Find by username: Don't automatically add .01 discriminator

_locales/en/messages.json

@@ -2866,7 +2866,11 @@
   },
   "icu:startConversation--username-not-found": {
     "messageformat": "{atUsername} is not a Signal user. Make sure you've entered the complete username.",
-    "description": "Shown in dialog if username is not found. Note that 'username' will be the output of at-username"
+    "description": "Shown in dialog if username is not found. Note that 'username' will be the output of at-username, no @ symbol"
+  },
+  "icu:startConversation--username-not-valid": {
+    "messageformat": "{atUsername} is not a valid username. Make sure you've entered the complete username followed by its set of digits.",
+    "description": "Shown in dialog if username is invalid. Note that 'username' will be the output of at-username, no @ symbol"
   },
   "icu:startConversation--phone-number-not-found": {
     "messageformat": "User not found. \"{phoneNumber}\" is not a Signal user.",

ts/components/GlobalModalContainer.dom.tsx

@@ -33,6 +33,7 @@ import {
 import type { SmartDraftGifMessageSendModalProps } from '../state/smart/DraftGifMessageSendModal.preload.js';
 import { CriticalIdlePrimaryDeviceModal } from './CriticalIdlePrimaryDeviceModal.dom.js';
 import { LowDiskSpaceBackupImportModal } from './LowDiskSpaceBackupImportModal.dom.js';
+import { isUsernameValid } from '../util/Username.dom.js';
 
 // NOTE: All types should be required for this component so that the smart
 // component gives you type errors when adding/removing props.
@@ -392,6 +393,13 @@ export function GlobalModalContainer({
       content = i18n('icu:startConversation--phone-number-not-found', {
         phoneNumber: userNotFoundModalState.phoneNumber,
       });
+    } else if (
+      userNotFoundModalState.type === 'username' &&
+      !isUsernameValid(userNotFoundModalState.username)
+    ) {
+      content = i18n('icu:startConversation--username-not-valid', {
+        atUsername: userNotFoundModalState.username,
+      });
     } else if (userNotFoundModalState.type === 'username') {
       content = i18n('icu:startConversation--username-not-found', {
         atUsername: userNotFoundModalState.username,

ts/test-electron/util/Username_test.dom.ts

@@ -6,27 +6,68 @@ import { assert } from 'chai';
 import * as Username from '../../util/Username.dom.js';
 
 describe('Username', () => {
+  describe('isUsernameValid', () => {
+    const { isUsernameValid } = Username;
+
+    it('returns false for missing discriminator', () => {
+      assert.isFalse(isUsernameValid('use'));
+      assert.isFalse(isUsernameValid('user'));
+      assert.isFalse(isUsernameValid('usern'));
+      assert.isFalse(isUsernameValid('usern.'));
+    });
+
+    it('matches valid username searches', () => {
+      assert.isTrue(isUsernameValid('username.01'));
+      assert.isTrue(isUsernameValid('username.12'));
+      assert.isTrue(isUsernameValid('xyz.568'));
+      assert.isTrue(isUsernameValid('numbered9.34'));
+      assert.isTrue(isUsernameValid('u12.34'));
+      assert.isTrue(isUsernameValid('with_underscore.56'));
+      assert.isTrue(isUsernameValid('username_with_32_characters_1234.45'));
+    });
+
+    it('does not match when then username starts with a number', () => {
+      assert.isFalse(isUsernameValid('1user.12'));
+      assert.isFalse(isUsernameValid('9user_name.12'));
+    });
+
+    it('does not match usernames shorter than 3 characters or longer than 32', () => {
+      assert.isFalse(isUsernameValid('us.12'));
+      assert.isFalse(isUsernameValid('username_with_33_characters_12345.67'));
+    });
+
+    it('does not match something that looks like a phone number', () => {
+      assert.isFalse(isUsernameValid('+'));
+      assert.isFalse(isUsernameValid('2223'));
+      assert.isFalse(isUsernameValid('+3'));
+      assert.isFalse(isUsernameValid('+234234234233'));
+    });
+
+    it('does not match invalid discriminators', () => {
+      assert.isFalse(isUsernameValid('username.0'));
+      assert.isFalse(isUsernameValid('username.00'));
+      assert.isFalse(isUsernameValid('username.000'));
+      assert.isFalse(isUsernameValid('username.001'));
+      assert.isFalse(isUsernameValid('username.012'));
+    });
+  });
+
   describe('getUsernameFromSearch', () => {
     const { getUsernameFromSearch } = Username;
 
     it('matches partial username searches without discriminator', () => {
-      assert.strictEqual(getUsernameFromSearch('use'), 'use.01');
-      assert.strictEqual(getUsernameFromSearch('user'), 'user.01');
-      assert.strictEqual(getUsernameFromSearch('usern'), 'usern.01');
-      assert.strictEqual(getUsernameFromSearch('usern.'), 'usern.01');
+      assert.strictEqual(getUsernameFromSearch('use'), 'use');
+      assert.strictEqual(getUsernameFromSearch('user'), 'user');
+      assert.strictEqual(getUsernameFromSearch('usern'), 'usern');
+      assert.strictEqual(getUsernameFromSearch('usern.'), 'usern.');
     });
 
     it('matches and strips leading @', () => {
-      assert.strictEqual(getUsernameFromSearch('@user'), 'user.01');
-      assert.strictEqual(getUsernameFromSearch('@user.'), 'user.01');
+      assert.strictEqual(getUsernameFromSearch('@user'), 'user');
+      assert.strictEqual(getUsernameFromSearch('@user.'), 'user.');
       assert.strictEqual(getUsernameFromSearch('@user.01'), 'user.01');
     });
 
-    it('adds a 1 if discriminator is one digit', () => {
-      assert.strictEqual(getUsernameFromSearch('@user.0'), 'user.01');
-      assert.strictEqual(getUsernameFromSearch('@user.2'), 'user.21');
-    });
-
     it('matches valid username searches', () => {
       assert.strictEqual(getUsernameFromSearch('username.12'), 'username.12');
       assert.strictEqual(getUsernameFromSearch('xyz.568'), 'xyz.568');

ts/util/Username.dom.ts

@@ -2,6 +2,7 @@
 // SPDX-License-Identifier: AGPL-3.0-only
 
 import * as RemoteConfig from '../RemoteConfig.dom.js';
+import { getDiscriminator, getNickname } from '../types/Username.std.js';
 import { parseIntWithFallback } from './parseIntWithFallback.std.js';
 
 export function getMaxNickname(): number {
@@ -15,9 +16,42 @@ export function getMinNickname(): number {
 }
 
 // Usernames have a minimum length of 3 and maximum of 32
-const USERNAME_CHARS = /^@?[a-zA-Z_][a-zA-Z0-9_]{2,31}(.\d+)?$/;
+const USERNAME_LIKE = /^@?[a-zA-Z_][a-zA-Z0-9_]{2,31}(.\d*?)?$/;
+const NICKNAME_CHARS = /^[a-zA-Z_][a-zA-Z0-9_]+$/;
 const ALL_DIGITS = /^\d+$/;
 
+export function isUsernameValid(username: string): boolean {
+  const nickname = getNickname(username);
+  const discriminator = getDiscriminator(username);
+
+  if (!nickname) {
+    return false;
+  }
+
+  if (
+    nickname.length < getMinNickname() ||
+    nickname.length > getMaxNickname()
+  ) {
+    return false;
+  }
+
+  if (!NICKNAME_CHARS.test(nickname)) {
+    return false;
+  }
+
+  if (!discriminator || discriminator.length === 0) {
+    return false;
+  }
+  if (discriminator[0] === '0' && discriminator[1] === '0') {
+    return false;
+  }
+  if (discriminator[0] === '0' && discriminator.length !== 2) {
+    return false;
+  }
+
+  return true;
+}
+
 export function getUsernameFromSearch(searchTerm: string): string | undefined {
   let modifiedTerm = searchTerm.trim();
 
@@ -28,26 +62,12 @@ export function getUsernameFromSearch(searchTerm: string): string | undefined {
   if (modifiedTerm.startsWith('@')) {
     modifiedTerm = modifiedTerm.slice(1);
   }
-  if (modifiedTerm.endsWith('.')) {
-    // Allow nicknames without full discriminator
-    modifiedTerm = `${modifiedTerm}01`;
-  } else if (/\.\d$/.test(modifiedTerm)) {
-    // Add one more digit if they only have one
-    modifiedTerm = `${modifiedTerm}1`;
-  } else if (!/\.\d*$/.test(modifiedTerm)) {
-    // Allow nicknames without discriminator
-    modifiedTerm = `${modifiedTerm}.01`;
-  }
 
-  if (!USERNAME_CHARS.test(modifiedTerm)) {
+  if (!USERNAME_LIKE.test(modifiedTerm)) {
     return undefined;
   }
 
-  try {
-    return modifiedTerm;
-  } catch {
-    return undefined;
-  }
+  return modifiedTerm;
 }
 
 export function isProbablyAUsername(text: string): boolean {
@@ -57,7 +77,7 @@ export function isProbablyAUsername(text: string): boolean {
     return true;
   }
 
-  if (!USERNAME_CHARS.test(searchTerm)) {
+  if (!USERNAME_LIKE.test(searchTerm)) {
     return false;
   }
   if (ALL_DIGITS.test(searchTerm)) {