Upgrade ESLint to v9 with flat config

eslint.config.mjs

@@ -0,0 +1,189 @@
+// @ts-check
+import eslint from "@eslint/js";
+import { defineConfig } from "eslint/config";
+import markdown from "@eslint/markdown";
+import tseslint from "typescript-eslint";
+import prettierConfig from "eslint-config-prettier";
+import prettierPlugin from "eslint-plugin-prettier";
+import { createTypeScriptImportResolver } from "eslint-import-resolver-typescript";
+import { flatConfigs as importXFlatConfigs } from "eslint-plugin-import-x";
+import packageJson from "eslint-plugin-package-json";
+import globals from "globals";
+
+export default defineConfig(
+	// Global ignores
+	{
+		ignores: [
+			"out/**",
+			"dist/**",
+			"**/*.d.ts",
+			"vitest.config.ts",
+			".vscode-test/**",
+		],
+	},
+
+	// Base ESLint recommended rules (for JS/TS files only)
+	{
+		files: ["**/*.ts", "**/*.js", "**/*.mjs"],
+		...eslint.configs.recommended,
+	},
+
+	// TypeScript configuration with type-checked rules
+	{
+		files: ["**/*.ts"],
+		extends: [
+			...tseslint.configs.recommendedTypeChecked,
+			...tseslint.configs.stylisticTypeChecked,
+			importXFlatConfigs.typescript,
+		],
+		languageOptions: {
+			parserOptions: {
+				projectService: true,
+				tsconfigRootDir: import.meta.dirname,
+			},
+		},
+		plugins: {
+			prettier: prettierPlugin,
+		},
+		settings: {
+			"import-x/resolver-next": [
+				createTypeScriptImportResolver({ project: "./tsconfig.json" }),
+			],
+			"import-x/internal-regex": "^@/",
+		},
+		rules: {
+			// Prettier integration
+			"prettier/prettier": "error",
+
+			// Core ESLint rules
+			curly: "error",
+			eqeqeq: "error",
+			"no-throw-literal": "error",
+			"no-console": "error",
+
+			// TypeScript rules (extending/overriding presets)
+			"require-await": "off",
+			"@typescript-eslint/require-await": "error",
+			"@typescript-eslint/consistent-type-imports": "error",
+			"@typescript-eslint/switch-exhaustiveness-check": [
+				"error",
+				{ considerDefaultExhaustiveForUnions: true },
+			],
+			"@typescript-eslint/no-unused-vars": [
+				"error",
+				{ varsIgnorePattern: "^_" },
+			],
+			"@typescript-eslint/array-type": ["error", { default: "array-simple" }],
+			"@typescript-eslint/prefer-nullish-coalescing": [
+				"error",
+				// Allow || for strings where empty string should be treated as falsy
+				{ ignorePrimitives: { string: true } },
+			],
+			"@typescript-eslint/dot-notation": [
+				"error",
+				// Allow bracket notation for index signatures (e.g., Record<string, T>)
+				{ allowIndexSignaturePropertyAccess: true },
+			],
+
+			// Import rules
+			"import-x/order": [
+				"error",
+				{
+					groups: [
+						["builtin", "external"],
+						"internal",
+						"parent",
+						["sibling", "index"],
+						"type",
+					],
+					pathGroups: [
+						{ pattern: "@/**", group: "internal", position: "before" },
+					],
+					pathGroupsExcludedImportTypes: ["builtin", "external"],
+					"newlines-between": "always",
+					alphabetize: { order: "asc", caseInsensitive: true },
+					sortTypesGroup: true,
+				},
+			],
+			"no-duplicate-imports": "off",
+			"import-x/no-duplicates": ["error", { "prefer-inline": true }],
+			"import-x/no-unresolved": ["error", { ignore: ["vscode"] }],
+
+			// Custom AST selector rule
+			"no-restricted-syntax": [
+				"error",
+				{
+					selector:
+						"CallExpression[callee.property.name='executeCommand'][arguments.0.value='setContext'][arguments.length>=3]",
+					message:
+						"Do not use executeCommand('setContext', ...) directly. Use the ContextManager class instead.",
+				},
+			],
+		},
+	},
+
+	// Test files - use test tsconfig and relax some rules
+	{
+		files: ["test/**/*.ts", "**/*.test.ts", "**/*.spec.ts"],
+		settings: {
+			"import-x/resolver-next": [
+				createTypeScriptImportResolver({ project: "test/tsconfig.json" }),
+			],
+		},
+		rules: {
+			// Allow type annotations in tests (e.g., for vi.fn<SomeType>())
+			"@typescript-eslint/consistent-type-imports": [
+				"error",
+				{
+					disallowTypeAnnotations: false,
+				},
+			],
+			// vitest mocks trigger false positives for unbound-method
+			"@typescript-eslint/unbound-method": "off",
+			// Empty callbacks are common in test stubs
+			"@typescript-eslint/no-empty-function": "off",
+			// Test mocks often have loose typing - relax unsafe rules
+			"@typescript-eslint/no-unsafe-assignment": "off",
+			"@typescript-eslint/no-unsafe-call": "off",
+			"@typescript-eslint/no-unsafe-return": "off",
+		},
+	},
+
+	// Disable no-restricted-syntax for contextManager
+	{
+		files: ["src/core/contextManager.ts"],
+		rules: {
+			"no-restricted-syntax": "off",
+		},
+	},
+
+	// Webpack config - CommonJS with Node globals
+	{
+		files: ["webpack.config.js"],
+		languageOptions: {
+			globals: {
+				...globals.node,
+			},
+		},
+	},
+
+	// Package.json linting
+	packageJson.configs.recommended,
+
+	// Markdown linting with GitHub-flavored admonitions allowed
+	...markdown.configs.recommended,
+	{
+		files: ["**/*.md"],
+		rules: {
+			"markdown/no-missing-label-refs": [
+				"error",
+				{
+					allowLabels: ["!NOTE", "!TIP", "!IMPORTANT", "!WARNING", "!CAUTION"],
+				},
+			],
+		},
+	},
+
+	// Prettier must be last to override other formatting rules
+	prettierConfig,
+);

package.json

@@ -20,7 +20,7 @@
 	"scripts": {
 		"build": "webpack",
 		"fmt": "prettier --write .",
-		"lint": "eslint . --ext ts,md,json",
+		"lint": "eslint .",
 		"lint:fix": "yarn lint --fix",
 		"package": "webpack --mode production --devtool hidden-source-map",
 		"package:prerelease": "npx vsce package --pre-release",
@@ -418,35 +418,37 @@
 		"zod": "^4.3.2"
 	},
 	"devDependencies": {
-		"@types/eventsource": "^3.0.0",
-		"@types/node": "^22.14.1",
+		"@eslint/js": "^9.39.2",
+		"@eslint/markdown": "^7.5.1",
+		"@types/node": "^18",
 		"@types/proper-lockfile": "^4.1.4",
 		"@types/semver": "^7.7.1",
 		"@types/ua-parser-js": "0.7.39",
 		"@types/vscode": "^1.73.0",
 		"@types/ws": "^8.18.1",
-		"@typescript-eslint/eslint-plugin": "^8.49.0",
-		"@typescript-eslint/parser": "^8.50.1",
+		"@typescript-eslint/eslint-plugin": "^8.52.0",
+		"@typescript-eslint/parser": "^8.52.0",
 		"@vitest/coverage-v8": "^4.0.16",
 		"@vscode/test-cli": "^0.0.12",
+		"@vscode/test-electron": "^2.5.2",
 		"@vscode/vsce": "^3.7.1",
-		"bufferutil": "^4.0.9",
+		"bufferutil": "^4.1.0",
 		"coder": "https://github.com/coder/coder#main",
 		"dayjs": "^1.11.19",
-		"electron": "^39.2.6",
-		"eslint": "^8.57.1",
+		"electron": "^39.2.7",
+		"eslint": "^9.39.2",
 		"eslint-config-prettier": "^10.1.8",
 		"eslint-import-resolver-typescript": "^4.4.4",
-		"eslint-plugin-import": "^2.32.0",
-		"eslint-plugin-md": "^1.0.19",
-		"eslint-plugin-package-json": "^0.85.0",
+		"eslint-plugin-import-x": "^4.16.1",
+		"eslint-plugin-package-json": "^0.88.1",
 		"eslint-plugin-prettier": "^5.5.4",
+		"globals": "^16.5.0",
 		"jsonc-eslint-parser": "^2.4.2",
-		"markdown-eslint-parser": "^1.2.1",
 		"memfs": "^4.51.1",
 		"prettier": "^3.7.4",
 		"ts-loader": "^9.5.4",
 		"typescript": "^5.9.3",
+		"typescript-eslint": "^8.52.0",
 		"utf-8-validate": "^6.0.6",
 		"vitest": "^4.0.16",
 		"webpack": "^5.104.1",

src/api/agentMetadataHelper.ts

@@ -8,12 +8,12 @@ import {
 } from "./api-helper";
 import { type CoderApi } from "./coderApi";
 
-export type AgentMetadataWatcher = {
+export interface AgentMetadataWatcher {
 	onChange: vscode.EventEmitter<null>["event"];
 	dispose: () => void;
 	metadata?: AgentMetadataEvent[];
 	error?: unknown;
-};
+}
 
 /**
  * Opens a websocket connection to watch metadata for a given workspace agent.