Remove automatic linting from build

docs/01-app/01-getting-started/01-installation.mdx

@@ -344,7 +344,7 @@ npx @next/codemod@canary next-lint-to-eslint-cli .
 
 If you use ESLint, create an explicit config (recommended `eslint.config.mjs`). ESLint supports both [the legacy `.eslintrc.*` and the newer `eslint.config.mjs` formats](https://eslint.org/docs/latest/use/configure/configuration-files#configuring-eslint). See the [ESLint API reference](/docs/app/api-reference/config/eslint#with-core-web-vitals) for a recommended setup.
 
-> **Good to know**: If an ESLint config is present, `next build` will still run linting in Next.js 15, but this automatic build-time linting will be removed in Next.js 16. Control when linting runs by invoking your linter via npm scripts.
+> **Good to know**: Prior to Next.js 16, `next build` ran linting automatically. Now, this automatic build-time linting has been removed. Control when linting runs by invoking your linter via npm scripts.
 
 See the [ESLint Plugin](/docs/app/api-reference/config/next-config-js/eslint) page for more information.
 

packages/next/src/build/index.ts

@@ -901,7 +901,6 @@ export default async function build(
   reactProductionProfiling = false,
   debugOutput = false,
   debugPrerender = false,
-  runLint = true,
   noMangling = false,
   appDirOnly = false,
   isTurbopack = false,
@@ -1084,16 +1083,10 @@ export default async function build(
         experimentalFeatures,
       })
 
-      const ignoreESLint = Boolean(config.eslint.ignoreDuringBuilds)
-      const shouldLint = !ignoreESLint && runLint
-
       const typeCheckingOptions: Parameters<typeof startTypeChecking>[0] = {
         dir,
         appDir,
         pagesDir,
-        runLint,
-        shouldLint,
-        ignoreESLint,
         telemetry,
         nextBuildSpan,
         config,
@@ -1132,15 +1125,6 @@ export default async function build(
         process.exit(1)
       }
 
-      const buildLintEvent: EventBuildFeatureUsage = {
-        featureName: 'build-lint',
-        invocationCount: shouldLint ? 1 : 0,
-      }
-      telemetry.record({
-        eventName: EVENT_BUILD_FEATURE_USAGE,
-        payload: buildLintEvent,
-      })
-
       const validFileMatcher = createValidFileMatcher(
         config.pageExtensions,
         appDir

packages/next/src/build/type-check.ts

@@ -2,10 +2,8 @@ import type { NextConfigComplete } from '../server/config-shared'
 import type { Telemetry } from '../telemetry/storage'
 import type { Span } from '../trace'
 
-import path from 'path'
 import * as Log from './output/log'
 import { Worker } from '../lib/worker'
-import { verifyAndLint } from '../lib/verifyAndLint'
 import createSpinner from './spinner'
 import { eventTypeCheckCompleted } from '../telemetry/events'
 import isError from '../lib/is-error'
@@ -71,57 +69,36 @@ export async function startTypeChecking({
   cacheDir,
   config,
   dir,
-  ignoreESLint,
   nextBuildSpan,
   pagesDir,
-  runLint,
-  shouldLint,
   telemetry,
   appDir,
 }: {
   cacheDir: string
   config: NextConfigComplete
   dir: string
-  ignoreESLint: boolean
   nextBuildSpan: Span
   pagesDir?: string
-  runLint: boolean
-  shouldLint: boolean
   telemetry: Telemetry
   appDir?: string
 }) {
   const ignoreTypeScriptErrors = Boolean(config.typescript.ignoreBuildErrors)
 
-  const eslintCacheDir = path.join(cacheDir, 'eslint/')
-
   if (ignoreTypeScriptErrors) {
     Log.info('Skipping validation of types')
   }
-  if (runLint && ignoreESLint) {
-    // only print log when build require lint while ignoreESLint is enabled
-    Log.info('Skipping linting')
-  }
 
-  let typeCheckingAndLintingSpinnerPrefixText: string | undefined
-  let typeCheckingAndLintingSpinner:
-    | ReturnType<typeof createSpinner>
-    | undefined
+  let typeCheckingSpinnerPrefixText: string | undefined
+  let typeCheckingSpinner: ReturnType<typeof createSpinner> | undefined
 
-  if (!ignoreTypeScriptErrors && shouldLint) {
-    typeCheckingAndLintingSpinnerPrefixText =
-      'Linting and checking validity of types'
-  } else if (!ignoreTypeScriptErrors) {
-    typeCheckingAndLintingSpinnerPrefixText = 'Checking validity of types'
-  } else if (shouldLint) {
-    typeCheckingAndLintingSpinnerPrefixText = 'Linting'
+  if (!ignoreTypeScriptErrors) {
+    typeCheckingSpinnerPrefixText = 'Checking validity of types'
   }
 
-  // we will not create a spinner if both ignoreTypeScriptErrors and ignoreESLint are
-  // enabled, but we will still verifying project's tsconfig and dependencies.
-  if (typeCheckingAndLintingSpinnerPrefixText) {
-    typeCheckingAndLintingSpinner = createSpinner(
-      typeCheckingAndLintingSpinnerPrefixText
-    )
+  // we will not create a spinner if ignoreTypeScriptErrors is enabled,
+  // but we will still verify project's tsconfig and dependencies.
+  if (typeCheckingSpinnerPrefixText) {
+    typeCheckingSpinner = createSpinner(typeCheckingSpinnerPrefixText)
   }
 
   const typeCheckStart = process.hrtime()
@@ -145,18 +122,8 @@ export async function startTypeChecking({
           return [resolved, checkEnd] as const
         })
       ),
-      shouldLint &&
-        nextBuildSpan.traceChild('verify-and-lint').traceAsyncFn(async () => {
-          await verifyAndLint(
-            dir,
-            eslintCacheDir,
-            config.eslint?.dirs,
-            config.experimental.workerThreads,
-            telemetry
-          )
-        }),
     ])
-    typeCheckingAndLintingSpinner?.stopAndPersist()
+    typeCheckingSpinner?.stopAndPersist()
 
     if (!ignoreTypeScriptErrors && verifyResult) {
       telemetry.record(

packages/next/src/cli/next-build.ts

@@ -94,7 +94,6 @@ const nextBuild = (options: NextBuildOptions, directory?: string) => {
     profile,
     debug || Boolean(process.env.NEXT_DEBUG_BUILD),
     debugPrerender,
-    lint,
     !mangling,
     experimentalAppOnly,
     isTurbopack,