From f55dc1b55ea84bfb4752ffdff5fbf1da6575f131 Mon Sep 17 00:00:00 2001
From: Lars Kappert <lars@webpro.nl>
Date: Tue, 25 Feb 2025 07:06:51 +0100
Subject: [PATCH] Add support for eslint v9 config files + settings

---
 .../fixtures/plugins/eslint2/eslint.config.ts | 19 ++++++++
 .../knip/fixtures/plugins/eslint2/knip.json   |  3 ++
 .../eslint2/node_modules/@eslint/js/index.js  |  6 +++
 .../node_modules/@eslint/js/package.json      |  3 ++
 .../index.js                                  |  0
 .../package.json                              |  3 ++
 .../eslint2/node_modules/eslint/index.js      |  3 ++
 .../eslint2/node_modules/eslint/package.json  |  4 ++
 .../node_modules/typescript-eslint/index.js   | 43 +++++++++++++++++++
 .../typescript-eslint/package.json            |  9 ++++
 .../fixtures/plugins/eslint2/package.json     | 12 ++++++
 packages/knip/src/plugins/eslint/helpers.ts   | 35 +++++++++++----
 packages/knip/src/plugins/eslint/index.ts     | 28 +++++++++---
 packages/knip/src/plugins/eslint/types.ts     |  8 ++--
 packages/knip/src/plugins/xo/index.ts         |  4 +-
 packages/knip/src/plugins/xo/types.ts         |  4 +-
 packages/knip/test/plugins/eslint2.test.ts    | 21 +++++++++
 17 files changed, 184 insertions(+), 21 deletions(-)
 create mode 100644 packages/knip/fixtures/plugins/eslint2/eslint.config.ts
 create mode 100644 packages/knip/fixtures/plugins/eslint2/knip.json
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/index.js
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/package.json
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/index.js
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/package.json
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/eslint/index.js
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/eslint/package.json
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/index.js
 create mode 100644 packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/package.json
 create mode 100644 packages/knip/fixtures/plugins/eslint2/package.json
 create mode 100644 packages/knip/test/plugins/eslint2.test.ts

diff --git a/packages/knip/fixtures/plugins/eslint2/eslint.config.ts b/packages/knip/fixtures/plugins/eslint2/eslint.config.ts
new file mode 100644
index 000000000..f86448531
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/eslint.config.ts
@@ -0,0 +1,19 @@
+import eslint from '@eslint/js';
+import tseslint from 'typescript-eslint';
+
+export default [
+  ...tseslint.config(eslint.configs.recommended, tseslint.configs.recommended),
+  {
+    files: ['**/*.{ts,tsx}'],
+    settings: {
+      'import/parsers': {
+        '@typescript-eslint/parser': ['.ts', '.tsx'],
+      },
+      'import/resolver': {
+        typescript: true,
+        node: true,
+      },
+    },
+    rules: {},
+  },
+];
diff --git a/packages/knip/fixtures/plugins/eslint2/knip.json b/packages/knip/fixtures/plugins/eslint2/knip.json
new file mode 100644
index 000000000..af29f9e74
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/knip.json
@@ -0,0 +1,3 @@
+{
+  "eslint": ["eslint.config.ts"]
+}
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/index.js b/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/index.js
new file mode 100644
index 000000000..8f5f8520e
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/index.js
@@ -0,0 +1,6 @@
+module.exports = {
+  configs: {
+    all: [],
+    recommended: [],
+  },
+};
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/package.json b/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/package.json
new file mode 100644
index 000000000..05e8955ed
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/@eslint/js/package.json
@@ -0,0 +1,3 @@
+{
+  "name": "@eslint/js"
+}
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/index.js b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/index.js
new file mode 100644
index 000000000..e69de29bb
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/package.json b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/package.json
new file mode 100644
index 000000000..0b5d6530c
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint-import-resolver-typescript/package.json
@@ -0,0 +1,3 @@
+{
+  "name": "eslint-import-resolver-typescript"
+}
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/index.js b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/index.js
new file mode 100644
index 000000000..b2dc471f8
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/index.js
@@ -0,0 +1,3 @@
+module.exports = {
+  Linter,
+};
\ No newline at end of file
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/package.json b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/package.json
new file mode 100644
index 000000000..2877896f0
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/eslint/package.json
@@ -0,0 +1,4 @@
+{
+  "name": "eslint",
+  "bin": "index.js"
+}
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/index.js b/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/index.js
new file mode 100644
index 000000000..759743b2a
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/index.js
@@ -0,0 +1,43 @@
+Object.defineProperty(exports, '__esModule', { value: true });
+exports.config = exports.configs = exports.plugin = exports.parser = void 0;
+
+const parserBase = { parseForESLint: () => {} };
+const config_helper_1 = {
+  config: (...args) => {
+    return [
+      {
+        rules: {},
+      },
+      {
+        name: 'typescript-eslint/base',
+        languageOptions: { parser: [], sourceType: 'module' },
+        plugins: { '@typescript-eslint': [] },
+      },
+      {
+        files: ['**/*.ts', '**/*.tsx', '**/*.mts', '**/*.cts'],
+        rules: {},
+        name: 'typescript-eslint/eslint-recommended',
+      },
+      {
+        name: 'typescript-eslint/recommended',
+        rules: {},
+      },
+    ];
+  },
+};
+
+exports.parser = {
+  meta: parserBase.meta,
+  parseForESLint: parserBase.parseForESLint,
+};
+
+exports.configs = {
+  recommended: [],
+};
+
+exports.default = {
+  config: config_helper_1.config,
+  configs: exports.configs,
+  parser: exports.parser,
+  plugin: exports.plugin,
+};
diff --git a/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/package.json b/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/package.json
new file mode 100644
index 000000000..09abf1942
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/node_modules/typescript-eslint/package.json
@@ -0,0 +1,9 @@
+{
+  "name": "typescript-eslint",
+  "type": "commonjs",
+  "exports": {
+    ".": {
+      "default": "./index.js"
+    }
+  }
+}
diff --git a/packages/knip/fixtures/plugins/eslint2/package.json b/packages/knip/fixtures/plugins/eslint2/package.json
new file mode 100644
index 000000000..eda154346
--- /dev/null
+++ b/packages/knip/fixtures/plugins/eslint2/package.json
@@ -0,0 +1,12 @@
+{
+  "name": "@fixtures/eslint2",
+  "scripts": {
+    "lint": "eslint"
+  },
+  "devDependencies": {
+    "@eslint/js": "*",
+    "eslint": "*",
+    "eslint-import-resolver-typescript": "*",
+    "typescript-eslint": "*"
+  }
+}
diff --git a/packages/knip/src/plugins/eslint/helpers.ts b/packages/knip/src/plugins/eslint/helpers.ts
index 5ab98ae05..743d63b3e 100644
--- a/packages/knip/src/plugins/eslint/helpers.ts
+++ b/packages/knip/src/plugins/eslint/helpers.ts
@@ -2,12 +2,29 @@ import type { PluginOptions } from '../../types/config.js';
 import { compact } from '../../util/array.js';
 import { type ConfigInput, type Input, toConfig, toDeferResolve } from '../../util/input.js';
 import { getPackageNameFromFilePath, getPackageNameFromModuleSpecifier } from '../../util/modules.js';
-import { isAbsolute, isInternal } from '../../util/path.js';
+import { extname, isAbsolute, isInternal } from '../../util/path.js';
 import { getDependenciesFromConfig } from '../babel/index.js';
-import type { ESLintConfig, OverrideConfig } from './types.js';
+import type { ESLintConfig, ESLintConfigDeprecated, OverrideConfigDeprecated } from './types.js';
 
-export const getDependencies = (
-  config: ESLintConfig | OverrideConfig,
+export const getInputs = (
+  config: ESLintConfigDeprecated | OverrideConfigDeprecated | ESLintConfig,
+  options: PluginOptions
+): (Input | ConfigInput)[] => {
+  const { configFileName } = options;
+
+  if (extname(configFileName) === '.json' || !/eslint\.config/.test(configFileName)) {
+    return getInputsDeprecated(config as ESLintConfigDeprecated | OverrideConfigDeprecated, options);
+  }
+
+  const dependencies = (config as ESLintConfig).flatMap(config =>
+    config.settings ? getDependenciesFromSettings(config.settings).filter(id => id !== '@typescript-eslint/parser') : []
+  );
+
+  return compact(dependencies).map(id => toDeferResolve(id));
+};
+
+const getInputsDeprecated = (
+  config: ESLintConfigDeprecated | OverrideConfigDeprecated,
   options: PluginOptions
 ): (Input | ConfigInput)[] => {
   const extendsSpecifiers = config.extends ? compact([config.extends].flat().map(resolveExtendSpecifier)) : [];
@@ -25,9 +42,9 @@ export const getDependencies = (
   const settings = config.settings ? getDependenciesFromSettings(config.settings) : [];
   // const rules = getDependenciesFromRules(config.rules); // TODO enable in next major? Unexpected/breaking in certain cases w/ eslint v8
   const rules = getDependenciesFromRules({});
-  const overrides = config.overrides ? [config.overrides].flat().flatMap(d => getDependencies(d, options)) : [];
-  const x = compact([...extendsSpecifiers, ...plugins, parser, ...settings, ...rules]).map(toDeferResolve);
-  return [...extendConfigs, ...x, ...babelDependencies, ...overrides];
+  const overrides = config.overrides ? [config.overrides].flat().flatMap(d => getInputsDeprecated(d, options)) : [];
+  const deferred = compact([...extendsSpecifiers, ...plugins, parser, ...settings, ...rules]).map(toDeferResolve);
+  return [...extendConfigs, ...deferred, ...babelDependencies, ...overrides];
 };
 
 const isQualifiedSpecifier = (specifier: string) =>
@@ -59,12 +76,12 @@ const resolveExtendSpecifier = (specifier: string) => {
   return resolveSpecifier(namespace, specifier);
 };
 
-const getDependenciesFromRules = (rules: ESLintConfig['rules'] = {}) =>
+const getDependenciesFromRules = (rules: ESLintConfigDeprecated['rules'] = {}) =>
   Object.keys(rules).flatMap(ruleKey =>
     ruleKey.includes('/') ? [resolveSpecifier('eslint-plugin', ruleKey.split('/').slice(0, -1).join('/'))] : []
   );
 
-const getDependenciesFromSettings = (settings: ESLintConfig['settings'] = {}) => {
+const getDependenciesFromSettings = (settings: ESLintConfigDeprecated['settings'] = {}) => {
   return Object.entries(settings).flatMap(([settingKey, settings]) => {
     if (settingKey === 'import/resolver') {
       return (typeof settings === 'string' ? [settings] : Object.keys(settings))
diff --git a/packages/knip/src/plugins/eslint/index.ts b/packages/knip/src/plugins/eslint/index.ts
index 994f2957c..5db6e15ba 100644
--- a/packages/knip/src/plugins/eslint/index.ts
+++ b/packages/knip/src/plugins/eslint/index.ts
@@ -1,7 +1,7 @@
 import type { IsPluginEnabled, Plugin, ResolveConfig } from '../../types/config.js';
 import { hasDependency } from '../../util/plugin.js';
-import { getDependencies } from './helpers.js';
-import type { ESLintConfig } from './types.js';
+import { getInputs } from './helpers.js';
+import type { ESLintConfigDeprecated } from './types.js';
 
 // New: https://eslint.org/docs/latest/use/configure/configuration-files
 // Old: https://eslint.org/docs/latest/use/configure/configuration-files-deprecated
@@ -24,10 +24,28 @@ const entry = ['eslint.config.{js,cjs,mjs,ts,cts,mts}'];
 
 const config = ['.eslintrc', '.eslintrc.{js,json,cjs}', '.eslintrc.{yml,yaml}', 'package.json'];
 
-const resolveConfig: ResolveConfig<ESLintConfig> = (localConfig, options) => getDependencies(localConfig, options);
+const resolveConfig: ResolveConfig<ESLintConfigDeprecated> = (localConfig, options) => getInputs(localConfig, options);
 
-const note = `For ESLint v8 users: if relying on [configuration cascading](https://eslint.org/docs/v8.x/use/configure/configuration-files#cascading-and-hierarchy),
-consider using something like this:
+const note = `### ESLint v9
+
+Only regular \`import\` statements are considered by default.
+The configuration object is not resolved to find dependencies for \`settings\` such as \`"eslint-import-resolver-typescript"\`.
+To enable this, lift the \`entry\` to a \`config\` file like so:
+
+\`\`\`json
+{
+  "eslint": ["eslint.config.ts"]
+}
+\`\`\`
+
+This is not enabled by default, since this exception may be thrown by a \`@rushstack/eslint-*\` package:
+
+> \`Error: Failed to patch ESLint because the calling module was not recognized.\`
+
+### ESLint v8
+
+If relying on [configuration cascading](https://eslint.org/docs/v8.x/use/configure/configuration-files#cascading-and-hierarchy),
+consider using an extended glob pattern like this:
 
 \`\`\`json
 {
diff --git a/packages/knip/src/plugins/eslint/types.ts b/packages/knip/src/plugins/eslint/types.ts
index 21fb0627a..8481d4f3e 100644
--- a/packages/knip/src/plugins/eslint/types.ts
+++ b/packages/knip/src/plugins/eslint/types.ts
@@ -21,9 +21,11 @@ type BaseConfig = {
   rules?: Rules;
 };
 
-export type OverrideConfig = BaseConfig & { files: string[]; overrides: OverrideConfig };
+export type ESLintConfig = BaseConfig[];
 
-export type ESLintConfig = BaseConfig & {
+export type OverrideConfigDeprecated = BaseConfig & { files: string[]; overrides: OverrideConfigDeprecated };
+
+export type ESLintConfigDeprecated = BaseConfig & {
   env?: Record<string, boolean>;
-  overrides?: OverrideConfig[];
+  overrides?: OverrideConfigDeprecated[];
 };
diff --git a/packages/knip/src/plugins/xo/index.ts b/packages/knip/src/plugins/xo/index.ts
index 9a7c7be12..76fa2b207 100644
--- a/packages/knip/src/plugins/xo/index.ts
+++ b/packages/knip/src/plugins/xo/index.ts
@@ -1,6 +1,6 @@
 import type { IsPluginEnabled, Plugin, ResolveConfig } from '../../types/config.js';
 import { hasDependency } from '../../util/plugin.js';
-import { getDependencies } from '../eslint/helpers.js';
+import { getInputs } from '../eslint/helpers.js';
 import type { XOConfig } from './types.js';
 
 // https://github.com/xojs/xo#config
@@ -18,7 +18,7 @@ const config = ['package.json', '.xo-config', '.xo-config.{js,cjs,json}', 'xo.co
 const entry = ['.xo-config.{js,cjs}', 'xo.config.{js,cjs}'];
 
 const resolveConfig: ResolveConfig<XOConfig> = async (config, options) => {
-  const inputs = getDependencies(config, options);
+  const inputs = getInputs(config, options);
   return [...inputs];
 };
 
diff --git a/packages/knip/src/plugins/xo/types.ts b/packages/knip/src/plugins/xo/types.ts
index 8b89ac814..2753c9b74 100644
--- a/packages/knip/src/plugins/xo/types.ts
+++ b/packages/knip/src/plugins/xo/types.ts
@@ -1,6 +1,6 @@
-import type { ESLintConfig } from '../eslint/types.js';
+import type { ESLintConfigDeprecated } from '../eslint/types.js';
 
-export type XOConfig = ESLintConfig & {
+export type XOConfig = ESLintConfigDeprecated & {
   envs?: string[] | undefined;
   globals?: string[] | undefined;
   ignores?: string[] | undefined;
diff --git a/packages/knip/test/plugins/eslint2.test.ts b/packages/knip/test/plugins/eslint2.test.ts
new file mode 100644
index 000000000..557fc02ae
--- /dev/null
+++ b/packages/knip/test/plugins/eslint2.test.ts
@@ -0,0 +1,21 @@
+import { test } from 'bun:test';
+import assert from 'node:assert/strict';
+import { main } from '../../src/index.js';
+import { resolve } from '../../src/util/path.js';
+import baseArguments from '../helpers/baseArguments.js';
+import baseCounters from '../helpers/baseCounters.js';
+
+const cwd = resolve('fixtures/plugins/eslint2');
+
+test('Find dependencies with the ESLint plugin (2)', async () => {
+  const { counters } = await main({
+    ...baseArguments,
+    cwd,
+  });
+
+  assert.deepEqual(counters, {
+    ...baseCounters,
+    processed: 1,
+    total: 1,
+  });
+});