Fix offending l10n.t call and add an eslint rule to prevent it from happening

.eslint-plugin-local/code-no-localization-template-literals.ts

@@ -0,0 +1,90 @@
+/*---------------------------------------------------------------------------------------------
+ *  Copyright (c) Microsoft Corporation. All rights reserved.
+ *  Licensed under the MIT License. See License.txt in the project root for license information.
+ *--------------------------------------------------------------------------------------------*/
+
+import * as eslint from 'eslint';
+import { TSESTree } from '@typescript-eslint/utils';
+
+/**
+ * Prevents the use of template literals in localization function calls.
+ *
+ * vscode.l10n.t() and nls.localize() cannot handle string templating.
+ * Use placeholders instead: vscode.l10n.t('Message {0}', value)
+ *
+ * Examples:
+ * ❌ vscode.l10n.t(`Message ${value}`)
+ * ✅ vscode.l10n.t('Message {0}', value)
+ *
+ * ❌ nls.localize('key', `Message ${value}`)
+ * ✅ nls.localize('key', 'Message {0}', value)
+ */
+export default new class NoLocalizationTemplateLiterals implements eslint.Rule.RuleModule {
+
+	readonly meta: eslint.Rule.RuleMetaData = {
+		messages: {
+			noTemplateLiteral: 'Template literals cannot be used in localization calls. Use placeholders like {0}, {1} instead.'
+		},
+		docs: {
+			description: 'Prevents template literals in vscode.l10n.t() and nls.localize() calls',
+		},
+		schema: false,
+	};
+
+	create(context: eslint.Rule.RuleContext): eslint.Rule.RuleListener {
+
+		function checkCallExpression(node: TSESTree.CallExpression) {
+			const callee = node.callee;
+			let isLocalizationCall = false;
+			let isNlsLocalize = false;
+
+			// Check for vscode.l10n.t()
+			if (callee.type === 'MemberExpression') {
+				const object = callee.object;
+				const property = callee.property;
+
+				// vscode.l10n.t
+				if (object.type === 'MemberExpression') {
+					const outerObject = object.object;
+					const outerProperty = object.property;
+					if (outerObject.type === 'Identifier' && outerObject.name === 'vscode' &&
+						outerProperty.type === 'Identifier' && outerProperty.name === 'l10n' &&
+						property.type === 'Identifier' && property.name === 't') {
+						isLocalizationCall = true;
+					}
+				}
+
+				// l10n.t or nls.localize or any *.localize
+				if (object.type === 'Identifier' && property.type === 'Identifier') {
+					if (object.name === 'l10n' && property.name === 't') {
+						isLocalizationCall = true;
+					} else if (property.name === 'localize') {
+						isLocalizationCall = true;
+						isNlsLocalize = true;
+					}
+				}
+			}
+
+			if (!isLocalizationCall) {
+				return;
+			}
+
+			// For vscode.l10n.t(message, ...args) - check the first argument (message)
+			// For nls.localize(key, message, ...args) - check first two arguments (key and message)
+			const argsToCheck = isNlsLocalize ? 2 : 1;
+			for (let i = 0; i < argsToCheck && i < node.arguments.length; i++) {
+				const arg = node.arguments[i];
+				if (arg && arg.type === 'TemplateLiteral' && arg.expressions.length > 0) {
+					context.report({
+						node: arg,
+						messageId: 'noTemplateLiteral'
+					});
+				}
+			}
+		}
+
+		return {
+			CallExpression: (node: any) => checkCallExpression(node as TSESTree.CallExpression)
+		};
+	}
+};

eslint.config.js

@@ -90,6 +90,7 @@ export default tseslint.config(
 			'local/code-no-reader-after-await': 'warn',
 			'local/code-no-observable-get-in-reactive-context': 'warn',
 			'local/code-policy-localization-key-match': 'warn',
+			'local/code-no-localization-template-literals': 'error',
 			'local/code-no-deep-import-of-internal': ['error', { '.*Internal': true, 'searchExtTypesInternal': false }],
 			'local/code-layering': [
 				'warn',

extensions/typescript-language-features/src/languageFeatures/quickFix.ts

@@ -367,7 +367,7 @@ class TypeScriptQuickFixProvider implements vscode.CodeActionProvider<VsCodeCode
 			let title = action.description;
 			if (action.fixName === fixNames.classIncorrectlyImplementsInterface) {
 				title = vscode.l10n.t('{0} with AI', action.description);
-				message = vscode.l10n.t(`Implement the stubbed-out class members for ${document.getText(diagnostic.range)} with a useful implementation.`);
+				message = vscode.l10n.t('Implement the stubbed-out class members for {0} with a useful implementation.', document.getText(diagnostic.range));
 				expand = { kind: 'code-action', action };
 			} else if (action.fixName === fixNames.fixClassDoesntImplementInheritedAbstractMember) {
 				title = vscode.l10n.t('{0} with AI', action.description);