Fix typescript only rules are being checked against pure js files

jest.config.js

@@ -1,4 +1,5 @@
 module.exports = {
+    globalSetup: '<rootDir>/jest.globalSetup.js',
     transform: {
         '^.+\\.ts$': 'ts-jest',
     },

jest.globalSetup.js

@@ -0,0 +1,11 @@
+const {execFileSync} = require('node:child_process');
+const path = require('node:path');
+
+module.exports = function globalSetup() {
+  // Build the bundle once for the whole test run so tests that exercise the
+  // published artifact can require it without each rebuilding it themselves.
+  execFileSync('npm', ['run', 'build'], {
+    cwd: path.resolve(__dirname),
+    stdio: 'pipe',
+  });
+};

src/bundle.test.ts

@@ -5,18 +5,9 @@ import {execFileSync} from 'node:child_process';
 
 const requireFromTest = createRequire(__filename);
 
-function buildBundle(): string {
-    execFileSync('npm', ['run', 'build'], {
-        cwd: path.resolve(__dirname, '..'),
-        stdio: 'pipe',
-    });
-
-    return path.resolve(__dirname, '../dist/index.cjs');
-}
-
 describe('published bundle', () => {
     it('inlines metadata for bundled plugins that read their own package.json', () => {
-        const bundlePath = buildBundle();
+        const bundlePath = path.resolve(__dirname, '../dist/index.cjs');
         const bundle = fs.readFileSync(bundlePath, 'utf8');
 
         expect(bundle).not.toContain('cjsRequire("../package.json")');

src/configs/typescript.test.ts

@@ -0,0 +1,36 @@
+import path from 'node:path';
+import {execFileSync} from 'node:child_process';
+
+const bundlePath = path.resolve(__dirname, '../../dist/index.cjs');
+
+function lint(filename: string, code: string): Array<{ruleId: string | null, message: string}> {
+    const script = `
+        const {Linter} = require('eslint');
+        const {configs} = require(${JSON.stringify(bundlePath)});
+        const messages = new Linter().verify(
+            ${JSON.stringify(code)},
+            configs.typescript,
+            {filename: ${JSON.stringify(filename)}},
+        );
+        process.stdout.write(JSON.stringify(messages));
+    `;
+
+    const output = execFileSync('node', ['-e', script], {
+        cwd: path.resolve(__dirname, '../..'),
+        encoding: 'utf8',
+    });
+
+    return JSON.parse(output) as Array<{ruleId: string | null, message: string}>;
+}
+
+describe('typescript', () => {
+    it('should not apply type-checked rules to pure JS files', () => {
+        const messages = lint('file.js', 'const x = 1;\n');
+
+        const typeAwareErrors = messages.filter(
+            message => message.message.includes('requires type information'),
+        );
+
+        expect(typeAwareErrors).toEqual([]);
+    });
+});

src/configs/typescript.ts

@@ -90,15 +90,24 @@ const baseRules: Linter.RulesRecord = {
     'no-void': 'off',
 };
 
+const typescriptFiles = ['**/*.ts', '**/*.tsx', '**/*.mts', '**/*.cts'];
+
 // Factory function to create TypeScript config with the plugin reference
 export function createTypescriptConfig(plugin: ESLint.Plugin, javascriptConfig: Linter.Config[]): Linter.Config[] {
     return [
         ...javascriptConfig,
-        ...tseslint.configs.recommendedTypeChecked,
+        ...tseslint.configs
+            .recommendedTypeChecked
+            .map(
+                config => ({
+                    ...config,
+                    files: typescriptFiles,
+                }),
+            ),
         jest.configs['flat/recommended'],
         {
             name: '@croct/typescript',
-            files: ['**/*.ts', '**/*.tsx'],
+            files: typescriptFiles,
             plugins: {
                 '@stylistic': stylistic,
                 '@croct': plugin,