Migrate to eslint flat config (microsoft#3123)

resolve microsoft#3121
same change in typespec-azure
Azure/typespec-azure#620

## Single top level config
This makes it a little nicer to run as you know get the absolute path
for errors
No need to have the hacky rushstack dependency to allow using the same
shared config.

## Able to lint the projects that are outside of the pnpm workspace
<img width="1054" alt="image"
src="https://github.com/microsoft/typespec/assets/1031227/f88691d9-1bf2-4140-ba2b-533207b15f9d">


## Eslint 9 -no yet

eslint 9 was just released firday which makes this config the new
default however it does include breaking changes and not all our plugins
have updated

Author: timotheeguerin

.chronus/changes/eslint-flat-config-2024-3-5-19-46-26.md

@@ -0,0 +1,25 @@
+---
+# Change versionKind to one of: internal, fix, dependencies, feature, deprecation, breaking
+changeKind: internal
+packages:
+  - "@typespec/bundler"
+  - "@typespec/compiler"
+  - "@typespec/eslint-plugin"
+  - "@typespec/html-program-viewer"
+  - "@typespec/http"
+  - "@typespec/internal-build-utils"
+  - "@typespec/json-schema"
+  - "@typespec/library-linter"
+  - "@typespec/openapi"
+  - "@typespec/openapi3"
+  - "@typespec/playground"
+  - "@typespec/prettier-plugin-typespec"
+  - "@typespec/protobuf"
+  - "@typespec/rest"
+  - tmlanguage-generator
+  - typespec-vscode
+  - "@typespec/versioning"
+  - "typespec-vs"
+---
+
+Migrate to eslint flat config

.vscode/settings.json

@@ -59,5 +59,6 @@
   "prettier.prettierPath": "./node_modules/prettier/index.cjs",
   "prettier.documentSelectors": ["**/*.tsp"],
   "testExplorer.errorDecoration": false,
-  "typespec.tsp-server.path": "${workspaceFolder}/packages/compiler"
+  "typespec.tsp-server.path": "${workspaceFolder}/packages/compiler",
+  "eslint.experimental.useFlatConfig": true // Still needed new version coming soon should work without https://github.com/microsoft/vscode-eslint/issues/1644
 }

e2e/e2e-tests.js

@@ -1,3 +1,4 @@
+/* eslint-disable no-console */
 // @ts-check
 import { existsSync, readdirSync, rmSync, writeFileSync } from "fs";
 import { join } from "path";

eslint.config.js

@@ -0,0 +1,128 @@
+// @ts-check
+import eslint from "@eslint/js";
+import deprecation from "eslint-plugin-deprecation";
+import unicorn from "eslint-plugin-unicorn";
+import vitest from "eslint-plugin-vitest";
+import { dirname } from "path";
+import tsEslint from "typescript-eslint";
+import { fileURLToPath } from "url";
+
+/** Config that will apply to all files */
+const allFilesConfig = tsEslint.config({
+  plugins: {
+    unicorn,
+  },
+  rules: {
+    /**
+     * Typescript plugin overrides
+     */
+    "@typescript-eslint/no-non-null-assertion": "off",
+    "@typescript-eslint/no-explicit-any": "off",
+    "@typescript-eslint/no-inferrable-types": "off",
+    "@typescript-eslint/no-empty-function": "off",
+    "@typescript-eslint/no-empty-interface": "off",
+    "@typescript-eslint/no-unused-vars": [
+      "warn",
+      { varsIgnorePattern: "^_", argsIgnorePattern: ".*", ignoreRestSiblings: true },
+    ],
+
+    // This rule is bugged https://github.com/typescript-eslint/typescript-eslint/issues/6538
+    "@typescript-eslint/no-misused-promises": "off",
+
+    /**
+     * Unicorn
+     */
+    "unicorn/filename-case": ["error", { case: "kebabCase" }],
+
+    /**
+     * Core
+     */
+    "no-inner-declarations": "off",
+    "no-empty": "off",
+    "no-constant-condition": "off",
+    "no-case-declarations": "off",
+    "no-ex-assign": "off",
+    "no-undef": "off",
+    "prefer-const": [
+      "warn",
+      {
+        destructuring: "all",
+      },
+    ],
+    eqeqeq: ["warn", "always", { null: "ignore" }],
+
+    // Do not want console.log left from debugging or using console.log for logging. Use the program logger.
+    "no-console": "warn",
+
+    // Symbols should have a description so it can be serialized.
+    "symbol-description": "warn",
+  },
+});
+
+/** Config that will apply to all typescript files only
+ * @param {string} root
+ */
+export function getTypeScriptProjectRules(root) {
+  return tsEslint.config({
+    files: ["**/*.ts", "**/*.tsx"],
+    plugins: {
+      deprecation,
+    },
+    languageOptions: {
+      parserOptions: {
+        project: "./tsconfig.json",
+        tsconfigRootDir: root,
+      },
+    },
+    rules: {
+      // Only put rules here that need typescript project information
+      "@typescript-eslint/no-floating-promises": "error",
+      "deprecation/deprecation": ["warn"],
+    },
+  });
+}
+
+/** Config that will apply to all test files only */
+const testFilesConfig = tsEslint.config({
+  /**
+   * Test files specific rules
+   */
+  files: ["**/*.test.ts"],
+  plugins: { vitest },
+  rules: {
+    "vitest/no-focused-tests": "warn",
+    "vitest/no-identical-title": "error",
+    "vitest/no-commented-out-tests": "warn",
+    "vitest/no-import-node-test": "warn",
+    "vitest/require-local-test-context-for-concurrent-snapshots": "warn",
+    "vitest/valid-describe-callback": "warn",
+    "vitest/valid-expect": "warn",
+    "@typescript-eslint/no-non-null-asserted-optional-chain": "off",
+  },
+});
+
+export const TypeSpecCommonEslintConfigs = [
+  eslint.configs.recommended,
+  ...tsEslint.configs.recommended,
+  ...allFilesConfig,
+  ...testFilesConfig,
+];
+
+export default tsEslint.config(
+  {
+    ignores: [
+      "**/dist/**/*",
+      "**/.temp/**/*",
+      "**/generated-defs/*",
+      "**/website/build/**/*",
+      "**/.docusaurus/**/*",
+      "packages/compiler/templates/**/*", // Ignore the templates which might have invalid code and not follow exactly our rules.
+      // TODO: enable
+      "**/.scripts/**/*",
+      "eng/scripts/**/*",
+      "packages/*/scripts/**/*",
+    ],
+  },
+  ...TypeSpecCommonEslintConfigs,
+  ...getTypeScriptProjectRules(dirname(fileURLToPath(import.meta.url)))
+);

package.json

@@ -3,6 +3,7 @@
   "version": "0.0.1",
   "private": true,
   "packageManager": "pnpm@8.13.1",
+  "type": "module",
   "scripts": {
     "build": "pnpm build:all && pnpm gen-compiler-extern-signature",
     "build:all": "pnpm -r --workspace-concurrency=Infinity --aggregate-output --reporter=append-only build  && pnpm gen-compiler-extern-signature",
@@ -17,7 +18,8 @@
     "format:check": "prettier . --check",
     "format:dir": "prettier --write",
     "gen-compiler-extern-signature": "pnpm run -r --filter \"@typespec/compiler\"  gen-extern-signature",
-    "lint": "pnpm -r --parallel --aggregate-output --reporter=append-only run lint",
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix",
     "merge-coverage": "c8 -- report --reporter=cobertura --reporter=text",
     "pack:all": "chronus pack --pack-destination ./temp/artifacts",
     "preinstall": "npx only-allow pnpm",
@@ -34,14 +36,24 @@
   "devDependencies": {
     "@chronus/chronus": "^0.8.3",
     "@chronus/github": "^0.2.2",
+    "@eslint/js": "^8.57.0",
     "@pnpm/find-workspace-packages": "^6.0.9",
+    "@types/node": "~18.11.19",
+    "@typescript-eslint/parser": "^7.5.0",
+    "@typescript-eslint/utils": "^7.5.0",
     "c8": "^9.1.0",
     "cspell": "^8.6.1",
+    "eslint": "^8.57.0",
+    "eslint-plugin-deprecation": "^2.0.0",
+    "eslint-plugin-import": "^2.29.1",
+    "eslint-plugin-unicorn": "^51.0.1",
+    "eslint-plugin-vitest": "^0.4.1",
     "prettier": "~3.2.5",
     "prettier-plugin-organize-imports": "~3.2.4",
     "rimraf": "~5.0.5",
     "syncpack": "^12.3.0",
     "typescript": "~5.4.3",
+    "typescript-eslint": "^7.5.0",
     "vitest": "^1.4.0"
   },
   "syncpack": {

packages/best-practices/.eslintrc.cjs

@@ -32,8 +32,8 @@
     "test": "vitest run",
     "test:ui": "vitest --ui",
     "test:ci": "vitest run --coverage --reporter=junit --reporter=default",
-    "lint": "eslint . --ext .ts --max-warnings=0",
-    "lint:fix": "eslint . --fix --ext .ts"
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix"
   },
   "files": [
     "lib/*.tsp",
@@ -46,12 +46,9 @@
   "devDependencies": {
     "@types/node": "~18.11.19",
     "@typespec/compiler": "workspace:~",
-    "@typespec/eslint-config-typespec": "workspace:~",
-    "@typespec/eslint-plugin": "workspace:~",
     "@vitest/coverage-v8": "^1.4.0",
     "@vitest/ui": "^1.4.0",
     "c8": "^9.1.0",
-    "eslint": "^8.57.0",
     "rimraf": "~5.0.5",
     "typescript": "~5.4.3",
     "vitest": "^1.4.0"

packages/best-practices/package.json

@@ -28,8 +28,8 @@
     "watch": "tsc -p . --watch",
     "test": "echo 'no test'",
     "test:ci": "echo 'no test'",
-    "lint": "eslint . --ext .ts --max-warnings=0",
-    "lint:fix": "eslint . --fix --ext .ts"
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix"
   },
   "files": [
     "lib/*.tsp",
@@ -48,11 +48,9 @@
   "devDependencies": {
     "@types/node": "~18.11.19",
     "@types/semver": "^7.5.8",
-    "@typespec/eslint-config-typespec": "workspace:~",
     "@vitest/coverage-v8": "^1.4.0",
     "@vitest/ui": "^1.4.0",
     "c8": "^9.1.0",
-    "eslint": "^8.57.0",
     "rimraf": "~5.0.5",
     "typescript": "~5.4.3",
     "vitest": "^1.4.0"

packages/bundle-uploader/.eslintrc.cjs

@@ -33,8 +33,8 @@
     "test": "vitest run",
     "test:ui": "vitest --ui",
     "test:ci": "vitest run --coverage --reporter=junit --reporter=default",
-    "lint": "eslint . --ext .ts --max-warnings=0",
-    "lint:fix": "eslint . --fix --ext .ts"
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix"
   },
   "files": [
     "lib/*.tsp",
@@ -56,11 +56,9 @@
   "devDependencies": {
     "@types/node": "~18.11.19",
     "@types/yargs": "~17.0.32",
-    "@typespec/eslint-config-typespec": "workspace:~",
     "@vitest/coverage-v8": "^1.4.0",
     "@vitest/ui": "^1.4.0",
     "c8": "^9.1.0",
-    "eslint": "^8.57.0",
     "rimraf": "~5.0.5",
     "typescript": "~5.4.3",
     "vite": "^5.2.7",

packages/bundle-uploader/package.json

@@ -78,8 +78,8 @@
     "gen-manifest": "node scripts/generate-manifest.js",
     "regen-nonascii": "node scripts/regen-nonascii.js",
     "fuzz": "node dist/test/manual/fuzz.js run",
-    "lint": "eslint . --ext .ts --max-warnings=0",
-    "lint:fix": "eslint . --fix --ext .ts"
+    "lint": "eslint . --max-warnings=0",
+    "lint:fix": "eslint . --fix"
   },
   "dependencies": {
     "@babel/code-frame": "~7.24.2",
@@ -104,12 +104,10 @@
     "@types/semver": "^7.5.8",
     "@types/sinon": "~17.0.3",
     "@types/yargs": "~17.0.32",
-    "@typespec/eslint-config-typespec": "workspace:~",
     "@typespec/internal-build-utils": "workspace:~",
     "@vitest/coverage-v8": "^1.4.0",
     "@vitest/ui": "^1.4.0",
     "c8": "^9.1.0",
-    "eslint": "^8.57.0",
     "grammarkdown": "~3.3.2",
     "rimraf": "~5.0.5",
     "sinon": "~17.0.1",

packages/bundler/.eslintrc.cjs

@@ -0,0 +1,11 @@
+// @ts-check
+import eslint from "@eslint/js";
+import tsEslint from "typescript-eslint";
+
+export default tsEslint.config(
+  {
+    ignores: ["**/dist/**/*", "**/.temp/**/*"],
+  },
+  eslint.configs.recommended,
+  ...tsEslint.configs.recommended
+);

packages/bundler/package.json

@@ -0,0 +1,11 @@
+// @ts-check
+import eslint from "@eslint/js";
+import tsEslint from "typescript-eslint";
+
+export default tsEslint.config(
+  {
+    ignores: ["**/dist/**/*", "**/.temp/**/*"],
+  },
+  eslint.configs.recommended,
+  ...tsEslint.configs.recommended
+);