fix: support config defined in next.config.js

test/lib/next-modes/next-start.ts

@@ -4,7 +4,7 @@ import { NextInstance } from './base'
 import spawn from 'cross-spawn'
 import { Span } from 'next/dist/trace'
 import stripAnsi from 'strip-ansi'
-import { providesESLintConfiguration } from 'next-test-utils'
+import { shouldDisableLinting } from 'next-test-utils'
 
 export class NextStartInstance extends NextInstance {
  private _buildId: string
@@ -72,7 +72,7 @@ export class NextStartInstance extends NextInstance {
 
  // Disable linting if the directory provides an ESLint configuration. This
  // prevents the project's eslint configuration from affecting the test.
- if (!providesESLintConfiguration(this.testDir)) {
+ if (shouldDisableLinting(this.testDir)) {
  buildArgs.push('--no-lint')
  }
 

test/lib/next-test-utils.ts

@@ -18,6 +18,7 @@ import fetch from 'node-fetch'
 import qs from 'querystring'
 import treeKill from 'tree-kill'
 import { once } from 'events'
+import vm from 'vm'
 
 import server from 'next/dist/server/next'
 import _pkg from 'next/package.json'
@@ -437,32 +438,61 @@ export function launchApp(
  )
 }
 
+/**
+ * Read a JavaScript file and return the exports.
+ *
+ * @param path The path to the JavaScript file.
+ * @returns The exports of the JavaScript file.
+ */
+function readJS(path: string) {
+ const data = readFileSync(path, 'utf8')
+ const script = new vm.Script(data, { filename: path })
+ const context = { module: { exports: {} } }
+ script.runInNewContext(context)
+ return context.module.exports
+}
+
 /**
  * Check if the directory provides an ESLint configuration.
  *
  * @param dir The directory to check.
  * @returns Whether the directory provides an ESLint configuration.
  */
-export function providesESLintConfiguration(dir: string) {
- // If some of these files exist, we should not disable linting.
- if (
- ['.eslintrc.json', '.eslintrc.js', '.eslintrc'].some((file) =>
- existsSync(path.join(dir, file))
- )
- ) {
- return true
- }
+export function shouldDisableLinting(dir: string) {
+ try {
+ // If the project already has a `next.config.js` file that includes an eslint
+ // config, then don't disable linting.
+ if (
+ existsSync(path.join(dir, 'next.config.js')) &&
+ 'eslint' in readJS(path.join(dir, 'next.config.js'))
+ ) {
+ return false
+ }
+ } catch {}
 
- // If the `eslintConfig` field is present in the `package.json` file, we
- // should not disable linting.
- if (
- existsSync(path.join(dir, 'package.json')) &&
- readJson(path.join(dir, 'package.json')).eslintConfig
- ) {
- return true
- }
+ try {
+ // If some of these files exist, we should not disable linting.
+ if (
+ ['.eslintrc.json', '.eslintrc.js', '.eslintrc'].some((file) =>
+ existsSync(path.join(dir, file))
+ )
+ ) {
+ return false
+ }
+ } catch {}
 
- return false
+ try {
+ // If the `eslintConfig` field is present in the `package.json` file, we
+ // should not disable linting.
+ if (
+ existsSync(path.join(dir, 'package.json')) &&
+ readJson(path.join(dir, 'package.json')).eslintConfig
+ ) {
+ return false
+ }
+ } catch {}
+
+ return true
 }
 
 export function nextBuild(
@@ -472,7 +502,7 @@ export function nextBuild(
 ) {
  // Disable linting if the directory provides an ESLint configuration. This
  // prevents the project's eslint configuration from affecting the test.
- if (!providesESLintConfiguration(dir)) args.push('--no-lint')
+ if (shouldDisableLinting(dir)) args.push('--no-lint')
 
  return runNextCommand(['build', dir, ...args], opts)
 }