Support ESLint v9 (Excluding flat config support)

.github/workflows/ci-node.yml

@@ -27,7 +27,7 @@ jobs:
       fail-fast: false
       matrix:
         node: [18, 20]
-        eslint: ['^8.0.0']
+        eslint: ['8', '9.0.0-alpha.0']
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
@@ -41,15 +41,15 @@ jobs:
           node-version: ${{ matrix.node }}
           cache: 'pnpm'
       - name: Change ESLint version
-        run: pnpm add -w -D eslint@${{ matrix.eslint }}
+        run: pnpm add -w -D "eslint@${{ matrix.eslint }}"
       - run: pnpm run test
 
   e2e:
     strategy:
       fail-fast: false
       matrix:
         node: [18, 20]
-        eslint: ['^8.0.0']
+        eslint: ['8', '9.0.0-alpha.0']
         os: [ubuntu-latest, macos-latest, windows-latest]
     runs-on: ${{ matrix.os }}
     steps:
@@ -60,5 +60,5 @@ jobs:
           node-version: ${{ matrix.node }}
           cache: 'pnpm'
       - name: Change ESLint version
-        run: pnpm add -w -D eslint@${{ matrix.eslint }}
+        run: pnpm add -w -D "eslint@${{ matrix.eslint }}"
       - run: pnpm run e2e

e2e-test/global-installation/index.test.ts

@@ -34,7 +34,7 @@ test('can print error with eslint-formatter-codeframe', async () => {
       // merge stderr to stdout
       '2>&1',
     ],
-    { shell: true, stdio: 'pipe', cwd: __dirname },
+    { shell: true, stdio: 'pipe', cwd: __dirname, env: { ...process.env, ESLINT_USE_FLAT_CONFIG: 'false' } },
   );
   const streamWatcher = createStreamWatcher(child.stdout, { debug: true });
 

package.json

@@ -70,7 +70,7 @@
     "yargs": "^17.7.2"
   },
   "peerDependencies": {
-    "eslint": ">=8.45.0"
+    "eslint": ">=8.45.0, 9.0.0-alpha.0"
   },
   "engines": {
     "node": ">=18.0.0"
@@ -93,5 +93,10 @@
     "!src/**/__snapshots__",
     "dist",
     "static"
-  ]
+  ],
+  "pnpm": {
+    "patchedDependencies": {
+      "@types/eslint@8.44.6": "patches/@types__eslint@8.44.6.patch"
+    }
+  }
 }

patches/@types__eslint@8.44.6.patch

@@ -0,0 +1,89 @@
+diff --git a/index.d.ts b/index.d.ts
+index 538c0dc1851122fbba808968e02100c9ca5728c4..d16f8776837a844f5e8be9b4053386e53d495ef5 100644
+--- a/index.d.ts
++++ b/index.d.ts
+@@ -842,7 +842,7 @@ export class Linter {
+
+     version: string;
+
+-    constructor(options?: { cwd?: string | undefined; configType?: "flat" });
++    constructor(options?: { cwd?: string | undefined; configType?: "flat" | "eslintrc" });
+
+     verify(
+         code: SourceCode | string,
+diff --git a/use-at-your-own-risk.d.ts b/use-at-your-own-risk.d.ts
+index 089a657babec22d7bfa526d10d2950c77af041f3..31c56d1ed865fb11ba484efba01edc6ba7c57da9 100644
+--- a/use-at-your-own-risk.d.ts
++++ b/use-at-your-own-risk.d.ts
+@@ -1,6 +1,63 @@
++import { ESLint, Linter, Rule } from "eslint";
++
+ /** @deprecated */
+ export const builtinRules: Map<string, import("./index.js").Rule.RuleModule>;
+ /** @deprecated */
++export namespace FlatESLint {
++    interface Options {
++        // File enumeration
++        cwd?: string | undefined;
++        errorOnUnmatchedPattern?: boolean | undefined;
++        globInputPaths?: boolean | undefined;
++        ignore?: boolean | undefined;
++
++        // Linting
++        allowInlineConfig?: boolean | undefined;
++        baseConfig?: Linter.FlatConfig | Linter.FlatConfig[] | undefined;
++        overrideConfig?: Linter.FlatConfig | Linter.FlatConfig[] | undefined;
++        overrideConfigFile?: boolean | string | undefined;
++        reportUnusedDisableDirectives?: Linter.StringSeverity | undefined;
++
++        // Autofix
++        fix?: boolean | ((message: Linter.LintMessage) => boolean) | undefined;
++        fixTypes?: Rule.RuleMetaData['type'][] | undefined;
++
++        // Cache-related
++        cache?: boolean | undefined;
++        cacheLocation?: string | undefined;
++        cacheStrategy?: 'content' | 'metadata' | undefined;
++    }
++}
++/** @deprecated */
++export class FlatESLint {
++    constructor(options?: FlatESLint.Options);
++
++    static get version(): string;
++
++    static outputFixes(results: ESLint.LintResult[]): Promise<void>;
++
++    static getErrorResults(results: ESLint.LintResult[]): ESLint.LintResult[];
++
++    getRulesMetaForResults(results: ESLint.LintResult[]): Record<string, Rule.RuleMetaData>;
++
++    lintFiles(patterns: string | string[]): Promise<ESLint.LintResult[]>;
++
++    lintText(
++      code: string,
++      options?: { filePath?: string | undefined; warnIgnored?: boolean | undefined },
++    ): Promise<ESLint.LintResult[]>;
++
++    loadFormatter(name?: string): Promise<ESLint.Formatter>;
++
++    calculateConfigForFile(filePath: string): Promise<Linter.FlatConfig | undefined>;
++
++    findConfigFile(): Promise<string | undefined>;
++
++    isPathIgnored(filePath: string): Promise<boolean>;
++}
++/** @deprecated */
++export function shouldUseFlatConfig(): Promise<boolean>;
++/** @deprecated */
+ export class FileEnumerator {
+     constructor(
+         params?: {
+@@ -17,3 +74,7 @@ export class FileEnumerator {
+         patternOrPatterns: string | string[],
+     ): IterableIterator<{ config: any; filePath: string; ignored: boolean }>;
+ }
++export {
++    /** @deprecated */
++    ESLint as LegacyESLint
++};

src/cli/run.ts

@@ -3,6 +3,7 @@ import { fileURLToPath } from 'node:url';
 import { Worker } from 'node:worker_threads';
 import { wrap } from 'comlink';
 import nodeEndpoint from 'comlink/dist/esm/node-adapter.mjs';
+import eslintPkg from 'eslint/use-at-your-own-risk';
 import isInstalledGlobally from 'is-installed-globally';
 import terminalLink from 'terminal-link';
 import { warn } from '../cli/log.js';
@@ -11,6 +12,8 @@ import { translateCLIOptions } from '../config.js';
 import { SerializableCore } from '../core-worker.js';
 import { lint, selectAction, selectRuleIds, checkResults, NextScene } from '../scene/index.js';
 
+const { shouldUseFlatConfig } = eslintPkg;
+
 export type Options = {
   argv: string[];
 };
@@ -27,6 +30,10 @@ export async function run(options: Options) {
     );
   }
   const parsedCLIOptions = parseArgv(options.argv);
+  const usingFlatConfig = await shouldUseFlatConfig();
+  if (usingFlatConfig) {
+    throw new Error('Flat Config is not yet supported.'); // TODO: support flat config
+  }
   const config = translateCLIOptions(parsedCLIOptions, 'eslintrc'); // TODO: support flat config
 
   // Directly executing the Core API will hog the main thread and halt the spinner.

src/config.ts

@@ -1,8 +1,8 @@
-import { ESLint } from 'eslint';
+import type { LegacyESLint } from 'eslint/use-at-your-own-risk';
 import { cliOptionsDefaults, ParsedCLIOptions } from './cli/parse-argv.js';
 import { DeepPartial } from './util/type-check.js';
-type ESLintrcESLintOptions = { type: 'eslintrc' } & Pick<
-  ESLint.Options,
+type LegacyESLintOptions = { type: 'eslintrc' } & Pick<
+  LegacyESLint.Options,
   | 'useEslintrc'
   | 'overrideConfigFile'
   | 'extensions'
@@ -15,7 +15,7 @@ type ESLintrcESLintOptions = { type: 'eslintrc' } & Pick<
   | 'resolvePluginsRelativeTo'
 >;
 
-export type ESLintOptions = ESLintrcESLintOptions; // TODO: support flat config
+export type ESLintOptions = LegacyESLintOptions; // TODO: support flat config
 
 /** The config of eslint-interactive */
 export type Config = {

src/core.test.ts

@@ -3,11 +3,14 @@ import { dirname, join, relative } from 'node:path';
 import { fileURLToPath } from 'node:url';
 import dedent from 'dedent';
 import { ESLint, Linter } from 'eslint';
+import eslintPkg from 'eslint/use-at-your-own-risk';
 import { resolve } from 'import-meta-resolve';
 import { beforeEach, describe, expect, test, vi } from 'vitest';
 import { Core } from './core.js';
 import { createIFF } from './test-util/fixtures.js';
 
+const { LegacyESLint } = eslintPkg;
+
 const rootDir = join(dirname(fileURLToPath(import.meta.url)), '..');
 
 // Normalize `message` for the snapshot.
@@ -181,7 +184,7 @@ describe('Core', () => {
   });
   test('printSummaryOfResults', async () => {
     const results = await core.lint();
-    vi.spyOn(ESLint.prototype, 'getRulesMetaForResults').mockImplementationOnce(() => {
+    vi.spyOn(LegacyESLint.prototype, 'getRulesMetaForResults').mockImplementationOnce(() => {
       return {
         'prefer-const': {
           docs: {