fix(nextjs): ensure eslint-config-next matches Next.js 14 and 15 versions

packages/next/src/generators/application/application.spec.ts

@@ -691,6 +691,47 @@ describe('app', () => {
         `);
       });
 
+      it('should install eslint-config-next@15 when generating a new Next.js application in an empty Nx workspace', async () => {
+        const name = uniq();
+        await applicationGenerator(tree, {
+          directory: name,
+          style: 'css',
+        });
+
+        const packageJson = readJson(tree, '/package.json');
+        expect(packageJson).toMatchObject({
+          devDependencies: {
+            'eslint-config-next': '~15.1.4',
+          },
+        });
+      });
+
+      it('should install eslint-config-next@14 when an existing Next.js 14 project is detected', async () => {
+        tree.write(
+          '/package.json',
+          JSON.stringify({
+            name: '@proj/source',
+            dependencies: {
+              next: '~14.2.16',
+            },
+            devDependencies: {},
+          })
+        );
+
+        const name = uniq();
+        await applicationGenerator(tree, {
+          directory: name,
+          style: 'css',
+        });
+
+        const packageJson = readJson(tree, '/package.json');
+        expect(packageJson).toMatchObject({
+          devDependencies: {
+            'eslint-config-next': '~14.2.16',
+          },
+        });
+      });
+
       it('should add .eslintrc.json and dependencies', async () => {
         await applicationGenerator(tree, {
           directory: 'myapp',

packages/next/src/generators/application/lib/add-linting.ts

@@ -15,7 +15,7 @@ import {
   isEslintConfigSupported,
   updateOverrideInLintConfig,
 } from '@nx/eslint/src/generators/utils/eslint-file';
-import { eslintConfigNextVersion } from '../../../utils/versions';
+import { getEslintConfigNextDependenciesVersionsToInstall } from '../../../utils/version-utils';
 import { useFlatConfig } from '@nx/eslint/src/utils/flat-config';
 
 export async function addLinting(
@@ -95,10 +95,13 @@ export async function addLinting(
   }
 
   if (!options.skipPackageJson) {
+    const eslintConfigNextVersions =
+      await getEslintConfigNextDependenciesVersionsToInstall(host);
+
     tasks.push(
       addDependenciesToPackageJson(host, extraEslintDependencies.dependencies, {
         ...extraEslintDependencies.devDependencies,
-        'eslint-config-next': eslintConfigNextVersion,
+        'eslint-config-next': eslintConfigNextVersions.eslintConfigNextVersion,
       })
     );
   }

packages/next/src/utils/version-utils.ts

@@ -1,11 +1,20 @@
 import { type Tree, readJson, createProjectGraphAsync } from '@nx/devkit';
 import { clean, coerce, major } from 'semver';
-import { nextVersion, next14Version } from './versions';
+import {
+  nextVersion,
+  next14Version,
+  eslintConfigNext14Version,
+  eslintConfigNextVersion,
+} from './versions';
 
 type NextDependenciesVersions = {
   next: string;
 };
 
+type EslintConfigNextVersions = {
+  eslintConfigNextVersion: string;
+};
+
 export async function getNextDependenciesVersionsToInstall(
   tree: Tree,
   isReact18 = false
@@ -21,6 +30,20 @@ export async function getNextDependenciesVersionsToInstall(
   }
 }
 
+export async function getEslintConfigNextDependenciesVersionsToInstall(
+  tree: Tree
+): Promise<EslintConfigNextVersions> {
+  if (await isNext14(tree)) {
+    return {
+      eslintConfigNextVersion: eslintConfigNext14Version,
+    };
+  } else {
+    return {
+      eslintConfigNextVersion: eslintConfigNextVersion,
+    };
+  }
+}
+
 export async function isNext14(tree: Tree) {
   let installedNextVersion = await getInstalledNextVersionFromGraph();
   if (!installedNextVersion) {

packages/next/src/utils/versions.ts

@@ -2,7 +2,8 @@ export const nxVersion = require('../../package.json').version;
 
 export const nextVersion = '~15.1.4';
 export const next14Version = '~14.2.16';
-export const eslintConfigNextVersion = '14.2.16';
+export const eslintConfigNextVersion = '~15.1.4';
+export const eslintConfigNext14Version = '~14.2.16';
 export const sassVersion = '1.62.1';
 export const lessLoader = '11.1.0';
 export const emotionServerVersion = '11.11.0';