[ESLint] Adds --max-warnings flag to next lint (#26697)

Adds `--max-warnings` flag to `next lint` to enable setting of a maximum warning threshold.

Fixes #26671

Author: housseindjirdeh

packages/next/cli/next-lint.ts

@@ -55,6 +55,7 @@ const nextLint: cliCommand = (argv) => {
     '--ignore-path': String,
     '--no-ignore': Boolean,
     '--quiet': Boolean,
+    '--max-warnings': Number,
     '--no-inline-config': Boolean,
     '--report-unused-disable-directives': String,
     '--cache': Boolean,
@@ -108,6 +109,7 @@ const nextLint: cliCommand = (argv) => {
 
         Handling warnings:
           --quiet                        Report errors only - default: false
+          --max-warnings Int             Number of warnings to trigger nonzero exit code - default: -1
 
         Inline configuration comments:
           --no-inline-config             Prevent comments from changing config or rules
@@ -143,8 +145,16 @@ const nextLint: cliCommand = (argv) => {
   )
 
   const reportErrorsOnly = Boolean(args['--quiet'])
-
-  runLintCheck(baseDir, lintDirs, false, eslintOptions(args), reportErrorsOnly)
+  const maxWarnings = args['--max-warnings'] ?? -1
+
+  runLintCheck(
+    baseDir,
+    lintDirs,
+    false,
+    eslintOptions(args),
+    reportErrorsOnly,
+    maxWarnings
+  )
     .then(async (lintResults) => {
       const lintOutput =
         typeof lintResults === 'string' ? lintResults : lintResults?.output

packages/next/lib/eslint/runLintCheck.ts

@@ -6,7 +6,7 @@ import findUp from 'next/dist/compiled/find-up'
 import semver from 'next/dist/compiled/semver'
 import * as CommentJson from 'next/dist/compiled/comment-json'
 
-import { formatResults } from './customFormatter'
+import { LintResult, formatResults } from './customFormatter'
 import { writeDefaultConfig } from './writeDefaultConfig'
 import { existsSync, findPagesDir } from '../find-pages-dir'
 import {
@@ -29,7 +29,8 @@ async function lint(
   eslintrcFile: string | null,
   pkgJsonPath: string | null,
   eslintOptions: any = null,
-  reportErrorsOnly: boolean = false
+  reportErrorsOnly: boolean = false,
+  maxWarnings: number = -1
 ): Promise<
   | string
   | null
@@ -116,10 +117,16 @@ async function lint(
 
   const formattedResult = formatResults(baseDir, results)
   const lintEnd = process.hrtime(lintStart)
+  const totalWarnings = results.reduce(
+    (sum: number, file: LintResult) => sum + file.warningCount,
+    0
+  )
 
   return {
     output: formattedResult.output,
-    isError: ESLint.getErrorResults(results)?.length > 0,
+    isError:
+      ESLint.getErrorResults(results)?.length > 0 ||
+      (maxWarnings >= 0 && totalWarnings > maxWarnings),
     eventInfo: {
       durationInSeconds: lintEnd[0],
       eslintVersion: eslintVersion,
@@ -143,7 +150,8 @@ export async function runLintCheck(
   lintDirs: string[],
   lintDuringBuild: boolean = false,
   eslintOptions: any = null,
-  reportErrorsOnly: boolean = false
+  reportErrorsOnly: boolean = false,
+  maxWarnings: number = -1
 ): ReturnType<typeof lint> {
   try {
     // Find user's .eslintrc file
@@ -205,7 +213,8 @@ export async function runLintCheck(
       eslintrcFile,
       pkgJsonPath,
       eslintOptions,
-      reportErrorsOnly
+      reportErrorsOnly,
+      maxWarnings
     )
   } catch (err) {
     throw err

test/integration/eslint/max-warnings/.eslintrc

@@ -0,0 +1,8 @@
+{
+  "extends": "next",
+  "root": true,
+  "rules": {
+    "@next/next/no-html-link-for-pages": 0,
+    "@next/next/no-sync-scripts": 1
+  }
+}

test/integration/eslint/max-warnings/pages/about.js

@@ -0,0 +1,8 @@
+const About = () => (
+  <div>
+    <p>About</p>
+    <script src="https://example.com" />
+  </div>
+)
+
+export default About

test/integration/eslint/max-warnings/pages/index.js

@@ -0,0 +1,8 @@
+const Home = () => (
+  <div>
+    <p>Home</p>
+    <script src="https://example.com" />
+  </div>
+)
+
+export default Home

test/integration/eslint/test/index.test.js

@@ -12,6 +12,7 @@ const dirIgnoreDuringBuilds = join(__dirname, '../ignore-during-builds')
 const dirCustomDirectories = join(__dirname, '../custom-directories')
 const dirConfigInPackageJson = join(__dirname, '../config-in-package-json')
 const dirInvalidEslintVersion = join(__dirname, '../invalid-eslint-version')
+const dirMaxWarnings = join(__dirname, '../max-warnings')
 
 describe('ESLint', () => {
   describe('Next Build', () => {
@@ -188,5 +189,43 @@ describe('ESLint', () => {
         'Warning: External synchronous scripts are forbidden'
       )
     })
+
+    test('max warnings flag errors when warnings exceed threshold', async () => {
+      const { stdout, stderr } = await nextLint(
+        dirMaxWarnings,
+        ['--max-warnings', 1],
+        {
+          stdout: true,
+          stderr: true,
+        }
+      )
+
+      expect(stderr).not.toEqual('')
+      expect(stderr).toContain(
+        'Warning: External synchronous scripts are forbidden'
+      )
+      expect(stdout).not.toContain(
+        'Warning: External synchronous scripts are forbidden'
+      )
+    })
+
+    test('max warnings flag does not error when warnings do not exceed threshold', async () => {
+      const { stdout, stderr } = await nextLint(
+        dirMaxWarnings,
+        ['--max-warnings', 2],
+        {
+          stdout: true,
+          stderr: true,
+        }
+      )
+
+      expect(stderr).toEqual('')
+      expect(stderr).not.toContain(
+        'Warning: External synchronous scripts are forbidden'
+      )
+      expect(stdout).toContain(
+        'Warning: External synchronous scripts are forbidden'
+      )
+    })
   })
 })