fix: resolve extension install 404 and language pack detection

src/vs/platform/languagePacks/browser/languagePacks.ts

@@ -7,11 +7,15 @@ import { URI } from '../../../base/common/uri.js';
 import { ILanguagePackItem, ILanguagePackService } from '../common/languagePacks.js';
 import { IExtensionGalleryService } from '../../extensionManagement/common/extensionManagement.js';
 import { CancellationToken } from '../../../base/common/cancellation.js';
+import { IExtensionService } from '../../../workbench/services/extensions/common/extensions.js';
 
 export class WebLanguagePacksService implements ILanguagePackService {
 	declare readonly _serviceBrand: undefined;
 
-	constructor(@IExtensionGalleryService private readonly galleryService: IExtensionGalleryService) {}
+	constructor(
+		@IExtensionGalleryService private readonly galleryService: IExtensionGalleryService,
+		@IExtensionService private readonly extensionService: IExtensionService
+	) {}
 
 	async getBuiltInExtensionTranslationsUri(_id: string, _language: string): Promise<URI | undefined> {
 		return undefined;
@@ -45,20 +49,43 @@ export class WebLanguagePacksService implements ILanguagePackService {
 	}
 
 	async getInstalledLanguages(): Promise<ILanguagePackItem[]> {
+		const items: ILanguagePackItem[] = [];
+		const seen = new Set<string>();
+
+		// Check localStorage for explicitly set locale
 		const extensionId = localStorage.getItem('vscode.nls.languagePackExtensionId');
 		const locale = localStorage.getItem('vscode.nls.locale');
 
-		if (!extensionId || !locale) {
-			return [];
-		}
-
-		return [
-			{
+		if (extensionId && locale) {
+			items.push({
 				id: locale,
 				label: this.getLanguageLabel(locale),
 				extensionId
+			});
+			seen.add(locale.toLowerCase());
+		}
+
+		// Also scan installed extensions for language packs
+		try {
+			const extensions = this.extensionService.extensions;
+			for (const ext of extensions) {
+				if (ext.identifier && ext.name.startsWith('vscode-language-pack-')) {
+					const extLocale = this.getLocaleFromExtensionName(ext.name);
+					if (extLocale && !seen.has(extLocale.toLowerCase())) {
+						items.push({
+							id: extLocale,
+							label: this.getLanguageLabel(extLocale),
+							extensionId: ext.identifier.value
+						});
+						seen.add(extLocale.toLowerCase());
+					}
+				}
 			}
-		];
+		} catch {
+			// ignore errors scanning extensions
+		}
+
+		return items;
 	}
 
 	private getLanguageLabel(locale: string): string {
@@ -80,4 +107,16 @@ export class WebLanguagePacksService implements ILanguagePackService {
 		};
 		return labels[locale.toLowerCase()] ?? locale;
 	}
+
+	// Map extension name suffixes to locale codes
+	// e.g. vscode-language-pack-zh-hans -> zh-cn
+	private getLocaleFromExtensionName(name: string): string | undefined {
+		const nameToLocale: Record<string, string> = {
+			'zh-hans': 'zh-cn',
+			'zh-hant': 'zh-tw',
+			'pt-br': 'pt-br'
+		};
+		const suffix = name.replace('vscode-language-pack-', '');
+		return nameToLocale[suffix] ?? suffix;
+	}
 }

src/vs/workbench/services/extensionManagement/browser/webExtensionsScannerService.ts

@@ -877,16 +877,37 @@ export class WebExtensionsScannerService extends Disposable implements IWebExten
 		galleryExtension: IGalleryExtension,
 		metadata?: Metadata
 	): Promise<IWebExtension> {
-		const extensionLocation = await this.extensionResourceLoaderService.getExtensionGalleryResourceURL(
-			{
-				publisher: galleryExtension.publisher,
-				name: galleryExtension.name,
-				version: galleryExtension.version,
-				targetPlatform:
-					galleryExtension.properties.targetPlatform === TargetPlatform.WEB ? TargetPlatform.WEB : undefined
-			},
-			'extension'
-		);
+		// Use the gallery extension's manifest asset URL directly (already proxied
+		// correctly by the marketplace proxy for both Microsoft and Open VSX sources)
+		// instead of constructing a URL from resourceUrlTemplate which may point to
+		// a version that doesn't exist on Open VSX.
+		let manifest: IExtensionManifest | undefined;
+		let extensionLocation: URI | undefined;
+
+		if (galleryExtension.assets.manifest) {
+			try {
+				const manifestUri = URI.parse(galleryExtension.assets.manifest.uri);
+				const content = await this.extensionResourceLoaderService.readExtensionResource(manifestUri);
+				manifest = JSON.parse(content);
+				// Use the manifest URI's directory as the extension location
+				extensionLocation = joinPath(manifestUri, '..');
+			} catch (error) {
+				this.logService.warn(`Failed to fetch manifest from gallery asset, falling back to resourceUrlTemplate`, getErrorMessage(error));
+			}
+		}
+
+		if (!extensionLocation) {
+			extensionLocation = await this.extensionResourceLoaderService.getExtensionGalleryResourceURL(
+				{
+					publisher: galleryExtension.publisher,
+					name: galleryExtension.name,
+					version: galleryExtension.version,
+					targetPlatform:
+						galleryExtension.properties.targetPlatform === TargetPlatform.WEB ? TargetPlatform.WEB : undefined
+				},
+				'extension'
+			);
+		}
 
 		if (!extensionLocation) {
 			throw new Error('No extension gallery service configured.');
@@ -897,7 +918,8 @@ export class WebExtensionsScannerService extends Disposable implements IWebExten
 			galleryExtension.identifier,
 			galleryExtension.assets.readme ? URI.parse(galleryExtension.assets.readme.uri) : undefined,
 			galleryExtension.assets.changelog ? URI.parse(galleryExtension.assets.changelog.uri) : undefined,
-			metadata
+			metadata,
+			manifest
 		);
 	}
 
@@ -906,7 +928,8 @@ export class WebExtensionsScannerService extends Disposable implements IWebExten
 		identifier?: IExtensionIdentifier,
 		readmeUri?: URI,
 		changelogUri?: URI,
-		metadata?: Metadata
+		metadata?: Metadata,
+		manifest?: IExtensionManifest
 	): Promise<IWebExtension> {
 		const extensionResources = await this.listExtensionResources(extensionLocation);
 		const packageNLSResources = this.getPackageNLSResourceMapFromResources(extensionResources);
@@ -916,7 +939,7 @@ export class WebExtensionsScannerService extends Disposable implements IWebExten
 		return this.toWebExtension(
 			extensionLocation,
 			identifier,
-			undefined,
+			manifest,
 			packageNLSResources,
 			fallbackPackageNLSResource ? URI.parse(fallbackPackageNLSResource) : null,
 			readmeUri,