[Fix] no-unused-modules`: don't error out when running with flat config and an eslintrc isn't present

This change adjusts what we're doing if an error is thrown while attempting to enumerate lintable files in the no-used-modules rule, when users are running with flat config. Now, if FileEnumerator throws due to a lack of eslintrc and the user is running with flat config, we catch the error and rethrow with a more informative message.

I also cleaned up the original aspects of the implementation that was using the proposed eslint context functions, since that proposal was walked back and the API was never introduced.

Note: This isn't an ideal state, since this rule still relies on the legacy api to understand what needs to be ignored. Remaining tethered to the legacy config system is going to need to be solved at some point.

Fixes #3079

Author: michaelfaith

CHANGELOG.md

@@ -10,6 +10,9 @@ This change log adheres to standards from [Keep a CHANGELOG](https://keepachange
 - add [`enforce-node-protocol-usage`] rule and `import/node-version` setting ([#3024], thanks [@GoldStrikeArch] and [@sevenc-nanashi])
 - add TypeScript types ([#3097], thanks [@G-Rath])
 
+### Fixed
+- [`no-unused-modules`]: don't error out when running with flat config and an eslintrc isn't present ([#3116], thanks [@michaelfaith])
+
 ### Changed
 - [Docs] [`extensions`], [`order`]: improve documentation ([#3106], thanks [@Xunnamius])
 
@@ -1161,6 +1164,7 @@ for info on changes for earlier releases.
 
 [`memo-parser`]: ./memo-parser/README.md
 
+[#3116]: https://github.com/import-js/eslint-plugin-import/pull/3116
 [#3106]: https://github.com/import-js/eslint-plugin-import/pull/3106
 [#3097]: https://github.com/import-js/eslint-plugin-import/pull/3097
 [#3073]: https://github.com/import-js/eslint-plugin-import/pull/3073

examples/flat/package.json

@@ -12,6 +12,7 @@
     "cross-env": "^7.0.3",
     "eslint": "^8.57.0",
     "eslint-plugin-import": "file:../..",
+    "move-file-cli": "^3.0.0",
     "typescript": "^5.4.5"
   }
 }

examples/v9/eslint.config.mjs

@@ -0,0 +1,26 @@
+import importPlugin from 'eslint-plugin-import';
+import js from '@eslint/js';
+import tsParser from '@typescript-eslint/parser';
+
+export default [
+  js.configs.recommended,
+  importPlugin.flatConfigs.recommended,
+  importPlugin.flatConfigs.react,
+  importPlugin.flatConfigs.typescript,
+  {
+    files: ['**/*.{js,mjs,cjs,jsx,mjsx,ts,tsx,mtsx}'],
+    languageOptions: {
+      parser: tsParser,
+      ecmaVersion: 'latest',
+      sourceType: 'module',
+    },
+    ignores: ['eslint.config.mjs', '**/exports-unused.ts'],
+    rules: {
+      'no-unused-vars': 'off',
+      'import/no-dynamic-require': 'warn',
+      'import/no-nodejs-modules': 'warn',
+      'import/no-unused-modules': ['warn', { unusedExports: true }],
+      'import/no-cycle': 'warn',
+    },
+  },
+];

examples/v9/package.json

@@ -0,0 +1,18 @@
+{
+  "name": "v9",
+  "version": "1.0.0",
+  "main": "index.js",
+  "scripts": {
+    "lint": "eslint src --report-unused-disable-directives"
+  },
+  "devDependencies": {
+    "@eslint/js": "^9.17.0",
+    "@types/node": "^20.14.5",
+    "@typescript-eslint/parser": "^8.18.0",
+    "cross-env": "^7.0.3",
+    "eslint": "^9.17.0",
+    "eslint-plugin-import": "file:../..",
+    "move-file-cli": "^3.0.0",
+    "typescript": "^5.4.5"
+  }
+}

examples/v9/src/depth-zero.js

@@ -0,0 +1,3 @@
+import { foo } from "./es6/depth-one-dynamic";
+
+foo();

examples/v9/src/es6/depth-one-dynamic.js

@@ -0,0 +1,3 @@
+export function foo() {}
+
+export const bar = () => import("../depth-zero").then(({foo}) => foo);

examples/v9/src/exports-unused.ts

@@ -0,0 +1,12 @@
+export type ScalarType = string | number;
+export type ObjType = {
+  a: ScalarType;
+  b: ScalarType;
+};
+
+export const a = 13;
+export const b = 18;
+
+const defaultExport: ObjType = { a, b };
+
+export default defaultExport;

examples/v9/src/exports.ts

@@ -0,0 +1,12 @@
+export type ScalarType = string | number;
+export type ObjType = {
+  a: ScalarType;
+  b: ScalarType;
+};
+
+export const a = 13;
+export const b = 18;
+
+const defaultExport: ObjType = { a, b };
+
+export default defaultExport;

examples/v9/src/imports.ts

@@ -0,0 +1,7 @@
+//import c from './exports';
+import { a, b } from './exports';
+import type { ScalarType, ObjType } from './exports';
+
+import path from 'path';
+import fs from 'node:fs';
+import console from 'console';

examples/v9/src/jsx.tsx

@@ -0,0 +1,3 @@
+const Components = () => {
+  return <></>;
+};