParticipantsList: false,
         }),
         callLink: FAKE_CALL_LINK_WITH_ADMIN_KEY,
@@ -429,7 +435,7 @@ export function CallLinkWithJoinRequestsTwo(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: allRemoteParticipants.slice(1, 3),
           showParticipantsList: false,
         }),
@@ -446,7 +452,7 @@ export function CallLinkWithJoinRequestsMany(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: allRemoteParticipants.slice(1, 11),
           showParticipantsList: false,
         }),
@@ -463,11 +469,11 @@ export function CallLinkWithJoinRequestUnknownContact(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: [
             getUnknownContact(),
-            allRemoteParticipants[1],
-            allRemoteParticipants[2],
+            participant2,
+            participant3,
           ],
           showParticipantsList: false,
         }),
@@ -484,9 +490,9 @@ export function CallLinkWithJoinRequestsSystemContact(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: [
-            { ...allRemoteParticipants[1], name: 'My System Contact Friend' },
+            { ...participant2, name: 'My System Contact Friend' },
           ],
           showParticipantsList: false,
         }),
@@ -503,11 +509,11 @@ export function CallLinkWithJoinRequestsSystemContactMany(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: [
-            { ...allRemoteParticipants[1], name: 'My System Contact Friend' },
-            allRemoteParticipants[2],
-            allRemoteParticipants[3],
+            { ...participant2, name: 'My System Contact Friend' },
+            participant3,
+            participant4,
           ],
           showParticipantsList: false,
         }),
@@ -524,7 +530,7 @@ export function CallLinkWithJoinRequestsParticipantsOpen(): React.JSX.Element {
         activeCall: getActiveCallForCallLink({
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
-          peekedParticipants: [allRemoteParticipants[0]],
+          peekedParticipants: [participant1],
           pendingParticipants: allRemoteParticipants.slice(1, 4),
         }),
         callLink: FAKE_CALL_LINK_WITH_ADMIN_KEY,
@@ -541,7 +547,7 @@ export function CallLinkWithUnknownContacts(): React.JSX.Element {
           connectionState: GroupCallConnectionState.Connected,
           joinState: GroupCallJoinState.Joined,
           remoteParticipants: [
-            allRemoteParticipants[0],
+            participant1,
             getUnknownParticipant(),
             getUnknownParticipant(),
           ],

ts/components/CallReactionBurstEmoji.dom.tsx

@@ -40,7 +40,8 @@ export function CallReactionBurstEmoji({
     (index: number) => {
       return {
         key: uuid(),
-        value: values[index % values.length],
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        value: values[index % values.length]!,
         springConfig: {
           mass: random(10, 20),
           tension: random(45, 60),

ts/components/CallScreen.dom.stories.tsx

@@ -36,6 +36,7 @@ import { fakeGetGroupCallVideoFrameSource } from '../test-helpers/fakeGetGroupCa
 import { CallingToastProvider, useCallingToasts } from './CallingToast.dom.js';
 import type { CallingImageDataCache } from './CallManager.dom.js';
 import { MINUTE } from '../util/durations/index.std.js';
+import { strictAssert } from '../util/assert.std.js';
 
 const { sample, shuffle, times } = lodash;
 
@@ -542,7 +543,7 @@ export const allRemoteParticipants = times(MAX_PARTICIPANTS).map(index => {
           : ''
       } ${index + 1}`,
     }),
-  };
+  } satisfies GroupCallRemoteParticipantType;
 });
 
 export function GroupCallManyPaginated(): React.JSX.Element {
@@ -851,6 +852,7 @@ export function GroupCallReactionsManyInOrder(): React.JSX.Element {
       DEFAULT_PREFERRED_REACTION_EMOJI[
         i % DEFAULT_PREFERRED_REACTION_EMOJI.length
       ];
+    strictAssert(value, 'Missing value');
     return { timestamp, demuxId, value };
   });
   const [props] = React.useState(
@@ -886,7 +888,9 @@ function useReactionsEmitter({
         const participantIndex = Math.floor(
           Math.random() * call.remoteParticipants.length
         );
-        const { demuxId } = call.remoteParticipants[participantIndex];
+        const participant = call.remoteParticipants[participantIndex];
+        strictAssert(participant, 'Missing participant');
+        const { demuxId } = participant;
 
         const reactions: ActiveCallReactionsType = [
           ...(state.reactions ?? []).filter(
@@ -986,9 +990,11 @@ function useHandRaiser(
         );
 
         const raisedHands = new Set(
-          participantIndices.map(
-            index => call.remoteParticipants[index].demuxId
-          )
+          participantIndices.map(index => {
+            const participant = call.remoteParticipants[index];
+            strictAssert(participant, 'Missing participant');
+            return participant.demuxId;
+          })
         );
 
         return {

ts/components/CallScreen.dom.tsx

@@ -483,7 +483,8 @@ export function CallScreen({
       isRinging =
         activeCall.outgoingRing &&
         !activeCall.remoteParticipants.length &&
-        !(groupMembers?.length === 1 && groupMembers[0].id === me.id);
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        !(groupMembers?.length === 1 && groupMembers[0]!.id === me.id);
       hasCallStarted = activeCall.joinState !== GroupCallJoinState.NotJoined;
       participantCount = activeCall.remoteParticipants.length + 1;
       conversationsByDemuxId = activeCall.conversationsByDemuxId;

ts/components/CallingDeviceSelection.dom.tsx

@@ -80,7 +80,8 @@ function createAudioChangeHandler(
   return (value: string): void => {
     changeIODevice({
       type,
-      selectedDevice: devices[Number(value)],
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      selectedDevice: devices[Number(value)]!,
     });
   };
 }

ts/components/CallingPendingParticipants.dom.stories.tsx

@@ -7,12 +7,18 @@ import type { Meta } from '@storybook/react';
 import type { PropsType } from './CallingPendingParticipants.dom.js';
 import { CallingPendingParticipants } from './CallingPendingParticipants.dom.js';
 import { allRemoteParticipants } from './CallScreen.dom.stories.js';
+import { strictAssert } from '../util/assert.std.js';
 
 const { i18n } = window.SignalContext;
 
+strictAssert(allRemoteParticipants[0], 'Missing allRemoteParticipants[0]');
+strictAssert(allRemoteParticipants[1], 'Missing allRemoteParticipants[1]');
+const participant1 = allRemoteParticipants[0];
+const participant2 = allRemoteParticipants[1];
+
 const createProps = (storyProps: Partial<PropsType> = {}): PropsType => ({
   i18n,
-  participants: [allRemoteParticipants[0], allRemoteParticipants[1]],
+  participants: [participant1, participant2],
   approveUser: action('approve-user'),
   batchUserAction: action('batch-user-action'),
   denyUser: action('deny-user'),
@@ -32,7 +38,7 @@ export function One(): React.JSX.Element {
   return (
     <CallingPendingParticipants
       {...createProps({
-        participants: [allRemoteParticipants[0]],
+        participants: [participant1],
       })}
     />
   );
@@ -83,7 +89,7 @@ export function ExpandedOne(): React.JSX.Element {
     <CallingPendingParticipants
       {...createProps({
         defaultIsExpanded: true,
-        participants: [allRemoteParticipants[0]],
+        participants: [participant1],
       })}
     />
   );

ts/components/CallingPip.dom.tsx

@@ -204,7 +204,7 @@ export function CallingPip({
         distanceToRightEdge = innerWidth - (offsetX + width);
       }
 
-      const snapCandidates: Array<SnapCandidate> = [
+      const snapCandidates = [
         {
           mode: PositionMode.SnapToLeft,
           distanceToEdge: distanceToLeftEdge,
@@ -221,7 +221,7 @@ export function CallingPip({
           mode: PositionMode.SnapToBottom,
           distanceToEdge: innerHeight - (offsetY + height),
         },
-      ];
+      ] as const satisfies Array<SnapCandidate>;
 
       // This fallback is mostly for TypeScript, because `minBy` says it can return
       //   `undefined`.
@@ -245,7 +245,7 @@ export function CallingPip({
           });
           break;
         default:
-          throw missingCaseError(snapTo.mode);
+          throw missingCaseError(snapTo);
       }
     }
   }, [height, isRTL, positionState, setPositionState, width]);

ts/components/CallingPreCallInfo.dom.stories.tsx

@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
-import lodash from 'lodash';
 import type { Meta } from '@storybook/react';
 import { getDefaultConversation } from '../test-helpers/getDefaultConversation.std.js';
 import type { PropsType } from './CallingPreCallInfo.dom.js';
@@ -12,8 +11,6 @@ import { generateAci } from '../types/ServiceId.std.js';
 import { FAKE_CALL_LINK } from '../test-helpers/fakeCallLink.std.js';
 import { callLinkToConversation } from '../util/callLinks.std.js';
 
-const { times } = lodash;
-
 const { i18n } = window.SignalContext;
 const getDefaultGroupConversation = () =>
   getDefaultConversation({
@@ -23,7 +20,14 @@ const getDefaultGroupConversation = () =>
     title: 'Tahoe Trip',
     type: 'group',
   });
-const otherMembers = times(6, () => getDefaultConversation());
+const otherMembers = [
+  getDefaultConversation(),
+  getDefaultConversation(),
+  getDefaultConversation(),
+  getDefaultConversation(),
+  getDefaultConversation(),
+  getDefaultConversation(),
+] as const;
 
 const getUnknownContact = (): ConversationType => ({
   acceptedMessageRequest: false,

ts/components/CallingPreCallInfo.dom.tsx

@@ -50,7 +50,7 @@ export type PropsType = {
   ringMode: RingMode;
 
   // The following should only be set for group conversations.
-  groupMembers?: Array<
+  groupMembers?: ReadonlyArray<
     Pick<
       ConversationType,
       'id' | 'firstName' | 'systemGivenName' | 'systemNickname' | 'title'
@@ -58,7 +58,7 @@ export type PropsType = {
   >;
   isCallFull?: boolean;
   isConnecting?: boolean;
-  peekedParticipants?: Array<PeekedParticipantType>;
+  peekedParticipants?: ReadonlyArray<PeekedParticipantType>;
 };
 
 export function CallingPreCallInfo({
@@ -110,36 +110,38 @@ export function CallingPreCallInfo({
         }
         return getParticipantName(participant);
       });
+      /* eslint-disable @typescript-eslint/no-non-null-assertion */
       switch (participantNames.length) {
         case 1:
           subtitle = hasYou
             ? i18n('icu:calling__pre-call-info--another-device-in-call')
             : i18n('icu:calling__pre-call-info--1-person-in-call', {
-                first: participantNames[0],
+                first: participantNames[0]!,
               });
           break;
         case 2:
           subtitle = i18n('icu:calling__pre-call-info--2-people-in-call', {
-            first: participantNames[0],
-            second: participantNames[1],
+            first: participantNames[0]!,
+            second: participantNames[1]!,
           });
           break;
         case 3:
           subtitle = i18n('icu:calling__pre-call-info--3-people-in-call', {
-            first: participantNames[0],
-            second: participantNames[1],
-            third: participantNames[2],
+            first: participantNames[0]!,
+            second: participantNames[1]!,
+            third: participantNames[2]!,
           });
           break;
         default:
           subtitle = i18n('icu:calling__pre-call-info--many-people-in-call', {
-            first: participantNames[0],
-            second: participantNames[1],
+            first: participantNames[0]!,
+            second: participantNames[1]!,
             others: participantNames.length - 2,
           });
           break;
       }
     }
+    /* eslint-enable @typescript-eslint/no-non-null-assertion */
   } else {
     let memberNames: Array<string>;
     switch (conversation.type) {
@@ -158,6 +160,7 @@ export function CallingPreCallInfo({
 
     const ring = ringMode === RingMode.WillRing;
 
+    /* eslint-disable @typescript-eslint/no-non-null-assertion */
     switch (memberNames.length) {
       case 0:
         subtitle = i18n('icu:calling__pre-call-info--empty-group');
@@ -165,55 +168,56 @@ export function CallingPreCallInfo({
       case 1: {
         subtitle = ring
           ? i18n('icu:calling__pre-call-info--will-ring-1', {
-              person: memberNames[0],
+              person: memberNames[0]!,
             })
           : i18n('icu:calling__pre-call-info--will-notify-1', {
-              person: memberNames[0],
+              person: memberNames[0]!,
             });
         break;
       }
       case 2: {
         subtitle = ring
           ? i18n('icu:calling__pre-call-info--will-ring-2', {
-              first: memberNames[0],
-              second: memberNames[1],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
             })
           : i18n('icu:calling__pre-call-info--will-notify-2', {
-              first: memberNames[0],
-              second: memberNames[1],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
             });
         break;
       }
       case 3: {
         subtitle = ring
           ? i18n('icu:calling__pre-call-info--will-ring-3', {
-              first: memberNames[0],
-              second: memberNames[1],
-              third: memberNames[2],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
+              third: memberNames[2]!,
             })
           : i18n('icu:calling__pre-call-info--will-notify-3', {
-              first: memberNames[0],
-              second: memberNames[1],
-              third: memberNames[2],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
+              third: memberNames[2]!,
             });
         break;
       }
       default: {
         subtitle = ring
           ? i18n('icu:calling__pre-call-info--will-ring-many', {
-              first: memberNames[0],
-              second: memberNames[1],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
               others: memberNames.length - 2,
             })
           : i18n('icu:calling__pre-call-info--will-notify-many', {
-              first: memberNames[0],
-              second: memberNames[1],
+              first: memberNames[0]!,
+              second: memberNames[1]!,
               others: memberNames.length - 2,
             });
         break;
       }
     }
   }
+  /* eslint-enable @typescript-eslint/no-non-null-assertion */
 
   return (
     <div className="module-CallingPreCallInfo">

ts/components/CallingToast.dom.tsx

@@ -235,7 +235,8 @@ export function CallingToastProvider({
         toast => toast.key === item.key
       );
       const isToastReplacingAnExistingOneAtThisPosition = toastsRemoved.has(
-        previousToasts[enteringItemIndex]
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        previousToasts[enteringItemIndex]!
       );
       return {
         ...transitionFrom,
@@ -275,7 +276,8 @@ export function CallingToastProvider({
         toast => toast.key === item.key
       );
       const isToastBeingReplacedByANewOneAtThisPosition = toastsAdded.has(
-        toasts[leavingItemIndex]
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        toasts[leavingItemIndex]!
       );
       return {
         zIndex: 0,

ts/components/ChatColorPicker.dom.tsx

@@ -196,8 +196,7 @@ export function ChatColorPicker({
               ref={i === 0 ? focusRef : undefined}
             />
           ))}
-          {Object.keys(customColors).map(colorId => {
-            const colorValues = customColors[colorId];
+          {Object.entries(customColors).map(([colorId, colorValues]) => {
             return (
               <CustomColorBubble
                 color={colorValues}

ts/components/CompositionArea.dom.stories.tsx

@@ -12,6 +12,7 @@ import { StorybookThemeContext } from '../../.storybook/StorybookThemeContext.st
 import { fakeDraftAttachment } from '../test-helpers/fakeAttachment.std.js';
 import { landscapeGreenUrl } from '../storybook/Fixtures.std.js';
 import { RecordingState } from '../types/AudioRecorder.std.js';
+import type { ContactNameColorType } from '../types/Colors.std.js';
 import { ContactNameColors, ConversationColors } from '../types/Colors.std.js';
 import { getDefaultConversation } from '../test-helpers/getDefaultConversation.std.js';
 import { PaymentEventKind } from '../types/Payment.std.js';
@@ -44,11 +45,15 @@ const groupAdmins = [
 ];
 const memberColors = new Map(
   groupAdmins
-    .map((admin, i): [string, string] | null => {
+    .map((admin, i): [string, ContactNameColorType] | null => {
       if (!admin.member.id) {
         return null;
       }
-      return [admin.member.id?.toString(), ContactNameColors[i]];
+      return [
+        admin.member.id?.toString(),
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        ContactNameColors[i % ContactNameColors.length]!,
+      ];
     })
     .filter(isNotNil)
 );

ts/components/CompositionArea.dom.tsx

@@ -91,6 +91,7 @@ import type { PollCreateType } from '../types/Polls.dom.js';
 import { PollCreateModal } from './PollCreateModal.dom.js';
 import { useDocumentKeyDown } from '../hooks/useDocumentKeyDown.dom.js';
 import { hasDraft } from '../util/hasDraft.std.js';
+import type { ContactNameColorType } from '../types/Colors.std.js';
 
 export type OwnProps = Readonly<{
   acceptedMessageRequest: boolean | null;
@@ -139,7 +140,7 @@ export type OwnProps = Readonly<{
   lastEditableMessageId: string | null;
   recordingState: RecordingState;
   messageCompositionId: string;
-  memberColors: Map<string, string>;
+  memberColors: Map<string, ContactNameColorType>;
   shouldHidePopovers: boolean | null;
   isMuted: boolean;
   isSmsOnlyOrUnregistered: boolean | null;
@@ -1101,7 +1102,11 @@ export const CompositionArea = memo(function CompositionArea({
     return renderSmartCompositionRecording();
   }
 
-  if (draftAttachments.length === 1 && isVoiceMessage(draftAttachments[0])) {
+  if (
+    draftAttachments.length === 1 &&
+    draftAttachments[0] != null &&
+    isVoiceMessage(draftAttachments[0])
+  ) {
     const voiceNoteAttachment = draftAttachments[0];
 
     if (!voiceNoteAttachment.pending && voiceNoteAttachment.url) {

ts/components/CompositionInput.dom.tsx

@@ -934,9 +934,9 @@ export function CompositionInput(props: Props): React.ReactElement {
               key: tabKey,
               handler: () => callbacksRef.current.onTab(),
             });
-            const ourHandler = quill.keyboard.bindings[tabKey].pop();
+            const ourHandler = quill.keyboard.bindings[tabKey]?.pop();
             if (ourHandler) {
-              quill.keyboard.bindings[tabKey].unshift(ourHandler);
+              quill.keyboard.bindings[tabKey]?.unshift(ourHandler);
             }
 
             const emojiCompletion = quill.getModule('emojiCompletion');

ts/components/ContactPills.dom.stories.tsx

@@ -2,7 +2,6 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import React from 'react';
-import lodash from 'lodash';
 
 import { action } from '@storybook/addon-actions';
 
@@ -13,8 +12,6 @@ import { ContactPill } from './ContactPill.dom.js';
 import { gifUrl } from '../storybook/Fixtures.std.js';
 import { getDefaultConversation } from '../test-helpers/getDefaultConversation.std.js';
 
-const { times } = lodash;
-
 const { i18n } = window.SignalContext;
 
 export default {
@@ -23,15 +20,15 @@ export default {
 
 type ContactType = Omit<ContactPillPropsType, 'i18n' | 'onClickRemove'>;
 
-const contacts: Array<ContactType> = times(50, index =>
-  getDefaultConversation({
+function createContact(index: number) {
+  return getDefaultConversation({
     id: `contact-${index}`,
     name: `Contact ${index}`,
     phoneNumber: '(202) 555-0001',
     profileName: `C${index}`,
     title: `Contact ${index}`,
-  })
-);
+  });
+}
 
 const contactPillProps = (
   overrideProps?: ContactType
@@ -67,9 +64,9 @@ export function OneContact(): React.JSX.Element {
 export function ThreeContacts(): React.JSX.Element {
   return (
     <ContactPills>
-      <ContactPill {...contactPillProps(contacts[0])} />
-      <ContactPill {...contactPillProps(contacts[1])} />
-      <ContactPill {...contactPillProps(contacts[2])} />
+      <ContactPill {...contactPillProps(createContact(0))} />
+      <ContactPill {...contactPillProps(createContact(1))} />
+      <ContactPill {...contactPillProps(createContact(2))} />
     </ContactPills>
   );
 }
@@ -77,16 +74,16 @@ export function ThreeContacts(): React.JSX.Element {
 export function FourContactsOneWithALongName(): React.JSX.Element {
   return (
     <ContactPills>
-      <ContactPill {...contactPillProps(contacts[0])} />
+      <ContactPill {...contactPillProps(createContact(0))} />
       <ContactPill
         {...contactPillProps({
-          ...contacts[1],
+          ...createContact(1),
           title:
             'Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso',
         })}
       />
-      <ContactPill {...contactPillProps(contacts[2])} />
-      <ContactPill {...contactPillProps(contacts[3])} />
+      <ContactPill {...contactPillProps(createContact(2))} />
+      <ContactPill {...contactPillProps(createContact(3))} />
     </ContactPills>
   );
 }
@@ -94,8 +91,8 @@ export function FourContactsOneWithALongName(): React.JSX.Element {
 export function FiftyContacts(): React.JSX.Element {
   return (
     <ContactPills>
-      {contacts.map(contact => (
-        <ContactPill key={contact.id} {...contactPillProps(contact)} />
+      {Array.from({ length: 50 }, (_, index) => (
+        <ContactPill key={index} {...contactPillProps(createContact(index))} />
       ))}
     </ContactPills>
   );

ts/components/ContextMenu.dom.tsx

@@ -191,7 +191,8 @@ export function ContextMenu<T>({
 
     if (ev.key === 'Enter') {
       if (focusedIndex !== undefined) {
-        const focusedOption = menuOptions[focusedIndex];
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        const focusedOption = menuOptions[focusedIndex]!;
         focusedOption.onClick(focusedOption.value);
       }
       setIsMenuShowing(false);

ts/components/ConversationList.dom.stories.tsx

@@ -27,7 +27,7 @@ export default {
   args: {},
 } satisfies Meta<PropsType>;
 
-const defaultConversations: Array<ConversationListItemPropsType> = [
+const defaultConversations = [
   getDefaultConversation({
     id: 'fred-convo',
     title: 'Fred Willard',
@@ -48,7 +48,7 @@ const defaultConversations: Array<ConversationListItemPropsType> = [
       'Pablo Diego José Francisco de Paula Juan Nepomuceno María de los Remedios Cipriano de la Santísima Trinidad Ruiz y Picasso',
   }),
   getDefaultConversation(),
-];
+] as const satisfies Array<ConversationListItemPropsType>;
 
 function Wrapper({
   rows,

ts/components/EditHistoryMessagesModal.dom.tsx

@@ -23,6 +23,7 @@ import { TimelineDateHeader } from './conversation/TimelineDateHeader.dom.js';
 import { AxoContextMenu } from '../axo/AxoContextMenu.dom.js';
 import { drop } from '../util/drop.std.js';
 import type { AxoMenuBuilder } from '../axo/AxoMenuBuilder.dom.js';
+import { strictAssert } from '../util/assert.std.js';
 
 const { noop } = lodash;
 
@@ -115,6 +116,7 @@ export function EditHistoryMessagesModal({
   >({});
 
   const [currentMessage, ...pastEdits] = editHistoryMessages;
+  strictAssert(currentMessage, 'Missing currentMessage');
   const currentMessageId = `${currentMessage.id}.${currentMessage.timestamp}`;
 
   let previousItem = currentMessage;

ts/components/GroupCallRemoteParticipants.dom.tsx

@@ -192,9 +192,12 @@ export function GroupCallRemoteParticipants({
     }
 
     if (isInSpeakerView) {
+      const firstParticipiant = prioritySortedParticipants[0];
+      strictAssert(firstParticipiant, 'Missing firstParticipiant');
+
       return [
         {
-          rows: [[prioritySortedParticipants[0]]],
+          rows: [[firstParticipiant]],
           hasSpaceRemaining: false,
           numParticipants: 1,
         },
@@ -222,7 +225,7 @@ export function GroupCallRemoteParticipants({
 
   const isSomeonePresenting =
     prioritySortedParticipants.length &&
-    prioritySortedParticipants[0].presenting;
+    prioritySortedParticipants[0]?.presenting;
 
   // Make sure we're not on a page that no longer exists (e.g. if people left the call)
   if (
@@ -750,6 +753,10 @@ function getGridParticipantsByPage({
               PARTICIPANTS_TO_REMOVE_PER_ATTEMPT.length - 1
             )
           ];
+        strictAssert(
+          numLeastPrioritizedParticipantsToRemove,
+          'Missing numLeastPrioritizedParticipantsToRemove'
+        );
 
         const leastPrioritizedParticipantIds = new Set(
           priorityParticipantsOnNextPage
@@ -804,7 +811,9 @@ function getGridParticipantsByPage({
 
     // Add a previous page tile if needed
     if (pages.length > 0) {
-      nextPageTiles.rows[0].unshift({
+      const firstRow = nextPageTiles.rows[0];
+      strictAssert(firstRow, 'Missing firstRow');
+      firstRow.unshift({
         isPaginationButton: true,
         paginationButtonType: 'prev',
         videoAspectRatio: PAGINATION_BUTTON_ASPECT_RATIO,
@@ -877,11 +886,11 @@ function getNextPage({
   // Initialize fresh page with empty first row
   const rows: Array<Array<GroupCallRemoteParticipantType>> = [[]];
   let row = rows[0];
+  strictAssert(row, 'Missing row');
   let numParticipants = 0;
 
   // Start looping through participants and adding them to the rows one-by-one
-  for (let i = 0; i < participants.length; i += 1) {
-    const participant = participants[i];
+  for (const [i, participant] of participants.entries()) {
     const isLastParticipant =
       !isSubsetOfAllParticipants && i === participants.length - 1;
 

ts/components/GroupMembersNames.dom.tsx

@@ -54,33 +54,35 @@ function MemberList({
   i18n: LocalizerType;
   onOtherMembersClick?: () => void;
 }): React.JSX.Element {
+  const [member1, member2, member3] = firstThreeMemberNames;
+
   if (areWeInGroup) {
-    if (otherMemberNames.length === 0) {
+    if (member1 == null) {
       return (
         <I18n i18n={i18n} id="icu:ConversationHero--group-members-only-you" />
       );
     }
 
-    if (otherMemberNames.length === 1) {
+    if (member2 == null) {
       return (
         <I18n
           i18n={i18n}
           id="icu:ConversationHero--group-members-one-and-you"
           components={{
-            member: firstThreeMemberNames[0],
+            member: member1,
           }}
         />
       );
     }
 
-    if (otherMemberNames.length === 2) {
+    if (member3 == null) {
       return (
         <I18n
           i18n={i18n}
           id="icu:ConversationHero--group-members-two-and-you"
           components={{
-            member1: firstThreeMemberNames[0],
-            member2: firstThreeMemberNames[1],
+            member1,
+            member2,
           }}
         />
       );
@@ -93,9 +95,9 @@ function MemberList({
         i18n={i18n}
         id="icu:ConversationHero--group-members-other-and-you"
         components={{
-          member1: firstThreeMemberNames[0],
-          member2: firstThreeMemberNames[1],
-          member3: firstThreeMemberNames[2],
+          member1,
+          member2,
+          member3,
           clickable: (parts: ReactNode) =>
             renderClickableButton(parts, onOtherMembersClick),
           remainingCount,
@@ -106,30 +108,30 @@ function MemberList({
 
   // When the user is not in the group
 
-  if (otherMemberNames.length === 0) {
+  if (member1 == null) {
     return <I18n i18n={i18n} id="icu:ConversationHero--group-members-zero" />;
   }
 
-  if (otherMemberNames.length === 1) {
+  if (member2 == null) {
     return (
       <I18n
         i18n={i18n}
         id="icu:ConversationHero--group-members-one"
         components={{
-          member: firstThreeMemberNames[0],
+          member: member1,
         }}
       />
     );
   }
 
-  if (otherMemberNames.length === 2) {
+  if (member3 == null) {
     return (
       <I18n
         i18n={i18n}
         id="icu:ConversationHero--group-members-two"
         components={{
-          member1: firstThreeMemberNames[0],
-          member2: firstThreeMemberNames[1],
+          member1,
+          member2,
         }}
       />
     );
@@ -141,9 +143,9 @@ function MemberList({
         i18n={i18n}
         id="icu:ConversationHero--group-members-three"
         components={{
-          member1: firstThreeMemberNames[0],
-          member2: firstThreeMemberNames[1],
-          member3: firstThreeMemberNames[2],
+          member1,
+          member2,
+          member3,
         }}
       />
     );
@@ -156,9 +158,9 @@ function MemberList({
       i18n={i18n}
       id="icu:ConversationHero--group-members-other"
       components={{
-        member1: firstThreeMemberNames[0],
-        member2: firstThreeMemberNames[1],
-        member3: firstThreeMemberNames[2],
+        member1,
+        member2,
+        member3,
         clickable: (parts: ReactNode) =>
           renderClickableButton(parts, onOtherMembersClick),
         remainingCount,

ts/components/IncomingCallBar.dom.tsx

@@ -123,6 +123,7 @@ function GroupCallMessage({
     .map(member => <UserText text={getParticipantName(member)} />);
   const ringerNode = <UserText text={getParticipantName(ringer)} />;
 
+  /* eslint-disable @typescript-eslint/no-non-null-assertion */
   switch (otherMembersRung.length) {
     case 0:
       return (
@@ -139,7 +140,8 @@ function GroupCallMessage({
           i18n={i18n}
           components={{
             ringer: ringerNode,
-            otherMember: first,
+
+            otherMember: first!,
           }}
         />
       );
@@ -150,8 +152,8 @@ function GroupCallMessage({
           i18n={i18n}
           components={{
             ringer: ringerNode,
-            first,
-            second,
+            first: first!,
+            second: second!,
           }}
         />
       );
@@ -162,8 +164,8 @@ function GroupCallMessage({
           i18n={i18n}
           components={{
             ringer: ringerNode,
-            first,
-            second,
+            first: first!,
+            second: second!,
           }}
         />
       );
@@ -174,13 +176,14 @@ function GroupCallMessage({
           i18n={i18n}
           components={{
             ringer: ringerNode,
-            first,
-            second,
+            first: first!,
+            second: second!,
             remaining: otherMembersRung.length - 2,
           }}
         />
       );
   }
+  /* eslint-enable @typescript-eslint/no-non-null-assertion */
 }
 
 export function IncomingCallBar(props: PropsType): React.JSX.Element | null {

ts/components/LeftPane.dom.stories.tsx

@@ -51,7 +51,7 @@ export default {
   args: {},
 } satisfies Meta<PropsType>;
 
-const defaultConversations: Array<ConversationType> = [
+const defaultConversations = [
   getDefaultConversation({
     id: 'fred-convo',
     title: 'Fred Willard',
@@ -61,7 +61,7 @@ const defaultConversations: Array<ConversationType> = [
     isSelected: true,
     title: 'Marc Barraca',
   }),
-];
+] as const satisfies Array<ConversationType>;
 
 const defaultSearchProps = {
   filterByUnread: false,

ts/components/Lightbox.dom.tsx

@@ -35,6 +35,7 @@ import { formatFileSize } from '../util/formatFileSize.std.js';
 import { SECOND } from '../util/durations/index.std.js';
 import { Toast } from './Toast.dom.js';
 import { isAbortError } from '../util/isAbortError.std.js';
+import { strictAssert } from '../util/assert.std.js';
 
 const { noop } = lodash;
 
@@ -146,6 +147,7 @@ export function Lightbox({
   >();
 
   const currentItem = media[selectedIndex];
+
   const attachment = currentItem?.attachment;
   const url = attachment?.url;
   const incrementalUrl = attachment?.incrementalUrl;
@@ -242,6 +244,7 @@ export function Lightbox({
       event.preventDefault();
 
       const mediaItem = media[selectedIndex];
+      strictAssert(mediaItem, 'Missing mediaItem');
       const { attachment: attachmentToSave, message, index } = mediaItem;
 
       saveAttachment(attachmentToSave, message.sentAt, index + 1);
@@ -261,6 +264,8 @@ export function Lightbox({
 
     closeLightbox();
     const mediaItem = media[selectedIndex];
+    strictAssert(mediaItem, 'Missing mediaItem');
+
     toggleForwardMessagesModal({
       type: ForwardMessagesModalType.Forward,
       messageIds: [mediaItem.message.id],
@@ -473,6 +478,7 @@ export function Lightbox({
   const handleTouchStart = useCallback(
     (ev: TouchEvent) => {
       const [touch] = ev.touches;
+      strictAssert(touch, 'Missing touch');
 
       dragCacheRef.current = {
         startX: touch.clientX,
@@ -493,6 +499,7 @@ export function Lightbox({
       }
 
       const [touch] = ev.touches;
+      strictAssert(touch, 'Missing touch');
 
       const deltaX = touch.clientX - dragCache.startX;
       const deltaY = touch.clientY - dragCache.startY;
@@ -724,7 +731,7 @@ export function Lightbox({
               ref={focusRef}
             >
               <div className="Lightbox__header">
-                {getConversation ? (
+                {getConversation && currentItem != null ? (
                   <LightboxHeader
                     getConversation={getConversation}
                     i18n={i18n}

ts/components/MyStories.dom.stories.tsx

@@ -54,7 +54,8 @@ const interactionTest: PlayFunction<ReactRenderer, PropsType> = async ({
 }) => {
   const canvas = within(canvasElement);
   const [btnDownload] = canvas.getAllByLabelText('Download story');
-  await userEvent.click(btnDownload);
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  await userEvent.click(btnDownload!);
   await expect(args.onSave).toHaveBeenCalled();
 
   const btnBack = canvas.getByText('Back');
@@ -63,10 +64,12 @@ const interactionTest: PlayFunction<ReactRenderer, PropsType> = async ({
 
   const [btnCtxMenu] = canvas.getAllByLabelText('Context menu');
 
-  await userEvent.click(btnCtxMenu);
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  await userEvent.click(btnCtxMenu!);
   await sleep(300);
   const [btnFwd] = canvas.getAllByLabelText('Forward');
-  await userEvent.click(btnFwd);
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  await userEvent.click(btnFwd!);
   await expect(args.onForward).toHaveBeenCalled();
 };
 

ts/components/MyStoryButton.dom.tsx

@@ -28,7 +28,8 @@ export type PropsType = {
 };
 
 function getNewestMyStory(story: MyStoryType): StoryViewType {
-  return story.stories[0];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  return story.stories[0]!;
 }
 
 export function MyStoryButton({
@@ -45,7 +46,8 @@ export function MyStoryButton({
   const [active, setActive] = useState(false);
 
   const newestStory = myStories.length
-    ? getNewestMyStory(myStories[0])
+    ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      getNewestMyStory(myStories[0]!)
     : undefined;
 
   const { avatarUrl, color, profileName, title } = me;
@@ -85,7 +87,8 @@ export function MyStoryButton({
   }
 
   const hasMultiple = myStories.length
-    ? myStories[0].stories.length > 1
+    ? // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      myStories[0]!.stories.length > 1
     : false;
 
   const reducedSendStatus: ResolvedSendStatus = myStories.reduce(

ts/components/NewlyCreatedGroupInvitedContactsDialog.dom.stories.tsx

@@ -14,10 +14,10 @@ import { ThemeType } from '../types/Util.std.js';
 
 const { i18n } = window.SignalContext;
 
-const conversations: Array<ConversationType> = [
+const conversations = [
   getDefaultConversation({ title: 'Fred Willard' }),
   getDefaultConversation({ title: 'Marc Barraca' }),
-];
+] as const satisfies Array<ConversationType>;
 
 export default {
   title: 'Components/NewlyCreatedGroupInvitedContactsDialog',

ts/components/NewlyCreatedGroupInvitedContactsDialog.dom.tsx

@@ -29,7 +29,8 @@ export function NewlyCreatedGroupInvitedContactsDialog({
 }: PropsType): React.JSX.Element {
   let body: ReactNode;
   if (contacts.length === 1) {
-    const contact = contacts[0];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const contact = contacts[0]!;
 
     body = (
       <>

ts/components/NotificationProfilesMenu.dom.stories.tsx

@@ -17,6 +17,7 @@ import type { NotificationProfileIdString } from '../types/NotificationProfile.s
 import { HOUR } from '../util/durations/index.std.js';
 import { AxoDropdownMenu } from '../axo/AxoDropdownMenu.dom.js';
 import { AxoButton } from '../axo/AxoButton.dom.js';
+import type { ConversationType } from '../state/ducks/conversations.preload.js';
 
 const { i18n } = window.SignalContext;
 
@@ -25,6 +26,11 @@ const conversations = shuffle([
   ...Array.from(Array(20), getDefaultConversation),
 ]);
 
+const [conversation1, conversation2] = conversations as [
+  ConversationType,
+  ConversationType,
+];
+
 const threeProfiles = [
   {
     id: 'Weekday' as NotificationProfileIdString,
@@ -37,7 +43,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 1800,
@@ -66,7 +72,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 1800,
@@ -95,7 +101,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 1800,
@@ -113,7 +119,7 @@ const threeProfiles = [
     deletedAtTimestampMs: undefined,
     storageNeedsSync: true,
   },
-];
+] as const;
 
 export default {
   title: 'Components/NotificationProfilesMenu',

ts/components/PlaybackRateButton.dom.tsx

@@ -76,7 +76,7 @@ export function PlaybackRateButton({
   };
 
   const label = playbackRate
-    ? playbackRateLabels[playbackRate].toString()
+    ? playbackRateLabels[playbackRate]?.toString()
     : undefined;
 
   return (
@@ -105,7 +105,8 @@ const playbackRates = [1, 1.5, 2, 0.5];
 
 PlaybackRateButton.nextPlaybackRate = (currentRate: number): number => {
   // cycle through the rates
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
   return playbackRates[
     (playbackRates.indexOf(currentRate) + 1) % playbackRates.length
-  ];
+  ]!;
 };

ts/components/PollCreateModal.dom.tsx

@@ -75,7 +75,7 @@ export function PollCreateModal({
       const isLastOption = changedIndex === resultOptions.length - 1;
       const isSecondToLast = changedIndex === resultOptions.length - 2;
       const changedOption = resultOptions[changedIndex];
-      const hasText = changedOption?.value.trim().length > 0;
+      const hasText = (changedOption?.value.trim().length ?? 0) > 0;
       const canAddMore = resultOptions.length < POLL_OPTIONS_MAX_COUNT;
       const canRemove = resultOptions.length > POLL_OPTIONS_MIN_COUNT;
       let removedIndex: number | undefined;

ts/components/Preferences.dom.stories.tsx

@@ -76,6 +76,10 @@ const conversations = shuffle([
   ...Array.from(Array(20), getDefaultConversation),
 ]);
 
+const [conversation1, conversation2] = conversations;
+strictAssert(conversation1, 'Missing conversation1');
+strictAssert(conversation2, 'Missing conversation2');
+
 function conversationSelector(conversationId?: string) {
   strictAssert(conversationId, 'Missing conversation id');
   const found = conversations.find(conversation => {
@@ -734,7 +738,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 1800,
@@ -763,7 +767,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 100,
@@ -792,7 +796,7 @@ const threeProfiles = [
     allowAllCalls: true,
     allowAllMentions: true,
 
-    allowedMembers: new Set([conversations[0].id, conversations[1].id]),
+    allowedMembers: new Set([conversation1.id, conversation2.id]),
     scheduleEnabled: true,
 
     scheduleStartTime: 1800,
@@ -810,7 +814,7 @@ const threeProfiles = [
     deletedAtTimestampMs: undefined,
     storageNeedsSync: true,
   },
-];
+] as const;
 
 NotificationsPageWithThreeProfiles.args = {
   settingsLocation: { page: SettingsPage.Notifications },

ts/components/PreferencesNotificationProfiles.dom.tsx

@@ -243,7 +243,8 @@ const ARGB_BITS = 0xff000000;
 const A100_BACKGROUND_ARGB = 0xffe3e3fe;
 
 function getRandomColor(): number {
-  const colorName = sample(AvatarColors) || AvatarColors[0];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  const colorName = sample(AvatarColors) || AvatarColors[0]!;
   const color = AvatarColorMap.get(colorName);
   if (!color) {
     return A100_BACKGROUND_ARGB; // A100, background, with bits for ARGB

ts/components/ProfileEditor.dom.tsx

@@ -29,7 +29,6 @@ import {
   ConversationDetailsIcon,
   IconType,
 } from './conversation/conversation-details/ConversationDetailsIcon.dom.js';
-import { isWhitespace, trim } from '../util/whitespaceStringUtil.std.js';
 import { UserText } from './UserText.dom.js';
 import { Tooltip, TooltipPlacement } from './Tooltip.dom.js';
 import { offsetDistanceModifier } from '../util/popperUtil.std.js';
@@ -294,9 +293,9 @@ export function ProfileEditor({
       onProfileChanged(
         {
           ...stagedProfile,
-          firstName: trim(stagedProfile.firstName),
+          firstName: stagedProfile.firstName.trim(),
           familyName: stagedProfile.familyName
-            ? trim(stagedProfile.familyName)
+            ? stagedProfile.familyName.trim()
             : undefined,
         },
         {
@@ -376,7 +375,7 @@ export function ProfileEditor({
       !stagedProfile.firstName ||
       (stagedProfile.firstName === fullName.firstName &&
         stagedProfile.familyName === fullName.familyName) ||
-      isWhitespace(stagedProfile.firstName);
+      stagedProfile.firstName.trim() === '';
 
     content = (
       <>

ts/components/SafetyTipsModal.dom.tsx

@@ -56,7 +56,8 @@ export function SafetyTipsModal({
   const [cardWrapperId] = useState(() => uuid());
 
   function getCardIdForPage(pageIndex: number) {
-    return `${cardWrapperId}_${pages[pageIndex].key}`;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    return `${cardWrapperId}_${pages[pageIndex]!.key}`;
   }
 
   const maxPageIndex = pages.length - 1;

ts/components/SharedGroupNames.dom.tsx

@@ -29,6 +29,7 @@ export function SharedGroupNames({
     </strong>
   ));
 
+  /* eslint-disable @typescript-eslint/no-non-null-assertion */
   if (sharedGroupNames.length >= 5) {
     const remainingCount = sharedGroupNames.length - 3;
     return (
@@ -36,9 +37,9 @@ export function SharedGroupNames({
         i18n={i18n}
         id="icu:member-of-more-than-3-groups--multiple-more"
         components={{
-          group1: firstThreeGroups[0],
-          group2: firstThreeGroups[1],
-          group3: firstThreeGroups[2],
+          group1: firstThreeGroups[0]!,
+          group2: firstThreeGroups[1]!,
+          group3: firstThreeGroups[2]!,
           remainingCount,
         }}
       />
@@ -50,9 +51,9 @@ export function SharedGroupNames({
         i18n={i18n}
         id="icu:member-of-more-than-3-groups--one-more"
         components={{
-          group1: firstThreeGroups[0],
-          group2: firstThreeGroups[1],
-          group3: firstThreeGroups[2],
+          group1: firstThreeGroups[0]!,
+          group2: firstThreeGroups[1]!,
+          group3: firstThreeGroups[2]!,
         }}
       />
     );
@@ -63,9 +64,9 @@ export function SharedGroupNames({
         i18n={i18n}
         id="icu:member-of-3-groups"
         components={{
-          group1: firstThreeGroups[0],
-          group2: firstThreeGroups[1],
-          group3: firstThreeGroups[2],
+          group1: firstThreeGroups[0]!,
+          group2: firstThreeGroups[1]!,
+          group3: firstThreeGroups[2]!,
         }}
       />
     );
@@ -76,8 +77,8 @@ export function SharedGroupNames({
         i18n={i18n}
         id="icu:member-of-2-groups"
         components={{
-          group1: firstThreeGroups[0],
-          group2: firstThreeGroups[1],
+          group1: firstThreeGroups[0]!,
+          group2: firstThreeGroups[1]!,
         }}
       />
     );
@@ -88,11 +89,12 @@ export function SharedGroupNames({
         i18n={i18n}
         id="icu:member-of-1-group"
         components={{
-          group: firstThreeGroups[0],
+          group: firstThreeGroups[0]!,
         }}
       />
     );
   }
+  /* eslint-enable @typescript-eslint/no-non-null-assertion */
 
   return <>{i18n('icu:no-groups-in-common')}</>;
 }

ts/components/TextAttachment.dom.tsx

@@ -75,7 +75,7 @@ function getFont(
   textStyle?: TextAttachmentStyleType | null,
   i18n?: LocalizerType
 ): string {
-  const textStyleIndex = Number(textStyle) || 0;
+  const textStyleIndex = textStyle ?? TextAttachmentStyleType.DEFAULT;
   const fontName = getFontNameByTextScript(text, textStyleIndex, i18n);
 
   let fontSize = FONT_SIZE_SMALL;

ts/components/VoiceNotesPlaybackContext.dom.tsx

@@ -122,9 +122,9 @@ async function doComputePeaks(
   ) {
     const channel = data.getChannelData(channelNum);
 
-    for (let sample = 0; sample < channel.length; sample += 1) {
+    for (const [sample, sampleData] of channel.entries()) {
       const i = Math.floor(sample / samplesPerPeak);
-      peaks[i] += channel[sample] ** 2;
+      peaks[i] += sampleData ** 2;
       norms[i] += 1;
     }
   }

ts/components/conversation/AttachmentList.dom.tsx

@@ -97,7 +97,8 @@ export function AttachmentList<
       <div className="module-attachments__rail">
         {attachments.map((attachment, index) => {
           const url = getUrl(attachment);
-          const forUI = attachmentsForUI[index];
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          const forUI = attachmentsForUI[index]!;
 
           const key =
             attachment.clientUuid ||

ts/components/conversation/ContactModal.dom.tsx

@@ -39,6 +39,7 @@ import { AxoSymbol } from '../../axo/AxoSymbol.dom.js';
 import { tw } from '../../axo/tw.dom.js';
 import { strictAssert } from '../../util/assert.std.js';
 import type { RemoveClientType } from '../../types/Calling.std.js';
+import type { ContactNameColorType } from '../../types/Colors.std.js';
 
 const ACCESS_ENUM = Proto.AccessControl.AccessRequired;
 
@@ -52,7 +53,7 @@ export type PropsDataType = {
   contact?: ConversationType;
   contactLabelEmoji: string | undefined;
   contactLabelString: string | undefined;
-  contactNameColor: string | undefined;
+  contactNameColor: ContactNameColorType | undefined;
   conversation?: ConversationType;
   hasStories?: HasStories;
   readonly i18n: LocalizerType;

ts/components/conversation/ConversationView.dom.tsx

@@ -114,8 +114,8 @@ export function ConversationView({
       });
       if (allVisual) {
         const files: Array<File> = [];
-        for (let i = 0; i < items.length; i += 1) {
-          const file = getAsFile(items[i]);
+        for (const item of items) {
+          const file = getAsFile(item);
           if (file) {
             files.push(file);
           }

ts/components/conversation/GroupNotification.dom.tsx

@@ -92,7 +92,8 @@ function GroupNotificationChange({
                 <I18n
                   i18n={i18n}
                   id="icu:joinedTheGroup"
-                  components={{ name: otherPeople[0] }}
+                  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+                  components={{ name: otherPeople[0]! }}
                 />
               ) : (
                 <I18n
@@ -123,7 +124,8 @@ function GroupNotificationChange({
         <I18n
           id="icu:multipleLeftTheGroup"
           i18n={i18n}
-          components={{ name: otherPeople[0] }}
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          components={{ name: otherPeople[0]! }}
         />
       ) : (
         <I18n

ts/components/conversation/GroupV1Migration.dom.tsx

@@ -128,7 +128,8 @@ function renderUsers({
   }
 
   if (members && count === 1) {
-    const contact = <ContactName title={members[0].title} />;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const contact = <ContactName title={members[0]!.title} />;
     return (
       <p>
         {kind === 'invited' && (

ts/components/conversation/ImageGrid.dom.tsx

@@ -23,6 +23,7 @@ import { Image, CurveType } from './Image.dom.js';
 
 import type { LocalizerType, ThemeType } from '../../types/Util.std.js';
 import { AttachmentDetailPill } from './AttachmentDetailPill.dom.js';
+import { strictAssert } from '../../util/assert.std.js';
 
 export type DirectionType = 'incoming' | 'outgoing';
 
@@ -158,10 +159,13 @@ export function ImageGrid({
   );
 
   const showAttachmentOrNoLongerAvailableToast = React.useCallback(
-    (attachmentIndex: number) =>
-      attachments[attachmentIndex].isPermanentlyUndownloadable
+    (attachmentIndex: number) => {
+      const attachment = attachments[attachmentIndex];
+      strictAssert(attachment, 'Missing attachment');
+      return attachment.isPermanentlyUndownloadable
         ? showMediaNoLongerAvailableToast
-        : showVisualAttachment,
+        : showVisualAttachment;
+    },
     [attachments, showVisualAttachment, showMediaNoLongerAvailableToast]
   );
 
@@ -189,8 +193,10 @@ export function ImageGrid({
   });
 
   if (attachments.length === 1 || !areAllAttachmentsVisual(attachments)) {
+    const [attachment] = attachments;
+    strictAssert(attachment, 'Missing attachment');
     const { height, width } = getImageDimensionsForTimeline(
-      attachments[0],
+      attachment,
       isSticker ? stickerSize : undefined
     );
 
@@ -203,10 +209,10 @@ export function ImageGrid({
         )}
       >
         <Image
-          alt={getAlt(attachments[0], i18n)}
+          alt={getAlt(attachment, i18n)}
           i18n={i18n}
           theme={theme}
-          blurHash={attachments[0].blurHash}
+          blurHash={attachment.blurHash}
           bottomOverlay={withBottomOverlay}
           noBorder={isSticker}
           noBackground={isSticker}
@@ -214,13 +220,11 @@ export function ImageGrid({
           curveTopRight={curveTopRight}
           curveBottomLeft={curveBottomLeft}
           curveBottomRight={curveBottomRight}
-          attachment={attachments[0]}
-          playIconOverlay={isVideoAttachment(attachments[0])}
+          attachment={attachment}
+          playIconOverlay={isVideoAttachment(attachment)}
           height={height}
           width={width}
-          url={
-            getUrl(attachments[0]) ?? attachments[0].thumbnailFromBackup?.url
-          }
+          url={getUrl(attachment) ?? attachment.thumbnailFromBackup?.url}
           tabIndex={tabIndex}
           showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
           showVisualAttachment={showAttachmentOrNoLongerAvailableToast(0)}
@@ -234,23 +238,26 @@ export function ImageGrid({
   }
 
   if (attachments.length === 2) {
+    const [attachment1, attachment2] = attachments;
+    strictAssert(attachment1, 'Missing attachment 1');
+    strictAssert(attachment2, 'Missing attachment 2');
     return (
       <div className="module-image-grid">
         <Image
-          alt={getAlt(attachments[0], i18n)}
+          alt={getAlt(attachment1, i18n)}
           i18n={i18n}
           theme={theme}
-          attachment={attachments[0]}
-          blurHash={attachments[0].blurHash}
+          attachment={attachment1}
+          blurHash={attachment1.blurHash}
           bottomOverlay={withBottomOverlay}
           noBorder={false}
           curveTopLeft={curveTopLeft}
           curveBottomLeft={curveBottomLeft}
-          playIconOverlay={isVideoAttachment(attachments[0])}
+          playIconOverlay={isVideoAttachment(attachment1)}
           height={150}
           width={150}
           cropWidth={GAP}
-          url={getThumbnailUrl(attachments[0])}
+          url={getThumbnailUrl(attachment1)}
           showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
           showVisualAttachment={showAttachmentOrNoLongerAvailableToast(0)}
           cancelDownload={cancelDownload}
@@ -258,19 +265,19 @@ export function ImageGrid({
           onError={onError}
         />
         <Image
-          alt={getAlt(attachments[1], i18n)}
+          alt={getAlt(attachment2, i18n)}
           i18n={i18n}
           theme={theme}
-          blurHash={attachments[1].blurHash}
+          blurHash={attachment2.blurHash}
           bottomOverlay={withBottomOverlay}
           noBorder={false}
           curveTopRight={curveTopRight}
           curveBottomRight={curveBottomRight}
-          playIconOverlay={isVideoAttachment(attachments[1])}
+          playIconOverlay={isVideoAttachment(attachment2)}
           height={150}
           width={150}
-          attachment={attachments[1]}
-          url={getThumbnailUrl(attachments[1])}
+          attachment={attachment2}
+          url={getThumbnailUrl(attachment2)}
           showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
           showVisualAttachment={showAttachmentOrNoLongerAvailableToast(1)}
           cancelDownload={cancelDownload}
@@ -284,23 +291,27 @@ export function ImageGrid({
   }
 
   if (attachments.length === 3) {
+    const [attachment1, attachment2, attachment3] = attachments;
+    strictAssert(attachment1, 'Missing attachment 1');
+    strictAssert(attachment2, 'Missing attachment 2');
+    strictAssert(attachment3, 'Missing attachment 3');
     return (
       <div className="module-image-grid">
         <Image
-          alt={getAlt(attachments[0], i18n)}
+          alt={getAlt(attachment1, i18n)}
           i18n={i18n}
           theme={theme}
-          blurHash={attachments[0].blurHash}
+          blurHash={attachment1.blurHash}
           bottomOverlay={withBottomOverlay}
           noBorder={false}
           curveTopLeft={curveTopLeft}
           curveBottomLeft={curveBottomLeft}
-          attachment={attachments[0]}
-          playIconOverlay={isVideoAttachment(attachments[0])}
+          attachment={attachment1}
+          playIconOverlay={isVideoAttachment(attachment1)}
           height={200}
           width={200}
           cropWidth={GAP}
-          url={getUrl(attachments[0])}
+          url={getUrl(attachment1)}
           showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
           showVisualAttachment={showAttachmentOrNoLongerAvailableToast(0)}
           cancelDownload={cancelDownload}
@@ -309,17 +320,17 @@ export function ImageGrid({
         />
         <div className="module-image-grid__column">
           <Image
-            alt={getAlt(attachments[1], i18n)}
+            alt={getAlt(attachment2, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[1].blurHash}
+            blurHash={attachment2.blurHash}
             curveTopRight={curveTopRight}
             height={100}
             width={100}
             cropHeight={GAP}
-            attachment={attachments[1]}
-            playIconOverlay={isVideoAttachment(attachments[1])}
-            url={getThumbnailUrl(attachments[1])}
+            attachment={attachment2}
+            playIconOverlay={isVideoAttachment(attachment2)}
+            url={getThumbnailUrl(attachment2)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showAttachmentOrNoLongerAvailableToast(1)}
             cancelDownload={cancelDownload}
@@ -327,18 +338,18 @@ export function ImageGrid({
             onError={onError}
           />
           <Image
-            alt={getAlt(attachments[2], i18n)}
+            alt={getAlt(attachment3, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[2].blurHash}
+            blurHash={attachment3.blurHash}
             bottomOverlay={withBottomOverlay}
             noBorder={false}
             curveBottomRight={curveBottomRight}
             height={100}
             width={100}
-            attachment={attachments[2]}
-            playIconOverlay={isVideoAttachment(attachments[2])}
-            url={getThumbnailUrl(attachments[2])}
+            attachment={attachment3}
+            playIconOverlay={isVideoAttachment(attachment3)}
+            url={getThumbnailUrl(attachment3)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showAttachmentOrNoLongerAvailableToast(2)}
             cancelDownload={cancelDownload}
@@ -353,24 +364,29 @@ export function ImageGrid({
   }
 
   if (attachments.length === 4) {
+    const [attachment1, attachment2, attachment3, attachment4] = attachments;
+    strictAssert(attachment1, 'Missing attachment 1');
+    strictAssert(attachment2, 'Missing attachment 2');
+    strictAssert(attachment3, 'Missing attachment 3');
+    strictAssert(attachment4, 'Missing attachment 4');
     return (
       <div className="module-image-grid">
         <div className="module-image-grid__column">
           <div className="module-image-grid__row">
             <Image
-              alt={getAlt(attachments[0], i18n)}
+              alt={getAlt(attachment1, i18n)}
               i18n={i18n}
               theme={theme}
-              blurHash={attachments[0].blurHash}
+              blurHash={attachment1.blurHash}
               curveTopLeft={curveTopLeft}
               noBorder={false}
-              attachment={attachments[0]}
-              playIconOverlay={isVideoAttachment(attachments[0])}
+              attachment={attachment1}
+              playIconOverlay={isVideoAttachment(attachment1)}
               height={150}
               width={150}
               cropHeight={GAP}
               cropWidth={GAP}
-              url={getThumbnailUrl(attachments[0])}
+              url={getThumbnailUrl(attachment1)}
               showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
               showVisualAttachment={showAttachmentOrNoLongerAvailableToast(0)}
               cancelDownload={cancelDownload}
@@ -378,18 +394,18 @@ export function ImageGrid({
               onError={onError}
             />
             <Image
-              alt={getAlt(attachments[1], i18n)}
+              alt={getAlt(attachment2, i18n)}
               i18n={i18n}
               theme={theme}
-              blurHash={attachments[1].blurHash}
+              blurHash={attachment2.blurHash}
               curveTopRight={curveTopRight}
-              playIconOverlay={isVideoAttachment(attachments[1])}
+              playIconOverlay={isVideoAttachment(attachment2)}
               noBorder={false}
               height={150}
               width={150}
               cropHeight={GAP}
-              attachment={attachments[1]}
-              url={getThumbnailUrl(attachments[1])}
+              attachment={attachment2}
+              url={getThumbnailUrl(attachment2)}
               showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
               showVisualAttachment={showAttachmentOrNoLongerAvailableToast(1)}
               cancelDownload={cancelDownload}
@@ -399,19 +415,19 @@ export function ImageGrid({
           </div>
           <div className="module-image-grid__row">
             <Image
-              alt={getAlt(attachments[2], i18n)}
+              alt={getAlt(attachment3, i18n)}
               i18n={i18n}
               theme={theme}
-              blurHash={attachments[2].blurHash}
+              blurHash={attachment3.blurHash}
               bottomOverlay={withBottomOverlay}
               noBorder={false}
               curveBottomLeft={curveBottomLeft}
-              playIconOverlay={isVideoAttachment(attachments[2])}
+              playIconOverlay={isVideoAttachment(attachment3)}
               height={150}
               width={150}
               cropWidth={GAP}
-              attachment={attachments[2]}
-              url={getThumbnailUrl(attachments[2])}
+              attachment={attachment3}
+              url={getThumbnailUrl(attachment3)}
               showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
               showVisualAttachment={showAttachmentOrNoLongerAvailableToast(2)}
               cancelDownload={cancelDownload}
@@ -419,18 +435,18 @@ export function ImageGrid({
               onError={onError}
             />
             <Image
-              alt={getAlt(attachments[3], i18n)}
+              alt={getAlt(attachment4, i18n)}
               i18n={i18n}
               theme={theme}
-              blurHash={attachments[3].blurHash}
+              blurHash={attachment4.blurHash}
               bottomOverlay={withBottomOverlay}
               noBorder={false}
               curveBottomRight={curveBottomRight}
-              playIconOverlay={isVideoAttachment(attachments[3])}
+              playIconOverlay={isVideoAttachment(attachment4)}
               height={150}
               width={150}
-              attachment={attachments[3]}
-              url={getThumbnailUrl(attachments[3])}
+              attachment={attachment4}
+              url={getThumbnailUrl(attachment4)}
               showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
               showVisualAttachment={showAttachmentOrNoLongerAvailableToast(3)}
               cancelDownload={cancelDownload}
@@ -450,22 +466,30 @@ export function ImageGrid({
     ? `+${attachments.length - 5}`
     : undefined;
 
+  const [attachment1, attachment2, attachment3, attachment4, attachment5] =
+    attachments;
+  strictAssert(attachment1, 'Missing attachment 1');
+  strictAssert(attachment2, 'Missing attachment 2');
+  strictAssert(attachment3, 'Missing attachment 3');
+  strictAssert(attachment4, 'Missing attachment 4');
+  strictAssert(attachment5, 'Missing attachment 4');
+
   return (
     <div className="module-image-grid">
       <div className="module-image-grid__column">
         <div className="module-image-grid__row">
           <Image
-            alt={getAlt(attachments[0], i18n)}
+            alt={getAlt(attachment1, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[0].blurHash}
+            blurHash={attachment1.blurHash}
             curveTopLeft={curveTopLeft}
-            attachment={attachments[0]}
-            playIconOverlay={isVideoAttachment(attachments[0])}
+            attachment={attachment1}
+            playIconOverlay={isVideoAttachment(attachment1)}
             height={150}
             width={150}
             cropWidth={GAP}
-            url={getThumbnailUrl(attachments[0])}
+            url={getThumbnailUrl(attachment1)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showVisualAttachment}
             cancelDownload={cancelDownload}
@@ -473,16 +497,16 @@ export function ImageGrid({
             onError={onError}
           />
           <Image
-            alt={getAlt(attachments[1], i18n)}
+            alt={getAlt(attachment2, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[1].blurHash}
+            blurHash={attachment2.blurHash}
             curveTopRight={curveTopRight}
-            playIconOverlay={isVideoAttachment(attachments[1])}
+            playIconOverlay={isVideoAttachment(attachment2)}
             height={150}
             width={150}
-            attachment={attachments[1]}
-            url={getThumbnailUrl(attachments[1])}
+            attachment={attachment2}
+            url={getThumbnailUrl(attachment2)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showVisualAttachment}
             cancelDownload={cancelDownload}
@@ -492,19 +516,19 @@ export function ImageGrid({
         </div>
         <div className="module-image-grid__row">
           <Image
-            alt={getAlt(attachments[2], i18n)}
+            alt={getAlt(attachment3, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[2].blurHash}
+            blurHash={attachment3.blurHash}
             bottomOverlay={withBottomOverlay}
             noBorder={isSticker}
             curveBottomLeft={curveBottomLeft}
-            playIconOverlay={isVideoAttachment(attachments[2])}
+            playIconOverlay={isVideoAttachment(attachment3)}
             height={100}
             width={100}
             cropWidth={GAP}
-            attachment={attachments[2]}
-            url={getThumbnailUrl(attachments[2])}
+            attachment={attachment3}
+            url={getThumbnailUrl(attachment3)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showVisualAttachment}
             cancelDownload={cancelDownload}
@@ -512,18 +536,18 @@ export function ImageGrid({
             onError={onError}
           />
           <Image
-            alt={getAlt(attachments[3], i18n)}
+            alt={getAlt(attachment4, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[3].blurHash}
+            blurHash={attachment4.blurHash}
             bottomOverlay={withBottomOverlay}
             noBorder={isSticker}
-            playIconOverlay={isVideoAttachment(attachments[3])}
+            playIconOverlay={isVideoAttachment(attachment4)}
             height={100}
             width={100}
             cropWidth={GAP}
-            attachment={attachments[3]}
-            url={getThumbnailUrl(attachments[3])}
+            attachment={attachment4}
+            url={getThumbnailUrl(attachment4)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showVisualAttachment}
             cancelDownload={cancelDownload}
@@ -531,20 +555,20 @@ export function ImageGrid({
             onError={onError}
           />
           <Image
-            alt={getAlt(attachments[4], i18n)}
+            alt={getAlt(attachment5, i18n)}
             i18n={i18n}
             theme={theme}
-            blurHash={attachments[4].blurHash}
+            blurHash={attachment5.blurHash}
             bottomOverlay={withBottomOverlay}
             noBorder={isSticker}
             curveBottomRight={curveBottomRight}
-            playIconOverlay={isVideoAttachment(attachments[4])}
+            playIconOverlay={isVideoAttachment(attachment5)}
             height={100}
             width={100}
             darkOverlay={moreMessagesOverlay}
             overlayText={moreMessagesOverlayText}
-            attachment={attachments[4]}
-            url={getThumbnailUrl(attachments[4])}
+            attachment={attachment5}
+            url={getThumbnailUrl(attachment5)}
             showMediaNoLongerAvailableToast={showMediaNoLongerAvailableToast}
             showVisualAttachment={showVisualAttachment}
             cancelDownload={undefined}

ts/components/conversation/Message.dom.tsx

@@ -108,7 +108,7 @@ import { getColorForCallLink } from '../../util/getColorForCallLink.std.js';
 import { getKeyFromCallLink } from '../../util/callLinks.std.js';
 import { InAnotherCallTooltip } from './InAnotherCallTooltip.dom.js';
 import { formatFileSize } from '../../util/formatFileSize.std.js';
-import { assertDev } from '../../util/assert.std.js';
+import { assertDev, strictAssert } from '../../util/assert.std.js';
 import { AttachmentStatusIcon } from './AttachmentStatusIcon.dom.js';
 import { TapToViewNotAvailableType } from '../TapToViewNotAvailableModal.dom.js';
 import type { DataPropsType as TapToViewNotAvailablePropsType } from '../TapToViewNotAvailableModal.dom.js';
@@ -491,17 +491,19 @@ const MessageReactions = forwardRef(function MessageReactions(
   const reactionsContainerRefMerger = useRef(createRefMerger());
 
   // Take the first three groups for rendering
-  const toRender = take(ordered, 3).map(res => {
-    const isMe = res.some(re => Boolean(re.from.isMe));
-    const count = res.length;
-    const { emoji } = res[0];
+  const toRender = take(ordered, 3).map(group => {
+    const isMe = group.some(re => Boolean(re.from.isMe));
+    const count = group.length;
+    const firstReaction = group[0];
+    strictAssert(firstReaction, 'Missing firstReaction');
+    const { emoji } = firstReaction;
 
     let label: string;
     if (isMe) {
       label = i18n('icu:Message__reaction-emoji-label--you', { emoji });
     } else if (count === 1) {
       label = i18n('icu:Message__reaction-emoji-label--single', {
-        title: res[0].from.title,
+        title: firstReaction.from.title,
         emoji,
       });
     } else {
@@ -2543,6 +2545,7 @@ export class Message extends React.PureComponent<Props, State> {
     }
 
     const onlyPreview = previews[0];
+    strictAssert(onlyPreview, 'Missing onlyPreview');
     return Boolean(onlyPreview.isCallLink);
   }
 
@@ -2551,6 +2554,7 @@ export class Message extends React.PureComponent<Props, State> {
 
     if (this.#shouldShowJoinButton()) {
       const firstPreview = previews[0];
+      strictAssert(firstPreview, 'Missing firstPreview');
       const inAnotherCall = Boolean(
         activeCallConversationId &&
         (!firstPreview.callLinkRoomId ||
@@ -2672,6 +2676,7 @@ export class Message extends React.PureComponent<Props, State> {
 
     if (previews && previews.length) {
       const first = previews[0];
+      strictAssert(first, 'Missing first');
       const { image } = first;
 
       return isImageAttachment(image);
@@ -2688,6 +2693,7 @@ export class Message extends React.PureComponent<Props, State> {
     }
 
     const first = attachments[0];
+    strictAssert(first, 'Missing first');
 
     return Boolean(first.pending);
   }
@@ -3216,6 +3222,7 @@ export class Message extends React.PureComponent<Props, State> {
       event.stopPropagation();
 
       const attachment = attachments[0];
+      strictAssert(attachment, 'Missing attachment');
 
       showLightbox({ attachment, messageId: id });
     }

ts/components/conversation/ReactionViewer.dom.tsx

@@ -168,6 +168,7 @@ export const ReactionViewer = React.forwardRef<HTMLDivElement, Props>(
               // Find the local user's reaction first, then fall back to most recent
               const localUserReaction = groupedReactions.find(r => r.from.isMe);
               const firstReaction = localUserReaction || groupedReactions[0];
+              strictAssert(firstReaction, 'Missing firstReaction');
               return {
                 id: firstReaction.parentKey,
                 index: DEFAULT_EMOJI_ORDER.includes(firstReaction.parentKey)

ts/components/conversation/Timeline.dom.tsx

@@ -260,6 +260,7 @@ export class Timeline extends React.Component<
     if (setFocus && items && items.length > 0) {
       const lastIndex = items.length - 1;
       const lastMessageId = items[lastIndex];
+      strictAssert(lastMessageId, 'Missing lastMessageId');
       targetMessage(lastMessageId, id);
     } else {
       const containerEl = this.#containerRef.current;
@@ -307,6 +308,7 @@ export class Timeline extends React.Component<
     ) {
       if (setFocus) {
         const messageId = items[oldestUnseenIndex];
+        strictAssert(messageId, 'Missing messageId');
         targetMessage(messageId, id);
       } else {
         this.#lastSeenIndicatorRef.current?.scrollIntoView();
@@ -824,6 +826,7 @@ export class Timeline extends React.Component<
       }
 
       const messageId = items[targetIndex];
+      strictAssert(messageId, 'Missing messageId');
       targetMessage(messageId, id);
 
       event.preventDefault();
@@ -851,6 +854,7 @@ export class Timeline extends React.Component<
       }
 
       const messageId = items[targetIndex];
+      strictAssert(messageId, 'Missing messageId');
       targetMessage(messageId, id);
 
       event.preventDefault();

ts/components/conversation/TimelineMessage.dom.stories.tsx

@@ -3424,7 +3424,8 @@ export const EmbeddedContactWithSendMessage = Template.bind({});
 EmbeddedContactWithSendMessage.args = {
   contact: {
     ...fullContact,
-    firstNumber: fullContact.number[0].value,
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    firstNumber: fullContact.number[0]!.value,
     serviceId: generateAci(),
   },
   direction: 'incoming',

ts/components/conversation/TimelineMessage.dom.tsx

@@ -250,7 +250,8 @@ export function TimelineMessage(props: Props): React.JSX.Element {
       if (attachments.length !== 1) {
         saveAttachments(attachments, timestamp);
       } else {
-        saveAttachment(attachments[0], timestamp);
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        saveAttachment(attachments[0]!, timestamp);
       }
     },
     [

ts/components/conversation/TypingBubble.dom.tsx

@@ -341,8 +341,10 @@ export function TypingBubble({
       return;
     }
 
-    const lastTypingContactId = typingContactIds[0];
-    const lastTypingTimestamp = typingContactIdTimestamps[lastTypingContactId];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const lastTypingContactId = typingContactIds[0]!;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const lastTypingTimestamp = typingContactIdTimestamps[lastTypingContactId]!;
     if (
       lastItemAuthorId === lastTypingContactId &&
       lastItemTimestamp > lastTypingTimestamp

ts/components/conversation/conversation-details/AddGroupMembersModal/ChooseGroupMembersModal.dom.tsx

@@ -216,6 +216,7 @@ export function ChooseGroupMembersModal({
 
     if (virtualIndex < filteredContacts.length) {
       const contact = filteredContacts[virtualIndex];
+      strictAssert(contact, 'Missing contact');
 
       const isSelected = selectedConversationIdsSet.has(contact.id);
       const isAlreadyInGroup = conversationIdsAlreadyInGroup.has(contact.id);

ts/components/conversation/conversation-details/ConversationDetails.dom.stories.tsx

@@ -18,6 +18,7 @@ import { ThemeType } from '../../../types/Util.std.js';
 import { DurationInSeconds } from '../../../util/durations/index.std.js';
 import { NavTab } from '../../../types/Nav.std.js';
 import { getFakeCallHistoryGroup } from '../../../test-helpers/getFakeCallHistoryGroup.std.js';
+import type { ContactNameColorType } from '../../../types/Colors.std.js';
 import { ContactNameColors } from '../../../types/Colors.std.js';
 import { isNotNil } from '../../../util/isNotNil.std.js';
 
@@ -52,16 +53,20 @@ const createProps = (
       isMe: i === 2,
     }),
   }));
-  const memberColors = new Map<string, string>(
+  const memberColors = new Map<string, ContactNameColorType>(
     memberships
-      .map((membership, i): [string, string] | null => {
+      .map((membership, i): [string, ContactNameColorType] | null => {
         const { serviceId } = membership.member;
 
         if (!serviceId) {
           return null;
         }
 
-        return [serviceId.toString(), ContactNameColors[i]];
+        return [
+          serviceId.toString(),
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          ContactNameColors[i % ContactNameColors.length]!,
+        ];
       })
       .filter(isNotNil)
   );

ts/components/conversation/conversation-details/ConversationDetails.dom.tsx

@@ -68,6 +68,7 @@ import { BadgeSustainerInstructionsDialog } from '../../BadgeSustainerInstructio
 import type { ContactModalStateType } from '../../../types/globalModals.std.js';
 import type { ShowToastAction } from '../../../state/ducks/toast.preload.js';
 import { ToastType } from '../../../types/Toast.dom.js';
+import type { ContactNameColorType } from '../../../types/Colors.std.js';
 
 enum ModalState {
   AddingGroupMembers,
@@ -101,7 +102,7 @@ export type StateProps = {
   maxGroupSize: number;
   maxRecommendedGroupSize: number;
   memberships: ReadonlyArray<GroupV2Membership>;
-  memberColors: Map<string, string>;
+  memberColors: Map<string, ContactNameColorType>;
   pendingApprovalMemberships: ReadonlyArray<GroupV2RequestingMembership>;
   pendingAvatarDownload?: boolean;
   pendingMemberships: ReadonlyArray<GroupV2PendingMembership>;

ts/components/conversation/conversation-details/ConversationDetailsMembershipList.dom.stories.tsx

@@ -12,6 +12,7 @@ import type {
   GroupV2Membership,
 } from './ConversationDetailsMembershipList.dom.js';
 import { ConversationDetailsMembershipList } from './ConversationDetailsMembershipList.dom.js';
+import type { ContactNameColorType } from '../../../types/Colors.std.js';
 import { ContactNameColors } from '../../../types/Colors.std.js';
 
 const { i18n } = window.SignalContext;
@@ -33,11 +34,12 @@ const createMemberships = (
 
 const getMemberColors = (
   memberships: Array<GroupV2Membership>
-): Map<string, string> =>
+): Map<string, ContactNameColorType> =>
   new Map(
     memberships.map((membership, i) => [
       membership.member.id,
-      ContactNameColors[i],
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      ContactNameColors[i % ContactNameColors.length]!,
     ])
   );
 

ts/components/conversation/conversation-details/ConversationDetailsMembershipList.dom.tsx

@@ -19,6 +19,7 @@ import { PanelSection } from './PanelSection.dom.js';
 import { GroupMemberLabel } from '../ContactName.dom.js';
 import { AriaClickable } from '../../../axo/AriaClickable.dom.js';
 import type { ContactModalStateType } from '../../../types/globalModals.std.js';
+import type { ContactNameColorType } from '../../../types/Colors.std.js';
 
 export type GroupV2Membership = {
   isAdmin: boolean;
@@ -36,7 +37,7 @@ export type Props = {
   isEditMemberLabelEnabled: boolean;
   maxShownMemberCount?: number;
   memberships: ReadonlyArray<GroupV2Membership>;
-  memberColors: Map<string, string>;
+  memberColors: Map<string, ContactNameColorType>;
   showContactModal: (payload: ContactModalStateType) => void;
   showLabelEditor: () => void;
   startAddingNewMembers?: () => void;

ts/components/conversation/conversation-details/GroupMemberLabelEditor.dom.tsx

@@ -23,6 +23,7 @@ import {
   MessageInteractivity,
   TextDirection,
 } from '../Message.dom.js';
+import type { ContactNameColorType } from '../../../types/Colors.std.js';
 import { ConversationColors } from '../../../types/Colors.std.js';
 import { WidthBreakpoint } from '../../_util.std.js';
 import { AxoAlertDialog } from '../../../axo/AxoAlertDialog.dom.js';
@@ -52,13 +53,13 @@ export type PropsDataType = {
   isActive: boolean;
   me: ConversationType;
   membersWithLabel: Array<{
-    contactNameColor: string;
+    contactNameColor: ContactNameColorType;
     isAdmin: boolean;
     labelEmoji: string | undefined;
     labelString: string;
     member: ConversationType;
   }>;
-  ourColor: string | undefined;
+  ourColor: ContactNameColorType | undefined;
   theme: ThemeType;
 };
 

ts/components/conversation/conversation-details/PendingInvites.dom.tsx

@@ -18,7 +18,6 @@ import {
 } from './ConversationDetailsIcon.dom.js';
 import { isAccessControlEnabled } from '../../../groups/util.std.js';
 import { Tabs } from '../../Tabs.dom.js';
-import { assertDev } from '../../../util/assert.std.js';
 
 export type PropsDataType = {
   readonly conversation?: ConversationType;
@@ -197,11 +196,13 @@ function MembershipActionConfirmation({
     }
     approvePendingMembershipFromGroupV2(
       conversation.id,
-      stagedMemberships[0].membership.member.id
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      stagedMemberships[0]!.membership.member.id
     );
   };
 
-  const membershipType = stagedMemberships[0].type;
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  const membershipType = stagedMemberships[0]!.type;
 
   const modalAction =
     membershipType === StageType.APPROVE_REQUEST
@@ -255,12 +256,13 @@ function getConfirmationMessage({
   ourAci: AciString;
   stagedMemberships: ReadonlyArray<StagedMembershipType>;
 }>): string {
-  if (!stagedMemberships || !stagedMemberships.length) {
+  const [stagedMembership] = stagedMemberships;
+  if (stagedMembership == null) {
     return '';
   }
 
-  const membershipType = stagedMemberships[0].type;
-  const firstMembership = stagedMemberships[0].membership;
+  const membershipType = stagedMembership.type;
+  const firstMembership = stagedMembership.membership;
 
   // Requesting a membership since they weren't added by anyone
   if (membershipType === StageType.DENY_REQUEST) {
@@ -419,19 +421,23 @@ function MembersPendingProfileKey({
   const { [ourAci]: ourPendingMemberships, ...otherPendingMembershipGroups } =
     groupedPendingMemberships;
 
-  const otherPendingMemberships = Object.keys(otherPendingMembershipGroups)
-    .map(id => members.find(member => member.serviceId === id))
-    .filter((member): member is ConversationType => member !== undefined)
-    .map(member => {
-      assertDev(
-        member.serviceId,
-        'We just verified that member has serviceId above'
-      );
-      return {
-        member,
-        pendingMemberships: otherPendingMembershipGroups[member.serviceId],
-      };
+  const otherPendingMemberships: Array<{
+    member: ConversationType;
+    pendingMemberships: Array<GroupV2PendingMembership>;
+  }> = [];
+
+  for (const [id, pendingMemberships] of Object.entries(
+    otherPendingMembershipGroups
+  )) {
+    const member = members.find(m => m.serviceId === id);
+    if (member == null) {
+      continue;
+    }
+    otherPendingMemberships.push({
+      member,
+      pendingMemberships,
     });
+  }
 
   return (
     <PanelSection>

ts/components/conversation/conversation-details/util.std.ts

@@ -15,19 +15,15 @@ export const bemGenerator =
     const base = `${block}__${element}`;
     const classes = [base];
 
-    let conditionals: Record<string, boolean> = {};
+    const conditionals: Record<string, boolean> = {};
 
     if (modifier) {
       if (typeof modifier === 'string') {
         classes.push(`${base}--${modifier}`);
       } else {
-        conditionals = Object.keys(modifier).reduce(
-          (acc, key) => ({
-            ...acc,
-            [`${base}--${key}`]: modifier[key],
-          }),
-          {} as Record<string, boolean>
-        );
+        for (const [key, value] of Object.entries(modifier)) {
+          conditionals[`${base}--${key}`] = value;
+        }
       }
     }
 

ts/components/conversation/media-gallery/MediaGallery.dom.tsx

@@ -180,7 +180,8 @@ function MediaSection({
 
   const sections = groupedItems.map((section, index) => {
     const isLast = index === groupedItems.length - 1;
-    const first = section.mediaItems[0];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const first = section.mediaItems[0]!;
     const { message } = first;
     const date = moment(message.receivedAtMs || message.receivedAt);
 

ts/components/conversation/media-gallery/utils/mocks.std.ts

@@ -2,7 +2,7 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import lodash from 'lodash';
-import { type MIMEType, IMAGE_JPEG } from '../../../../types/MIME.std.js';
+import { IMAGE_JPEG, stringToMIMEType } from '../../../../types/MIME.std.js';
 import type {
   MediaItemType,
   ContactMediaItemType,
@@ -21,17 +21,22 @@ export const days = (n: number): number => n * DAY_MS;
 const tokens = ['foo', 'bar', 'baz', 'qux', 'quux'];
 
 const contentTypes = {
-  gif: 'image/gif',
-  jpg: 'image/jpeg',
-  png: 'image/png',
-  mp4: 'video/mp4',
-  docx: 'application/text',
-  pdf: 'application/pdf',
-  exe: 'application/exe',
-  txt: 'application/text',
-} as unknown as Record<string, MIMEType>;
+  gif: stringToMIMEType('image/gif'),
+  jpg: stringToMIMEType('image/jpeg'),
+  png: stringToMIMEType('image/png'),
+  mp3: stringToMIMEType('audio/mp3'),
+  mp4: stringToMIMEType('video/mp4'),
+  docx: stringToMIMEType('application/text'),
+  pdf: stringToMIMEType('application/pdf'),
+  exe: stringToMIMEType('application/exe'),
+  txt: stringToMIMEType('application/text'),
+} as const;
 
-function createRandomAttachment(fileExtension: string): AttachmentForUIType {
+type FileExtension = keyof typeof contentTypes;
+
+function createRandomAttachment(
+  fileExtension: FileExtension
+): AttachmentForUIType {
   const contentType = contentTypes[fileExtension];
   const fileName = `${sample(tokens)}${sample(tokens)}.${fileExtension}`;
 
@@ -101,7 +106,7 @@ function createRandomFile(
   type: 'media' | 'document' | 'audio',
   startTime: number,
   timeWindow: number,
-  fileExtension: string
+  fileExtension: FileExtension
 ): MediaItemType {
   return {
     type,
@@ -154,15 +159,11 @@ function createRandomFiles(
   type: 'media' | 'document' | 'audio',
   startTime: number,
   timeWindow: number,
-  fileExtensions: Array<string>
+  fileExtensions: Array<FileExtension>
 ): Array<MediaItemType> {
   return range(random(5, 20)).map(() =>
-    createRandomFile(
-      type,
-      startTime,
-      timeWindow,
-      sample(fileExtensions) as string
-    )
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    createRandomFile(type, startTime, timeWindow, sample(fileExtensions)!)
   );
 }
 export function createRandomDocuments(

ts/components/conversation/pinned-messages/PinnedMessagesBar.dom.tsx

@@ -105,8 +105,7 @@ export const PinnedMessagesBar = memo(function PinnedMessagesBar(
       return null;
     }
 
-    for (let index = 0; index < pins.length; index += 1) {
-      const value = pins[index];
+    for (const [index, value] of pins.entries()) {
       if (value.id === current) {
         return { index, value };
       }

ts/components/fun/FunEmoji.dom.stories.tsx

@@ -77,7 +77,8 @@ export function All(props: AllProps): React.JSX.Element {
         }}
       >
         {rowVirtualizer.getVirtualItems().map(rowItem => {
-          const row = rows[rowItem.index];
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          const row = rows[rowItem.index]!;
           return (
             <div
               key={rowItem.index}

ts/components/fun/panels/FunPanelGifs.dom.tsx

@@ -319,6 +319,7 @@ export function FunPanelGifs({
   const estimateSize = useCallback(
     (index: number) => {
       const gif = items[index];
+      strictAssert(gif, 'Missing gif');
       const aspectRatio = gif.previewMedia.width / gif.previewMedia.height;
       const baseHeight = GIF_WATERFALL_ITEM_WIDTH / aspectRatio;
       return baseHeight + GIF_WATERFALL_ITEM_MARGIN + GIF_WATERFALL_ITEM_MARGIN;
@@ -350,7 +351,8 @@ export function FunPanelGifs({
 
   const getItemKey = useCallback(
     (index: number) => {
-      return items[index].id;
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return items[index]!.id;
     },
     [items]
   );
@@ -578,6 +580,7 @@ export function FunPanelGifs({
                 <FunWaterfallContainer totalSize={virtualizer.getTotalSize()}>
                   {virtualizer.getVirtualItems().map(item => {
                     const gif = items[item.index];
+                    strictAssert(gif, 'Missing gif');
                     const key = String(item.key);
                     const isTabbable =
                       selectedItemKey != null

ts/components/fun/panels/FunPanelStickers.dom.tsx

@@ -605,6 +605,7 @@ const Cell = memo(function Cell(props: {
 }): React.JSX.Element {
   const { onClickSticker, onClickTimeSticker } = props;
   const stickerLookupItem = props.stickerLookup[props.value];
+  strictAssert(stickerLookupItem, 'Missing stickerLookupItem');
 
   const handleClick = useCallback(
     (event: PointerEvent) => {

ts/components/fun/virtual/useFunVirtualGrid.dom.tsx

@@ -207,11 +207,15 @@ function buildLayout(
   totalHeight: number
 ): Layout {
   const groups = groupBy(virtualItems, virtualItem => {
-    return list.listItems[virtualItem.index].sectionMeta.sectionKey;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    return list.listItems[virtualItem.index]!.sectionMeta.sectionKey;
   });
 
   const sections = Object.keys(groups).map((sectionKey): SectionLayoutNode => {
-    const [headerVirtualItem, ...rowVirtualItems] = groups[sectionKey];
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const [maybeHeaderVirtualItem, ...rowVirtualItems] = groups[sectionKey]!;
+    // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+    const headerVirtualItem = maybeHeaderVirtualItem!;
     const headerListItem = list.listItems.at(headerVirtualItem.index);
 
     strictAssert(
@@ -446,7 +450,8 @@ export function useFunVirtualGrid({
 
   const getItemKey = useCallback(
     (index: number) => {
-      return list.listItems[index].key;
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      return list.listItems[index]!.key;
     },
     [list]
   );

ts/components/leftPane/LeftPaneChooseGroupMembersHelper.dom.tsx

@@ -315,7 +315,8 @@ export class LeftPaneChooseGroupMembersHelper extends LeftPaneHelper<LeftPaneCho
       }
 
       if (virtualRowIndex <= this.#candidateContacts.length) {
-        const contact = this.#candidateContacts[virtualRowIndex - 1];
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        const contact = this.#candidateContacts[virtualRowIndex - 1]!;
 
         const isChecked = this.#selectedConversationIdsSet.has(contact.id);
         const disabledReason =

ts/components/leftPane/LeftPaneInboxHelper.dom.tsx

@@ -239,7 +239,8 @@ export class LeftPaneInboxHelper extends LeftPaneHelper<LeftPaneInboxPropsType>
       if (index < pinnedConversations.length) {
         return {
           type: RowType.Conversation,
-          conversation: pinnedConversations[index],
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          conversation: pinnedConversations[index]!,
         };
       }
       index -= pinnedConversations.length;
@@ -259,7 +260,8 @@ export class LeftPaneInboxHelper extends LeftPaneHelper<LeftPaneInboxPropsType>
     if (index < conversations.length) {
       return {
         type: RowType.Conversation,
-        conversation: conversations[index],
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        conversation: conversations[index]!,
       };
     }
     index -= conversations.length;

ts/components/leftPane/LeftPaneSearchHelper.dom.tsx

@@ -18,7 +18,7 @@ import type {
 import { LeftPaneSearchInput } from '../LeftPaneSearchInput.dom.js';
 
 import { I18n } from '../I18n.dom.js';
-import { assertDev } from '../../util/assert.std.js';
+import { assertDev, strictAssert } from '../../util/assert.std.js';
 import { UserText } from '../UserText.dom.js';
 
 // The "correct" thing to do is to measure the size of the left pane and render enough
@@ -381,6 +381,7 @@ export class LeftPaneSearchHelper extends LeftPaneHelper<LeftPaneSearchPropsType
       }
       if (pointer < list.results.length) {
         const result = list.results[pointer];
+        strictAssert(result, 'Missing result');
         return result.type === 'incoming' || result.type === 'outgoing' // message
           ? {
               conversationId: result.conversationId,

ts/groups.preload.ts

@@ -3356,6 +3356,10 @@ export function _mergeGroupChangeMessages(
 
   const [firstDetail] = firstChange.details;
   const [secondDetail] = secondChange.details;
+
+  strictAssert(firstDetail, 'Missing firstDetail');
+  strictAssert(secondDetail, 'Missing secondDetail');
+
   let isApprovalPending: boolean;
   if (secondDetail.type === 'admin-approval-add-one') {
     isApprovalPending = true;
@@ -3428,6 +3432,7 @@ export function _isGroupChangeMessageBounceable(
   }
 
   const [first] = groupV2Change.details;
+  strictAssert(first, 'Missing first');
   if (
     first.type === 'admin-approval-add-one' ||
     first.type === 'admin-approval-bounce'
@@ -4267,18 +4272,14 @@ async function integrateGroupChanges({
   const finalMessages: Array<Array<GroupChangeMessageType>> = [];
   const finalNewProfileKeys = new Map<AciString, string>();
 
-  const imax = changes.length;
-  for (let i = 0; i < imax; i += 1) {
-    const { groupChanges } = changes[i];
+  for (const change of changes) {
+    const { groupChanges } = change;
 
     if (!groupChanges) {
       continue;
     }
 
-    const jmax = groupChanges.length;
-    for (let j = 0; j < jmax; j += 1) {
-      const changeState = groupChanges[j];
-
+    for (const changeState of groupChanges) {
       const { groupChange, groupState } = changeState;
 
       if (!groupChange && !groupState) {
@@ -4323,8 +4324,8 @@ async function integrateGroupChanges({
   if (isFirstFetch && moreThanOneVersion) {
     // The first array in finalMessages is from the first revision we could process. It
     //   should contain a message about how we joined the group.
-    const joinMessages = finalMessages[0];
-    const alreadyHaveJoinMessage = joinMessages && joinMessages.length > 0;
+    const joinMessage = finalMessages[0]?.[0];
+    const alreadyHaveJoinMessage = joinMessage != null;
 
     // There have been other changes since that first revision, so we generate diffs for
     //   the whole of the change since then, likely without the initial join message.
@@ -4334,9 +4335,8 @@ async function integrateGroupChanges({
       dropInitialJoinMessage: alreadyHaveJoinMessage,
     });
 
-    const groupChangeMessages = alreadyHaveJoinMessage
-      ? [joinMessages[0], ...otherMessages]
-      : otherMessages;
+    const groupChangeMessages =
+      joinMessage != null ? [joinMessage, ...otherMessages] : otherMessages;
 
     return {
       newAttributes: attributes,
@@ -4897,6 +4897,7 @@ function extractDiffs({
   const removedPendingMemberIds = Array.from(oldPendingMemberLookup.keys());
   if (removedPendingMemberIds.length > 1) {
     const firstUuid = removedPendingMemberIds[0];
+    strictAssert(firstUuid, 'Missing firstUuid');
     const firstRemovedMember = oldPendingMemberLookup.get(firstUuid);
     strictAssert(
       firstRemovedMember !== undefined,
@@ -4913,6 +4914,7 @@ function extractDiffs({
     });
   } else if (removedPendingMemberIds.length === 1) {
     const serviceId = removedPendingMemberIds[0];
+    strictAssert(serviceId, 'Missing serviceId');
     const removedMember = oldPendingMemberLookup.get(serviceId);
     strictAssert(removedMember !== undefined, 'Removed member not found');
 
@@ -5434,7 +5436,7 @@ async function applyGroupChange({
       members[aci] = {
         aci,
         joinedAtVersion: version,
-        role: previousRecord.role || MemberRole.DEFAULT,
+        role: previousRecord?.role || MemberRole.DEFAULT,
       };
 
       newProfileKeys.push({
@@ -5478,7 +5480,7 @@ async function applyGroupChange({
       members[aci] = {
         aci,
         joinedAtVersion: version,
-        role: previousRecord.role || MemberRole.DEFAULT,
+        role: previousRecord?.role || MemberRole.DEFAULT,
       };
 
       newProfileKeys.push({

ts/hooks/useRestoreFocus.dom.ts

@@ -6,7 +6,7 @@ import * as React from 'react';
 type CallbackType = (toFocus: HTMLElement | null | undefined) => void;
 
 // Restore focus on teardown
-export const useRestoreFocus = (): Array<CallbackType> => {
+export const useRestoreFocus = (): [CallbackType] => {
   const toFocusRef = React.useRef<HTMLElement | null>(null);
   const lastFocusedRef = React.useRef<HTMLElement | null>(null);
 

ts/hooks/useSizeObserver.dom.tsx

@@ -52,7 +52,8 @@ export function useSizeObserver<T extends Element = Element>(
       // We're only ever observing one element, and `ResizeObserver` for some
       // reason is an array of exactly one rect (I assume to support wrapped
       // inline elements in the future)
-      const borderBoxSize = entries[0].borderBoxSize[0];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const borderBoxSize = entries[0]!.borderBoxSize[0]!;
       // We are assuming a horizontal writing-mode here, we could call
       // `getBoundingClientRect()` here but MDN says not to. In the future if
       // we are adding support for a vertical locale we may need to change this

ts/hooks/useTabs.dom.tsx

@@ -52,7 +52,8 @@ export function useTabs(options: TabsOptionsType): TabsProps {
     // This is enforced by the type system.
     // eslint-disable-next-line react-hooks/rules-of-hooks
     const [tabState, setTabState] = useState<string>(
-      options.initialSelectedTab || options.tabs[0].id
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      options.initialSelectedTab || options.tabs[0]!.id
     );
 
     selectedTab = tabState;

ts/jobs/AttachmentBackupManager.preload.ts

@@ -604,6 +604,7 @@ async function copyToBackupTier({
   });
 
   const response = responses[0];
+  strictAssert(response, 'Missing response');
   if (!response.isSuccess) {
     if (response.status === FILE_NOT_FOUND_ON_TRANSIT_TIER_STATUS) {
       throw new FileNotFoundOnTransitTierError();

ts/jobs/conversationJobQueue.preload.ts

@@ -615,7 +615,8 @@ export class ConversationJobQueue extends JobQueue<ConversationQueueJobData> {
   #getRetryWithBackoff(attempts: number) {
     return (
       Date.now() +
-      MINUTE * (FIBONACCI[attempts] ?? FIBONACCI[FIBONACCI.length - 1])
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      MINUTE * (FIBONACCI[attempts] ?? FIBONACCI[FIBONACCI.length - 1]!)
     );
   }
 

ts/jobs/helpers/sendNormalMessage.preload.ts

@@ -392,7 +392,8 @@ export async function sendNormalMessage(
 
         log.info('sending direct message');
         innerPromise = messaging.sendMessageToServiceId({
-          serviceId: recipientServiceIdsWithoutMe[0],
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          serviceId: recipientServiceIdsWithoutMe[0]!,
           messageOptions: {
             attachments,
             body,
@@ -951,7 +952,8 @@ async function uploadMessageQuote({
       );
 
       const attachmentAfterThumbnailUpload =
-        attachmentsAfterThumbnailUpload[index];
+        // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+        attachmentsAfterThumbnailUpload[index]!;
       return {
         ...attachment,
         thumbnail: {

ts/jobs/helpers/sendPollTerminate.preload.ts

@@ -137,7 +137,8 @@ export async function sendPollTerminate(
         return;
       }
 
-      const recipientServiceId = recipients[0];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const recipientServiceId = recipients[0]!;
 
       jobLog.info(
         `${logId}: Sending direct poll terminate for poll timestamp ${targetTimestamp}`

ts/jobs/helpers/sendPollVote.preload.ts

@@ -242,7 +242,8 @@ export async function sendPollVote(
 
         promise = messaging.sendMessageProtoAndWait({
           timestamp: currentTimestamp,
-          recipients: [recipientServiceIdsWithoutMe[0]],
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          recipients: [recipientServiceIdsWithoutMe[0]!],
           proto: contentMessage,
           contentHint: ContentHint.Resendable,
           groupId: undefined,

ts/jobs/helpers/sendReaction.preload.ts

@@ -231,7 +231,8 @@ export async function sendReaction(
 
         log.info('sending direct reaction message');
         promise = messaging.sendMessageToServiceId({
-          serviceId: recipientServiceIdsWithoutMe[0],
+          // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+          serviceId: recipientServiceIdsWithoutMe[0]!,
           messageOptions: {
             reaction: reactionForSend,
             timestamp: pendingReaction.timestamp,

ts/jobs/helpers/sendStory.preload.ts

@@ -52,6 +52,7 @@ import {
   saveErrorsOnMessage,
 } from '../../test-node/util/messageFailures.preload.js';
 import { send } from '../../messages/send.preload.js';
+import { strictAssert } from '../../util/assert.std.js';
 
 const { isEqual } = lodash;
 
@@ -167,9 +168,9 @@ export async function sendStory(
           preview: undefined,
         };
       } else {
-        const hydratedPreview = (
-          await loadPreviewData([localAttachment.preview])
-        )[0];
+        const previewData = await loadPreviewData([localAttachment.preview]);
+        const hydratedPreview = previewData[0];
+        strictAssert(hydratedPreview, 'Missing hydratedPreview');
 
         textAttachment = {
           ...localAttachment,
@@ -495,57 +496,48 @@ export async function sendStory(
 
       let hasFailedSends = false;
 
-      const newSendStateByConversationId = Object.keys(
-        oldSendStateByConversationId
-      ).reduce((acc, conversationId) => {
-        const sendState = sentConversationIds.get(conversationId);
-        if (sendState) {
-          return {
-            ...acc,
-            [conversationId]: sendState,
-          };
-        }
+      const newSendStateByConversationId: SendStateByConversationId = {};
 
-        const oldSendState = {
-          ...oldSendStateByConversationId[conversationId],
-        };
-        if (!oldSendState) {
-          return acc;
+      for (const [conversationId, oldSendState] of Object.entries(
+        oldSendStateByConversationId
+      )) {
+        const sendState = sentConversationIds.get(conversationId);
+
+        if (sendState) {
+          newSendStateByConversationId[conversationId] = sendState;
+          continue;
         }
 
         const recipient = window.ConversationController.get(conversationId);
         if (!recipient) {
-          return acc;
+          continue;
         }
 
         if (isMe(recipient.attributes)) {
-          return acc;
+          continue;
         }
 
         if (recipient.isEverUnregistered()) {
           if (!isSent(oldSendState.status)) {
             // We should have filtered this out on initial send, but we'll drop them from
             //   send list here if needed.
-            return acc;
+            continue;
           }
 
           // If a previous send to them did succeed, we'll keep that status around
-          return {
-            ...acc,
-            [conversationId]: oldSendState,
-          };
+          newSendStateByConversationId[conversationId] = oldSendState;
         }
 
         hasFailedSends = true;
 
-        return {
-          ...acc,
-          [conversationId]: sendStateReducer(oldSendState, {
+        newSendStateByConversationId[conversationId] = sendStateReducer(
+          oldSendState,
+          {
             type: SendActionType.Failed,
             updatedAt: Date.now(),
-          }),
-        };
-      }, {} as SendStateByConversationId);
+          }
+        );
+      }
 
       if (hasFailedSends) {
         notifyStorySendFailed(message);
@@ -609,8 +601,9 @@ export async function sendStory(
       sendErrors.push(result);
     }
   });
-  if (sendErrors.length) {
-    throw sendErrors[0].reason;
+  const [firstError] = sendErrors;
+  if (firstError != null) {
+    throw firstError.reason;
   }
 }
 

ts/logging/log.std.ts

@@ -69,7 +69,8 @@ function getSubsystemColor(name: string): string {
   hash >>>= 0;
   /* eslint-enable no-bitwise */
 
-  const result = COLORS[hash % COLORS.length];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  const result = COLORS[hash % COLORS.length]!;
   SUBSYSTEM_COLORS.set(name, result);
 
   return result;

ts/logging/main_process_logging.main.ts

@@ -210,8 +210,10 @@ export function eliminateOutOfDateFiles(
             path: target,
             start: isLineAfterDate(start, date),
             end:
-              isLineAfterDate(end[end.length - 1], date) ||
-              isLineAfterDate(end[end.length - 2], date),
+              // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+              isLineAfterDate(end[end.length - 1]!, date) ||
+              // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+              isLineAfterDate(end[end.length - 2]!, date),
           };
 
           if (!file.start && !file.end) {

ts/messageModifiers/MessageReceipts.preload.ts

@@ -105,7 +105,8 @@ const processReceiptBatcher = createWaitBatcher({
         continue;
       }
       // All receipts have the same sentAt, so we can grab it from the first
-      const sentAt = receiptsForMessageSentAt[0].receiptSync.messageSentAt;
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const sentAt = receiptsForMessageSentAt[0]!.receiptSync.messageSentAt;
 
       const messagesMatchingTimestamp =
         // eslint-disable-next-line no-await-in-loop
@@ -374,7 +375,8 @@ function getTargetMessage({
     `);
   }
 
-  const message = matchingMessages[0];
+  // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+  const message = matchingMessages[0]!;
   return window.MessageCache.register(new MessageModel(message));
 }
 const wasDeliveredWithSealedSender = (

ts/messageModifiers/Polls.preload.ts

@@ -436,7 +436,8 @@ export async function handlePollVote(
     );
 
     if (existingVoteIndex !== -1) {
-      const existingVote = currentVotes[existingVoteIndex];
+      // eslint-disable-next-line @typescript-eslint/no-non-null-assertion
+      const existingVote = currentVotes[existingVoteIndex]!;
 
       if (newVote.voteCount > existingVote.voteCount) {
         updatedVotes = [...currentVotes];