feat(core): Add ESM support for Eslint config file (#29613)

This pull request includes changes to migrate ESLint configuration files
from CommonJS (`.cjs`) to ECMAScript modules (`.mjs`) as the default.

### ESLint Configuration Generation Changes

The changes also ensure consistent generated eslint configs based on the
base eslint config.
- If the workspace root has an `eslint.config.cjs` or `eslint.config.js`
with `module.exports`. When you create a library or application it will
generate an accompanying config at path
`{projectRoot}/eslint.config.cjs` of the same format.
- If the workspace root has an `eslint.config.mjs` or
`eslint.config.mjs` with `export default`. When you create a library or
application it will generate an accompanying config at path
`{projectRoot}/eslint.config.mjs`.
- If no eslint config is found at the workspace root one will be created
`eslint.config.mjs`

Author: ndcunningham

e2e/angular/src/misc.test.ts

@@ -39,7 +39,7 @@ describe('Move Angular Project', () => {
     expect(moveOutput).toContain(`CREATE ${newPath}/tsconfig.app.json`);
     expect(moveOutput).toContain(`CREATE ${newPath}/tsconfig.json`);
     expect(moveOutput).toContain(`CREATE ${newPath}/tsconfig.spec.json`);
-    expect(moveOutput).toContain(`CREATE ${newPath}/eslint.config.cjs`);
+    expect(moveOutput).toContain(`CREATE ${newPath}/eslint.config.mjs`);
     expect(moveOutput).toContain(`CREATE ${newPath}/public/favicon.ico`);
     expect(moveOutput).toContain(`CREATE ${newPath}/src/index.html`);
     expect(moveOutput).toContain(`CREATE ${newPath}/src/main.ts`);

e2e/angular/src/projects.test.ts

@@ -164,13 +164,13 @@ describe('Angular Projects', () => {
 
   it('should lint correctly with eslint and handle external HTML files and inline templates', async () => {
     // disable the prefer-standalone rule for app1 which is not standalone
-    let app1EslintConfig = readFile(`${app1}/eslint.config.cjs`);
+    let app1EslintConfig = readFile(`${app1}/eslint.config.mjs`);
     app1EslintConfig = app1EslintConfig.replace(
       `'@angular-eslint/directive-selector': [`,
       `'@angular-eslint/prefer-standalone': 'off',
       '@angular-eslint/directive-selector': [`
     );
-    updateFile(`${app1}/eslint.config.cjs`, app1EslintConfig);
+    updateFile(`${app1}/eslint.config.mjs`, app1EslintConfig);
 
     // check apps and lib pass linting for initial generated code
     runCLI(`run-many --target lint --projects=${app1},${lib1} --parallel`);

e2e/eslint/src/linter-legacy.test.ts

@@ -150,10 +150,10 @@ describe('Linter (legacy)', () => {
         env: { NX_ADD_PLUGINS: 'false' },
       });
       checkFilesExist(
-        'eslint.config.cjs',
-        `apps/${myapp}/eslint.config.cjs`,
-        `libs/${mylib}/eslint.config.cjs`,
-        `libs/${mylib2}/eslint.config.cjs`
+        'eslint.config.mjs',
+        `apps/${myapp}/eslint.config.mjs`,
+        `libs/${mylib}/eslint.config.mjs`,
+        `libs/${mylib2}/eslint.config.mjs`
       );
       checkFilesDoNotExist(
         '.eslintrc.json',
@@ -164,12 +164,12 @@ describe('Linter (legacy)', () => {
 
       // move eslint.config one step up
       // to test the absence of the flat eslint config in the project root folder
-      renameFile(`libs/${mylib2}/eslint.config.cjs`, `libs/eslint.config.cjs`);
+      renameFile(`libs/${mylib2}/eslint.config.mjs`, `libs/eslint.config.mjs`);
       updateFile(
-        `libs/eslint.config.cjs`,
-        readFile(`libs/eslint.config.cjs`).replace(
-          `../../eslint.config.cjs`,
-          `../eslint.config.cjs`
+        `libs/eslint.config.mjs`,
+        readFile(`libs/eslint.config.mjs`).replace(
+          `../../eslint.config.mjs`,
+          `../eslint.config.mjs`
         )
       );
 
@@ -202,9 +202,9 @@ describe('Linter (legacy)', () => {
         env: { NX_ADD_PLUGINS: 'false' },
       });
       checkFilesExist(
-        'eslint.config.cjs',
-        `${mylib}/eslint.config.cjs`,
-        'eslint.base.config.cjs'
+        'eslint.config.mjs',
+        `${mylib}/eslint.config.mjs`,
+        'eslint.base.config.mjs'
       );
       checkFilesDoNotExist(
         '.eslintrc.json',

e2e/eslint/src/linter.test.ts

@@ -615,8 +615,8 @@ describe('Linter', () => {
         runCLI(`generate @nx/js:lib ${jsLib} --linter eslint`);
 
         checkFilesExist(
-          `${reactLib}/eslint.config.cjs`,
-          `${jsLib}/eslint.config.cjs`
+          `${reactLib}/eslint.config.mjs`,
+          `${jsLib}/eslint.config.mjs`
         );
         checkFilesDoNotExist(
           `${reactLib}/.eslintrc.json`,

e2e/nx/src/__snapshots__/extras.test.ts.snap

@@ -26,7 +26,7 @@ exports[`Extra Nx Misc Tests task graph inputs should correctly expand dependent
   ],
   "lib-base-123": [
     "libs/lib-base-123/README.md",
-    "libs/lib-base-123/eslint.config.cjs",
+    "libs/lib-base-123/eslint.config.mjs",
     "libs/lib-base-123/jest.config.ts",
     "libs/lib-base-123/package.json",
     "libs/lib-base-123/project.json",
@@ -39,7 +39,7 @@ exports[`Extra Nx Misc Tests task graph inputs should correctly expand dependent
   ],
   "lib-dependent-123": [
     "libs/lib-dependent-123/README.md",
-    "libs/lib-dependent-123/eslint.config.cjs",
+    "libs/lib-dependent-123/eslint.config.mjs",
     "libs/lib-dependent-123/jest.config.ts",
     "libs/lib-dependent-123/package.json",
     "libs/lib-dependent-123/project.json",

packages/angular/src/generators/ng-add/__snapshots__/migrate-from-angular-cli.spec.ts.snap

@@ -94,6 +94,7 @@ exports[`workspace move to nx layout should create nx.json 1`] = `
       "!{projectRoot}/karma.conf.js",
       "!{projectRoot}/.eslintrc.json",
       "!{projectRoot}/eslint.config.cjs",
+      "!{projectRoot}/eslint.config.mjs",
     ],
     "sharedGlobals": [],
   },
@@ -104,7 +105,7 @@ exports[`workspace move to nx layout should create nx.json 1`] = `
         "default",
         "{workspaceRoot}/.eslintrc.json",
         "{workspaceRoot}/.eslintignore",
-        "{workspaceRoot}/eslint.config.cjs",
+        "{workspaceRoot}/eslint.config.mjs",
       ],
     },
     "build": {