TS extension: add related-files call to CopilotRelated

registerRelatedFilesProvider is a new method on the copilot extension.
CopilotRelated is a new tsserver command that provides information from
tsserver to copilot. (The information is not necessarily
copilot-specific, of course.)

extensions/typescript-language-features/src/typeScriptServiceClientHost.ts

@@ -9,6 +9,7 @@
  * ------------------------------------------------------------------------------------------ */
 
 import * as vscode from 'vscode';
+import { URI } from 'vscode-uri';
 import { CommandManager } from './commands/commandManager';
 import { ServiceConfigurationProvider } from './configuration/configuration';
 import { DiagnosticLanguage, LanguageDescription } from './configuration/languageDescription';
@@ -35,6 +36,7 @@ import TypingsStatus, { AtaProgressReporter } from './ui/typingsStatus';
 import { VersionStatus } from './ui/versionStatus';
 import { coalesce } from './utils/arrays';
 import { Disposable } from './utils/dispose';
+import { jsTsLanguageModes, isSupportedLanguageMode } from './configuration/languageIds';
 
 // Style check diagnostics that can be reported as warnings
 const styleCheckDiagnostics = new Set([
@@ -119,7 +121,7 @@ export default class TypeScriptServiceClientHost extends Disposable {
 			this._register(module.register(this.client, allModeIds)));
 
 		this.client.ensureServiceStarted();
-		this.client.onReady(() => {
+		this.client.onReady(async () => {
 			const languages = new Set<string>();
 			for (const plugin of services.pluginManager.plugins) {
 				if (plugin.configNamespace && plugin.languages.length) {
@@ -150,6 +152,60 @@ export default class TypeScriptServiceClientHost extends Disposable {
 					standardFileExtensions: [],
 				}, onCompletionAccepted);
 			}
+			// TODO: Still probably isn't the right place for this
+			const ext = vscode.extensions.getExtension('github.copilot');
+			if (!ext) {
+				vscode.window.showErrorMessage(vscode.l10n.t('Could not find related-files extension'));
+				return;
+			}
+			await ext.activate();
+			const relatedAPI = ext.exports as {
+				registerRelatedFilesProvider(
+					providerId: { extensionId: string; languageId: string },
+					callback: (uri: vscode.Uri) => Promise<{ entries: vscode.Uri[]; traits?: { name: string; value: string }[] }>
+				): void;
+			} | undefined;
+			if (relatedAPI) {
+				for (const languageId of jsTsLanguageModes) {
+					const id = {
+						extensionId: 'vscode.typescript-language-features',
+						languageId
+					};
+					relatedAPI.registerRelatedFilesProvider(id, async uri => {
+						let document;
+						try {
+							document = await vscode.workspace.openTextDocument(uri);
+						} catch {
+							if (!vscode.window.activeTextEditor) {
+								vscode.window.showErrorMessage(vscode.l10n.t("Go to Source Definition failed. No resource provided."));
+								return [];
+							}
+							// something is REALLY wrong if you can't open the active text editor's document, so don't catch that
+							document = await vscode.workspace.openTextDocument(vscode.window.activeTextEditor.document.uri);
+						}
+
+						if (!isSupportedLanguageMode(document)) {
+							vscode.window.showErrorMessage(vscode.l10n.t("Go to Source Definition failed. Unsupported file type."));
+							return [];
+						}
+
+						const file = this.client.toOpenTsFilePath(document);
+						if (!file) {
+							return [];
+						}
+						// TODO: This compiles but will never cancel; this needs a token that somebody might actually cancel.
+						const cancel = new vscode.CancellationTokenSource();
+						const response = await this.client.execute('getImports', { file, }, cancel.token);
+						if (response.type !== 'response' || !response.body) {
+							return [];
+						}
+						return response.body.map(URI.file);
+					});
+				}
+			}
+			else {
+				vscode.window.showErrorMessage(vscode.l10n.t('Could not find github.copilot extension'));
+			}
 		});
 
 		this.client.onTsServerStarted(() => {

extensions/typescript-language-features/src/typescriptService.ts

@@ -77,6 +77,7 @@ interface StandardTsServerRequests {
 	'getMoveToRefactoringFileSuggestions': [Proto.GetMoveToRefactoringFileSuggestionsRequestArgs, Proto.GetMoveToRefactoringFileSuggestions];
 	'linkedEditingRange': [Proto.FileLocationRequestArgs, Proto.LinkedEditingRangeResponse];
 	'mapCode': [Proto.MapCodeRequestArgs, Proto.MapCodeResponse];
+	'getImports': [Proto.GetImportRequestArgs, Proto.GetImportResponse];
 	'getPasteEdits': [Proto.GetPasteEditsRequestArgs, Proto.GetPasteEditsResponse];
 	'preparePasteEdits': [Proto.PreparePasteEditsRequestArgs, Proto.PreparePasteEditsResponse];
 }