Improve support for flat config in eslint plugin (resolves #806)

packages/knip/src/plugins/eslint/helpers.ts

@@ -2,12 +2,33 @@ 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 inputs = (config as ESLintConfig).flatMap(config => {
+    const settings = config.settings
+      ? getDependenciesFromSettings(config.settings).filter(id => id !== '@typescript-eslint/parser')
+      : [];
+
+    return compact([...settings]).map(d => toDeferResolve(d));
+  });
+
+  return inputs;
+};
+
+const getInputsDeprecated = (
+  config: ESLintConfigDeprecated | OverrideConfigDeprecated,
   options: PluginOptions
 ): (Input | ConfigInput)[] => {
   const extendsSpecifiers = config.extends ? compact([config.extends].flat().map(resolveExtendSpecifier)) : [];
@@ -23,9 +44,9 @@ 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) =>
@@ -57,12 +78,12 @@ 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))

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
@@ -20,18 +20,21 @@ const isEnabled: IsPluginEnabled = ({ dependencies, manifest, config }) =>
 
 const packageJsonPath = 'eslintConfig';
 
-const entry = ['eslint.config.{js,cjs,mjs}'];
+const config = [
+  'eslint.config.{js,cjs,mjs,ts,mts,cts}',
+  '.eslintrc',
+  '.eslintrc.{js,json,cjs}',
+  '.eslintrc.{yml,yaml}',
+  'package.json',
+];
 
-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);
 
 export default {
   title,
   enablers,
   isEnabled,
   packageJsonPath,
-  entry,
   config,
   resolveConfig,
 } satisfies Plugin;

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[];
 };

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';
 
 // link to xo docs: https://github.com/xojs/xo#config
@@ -20,7 +20,7 @@ const config = ['package.json', '.xo-config', '.xo-config.{js,cjs,json}', 'xo.co
 const entry: string[] = ['.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];
 };
 

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;