telemetry: collect feature usage for linting during build

Currently, we have telemetry to measure how ESLint is invoked,
but we do not have telemetry that tells us how many users have
disabled ESLint during build.

This commit adds a new feature, `build lint` to track this metric.

packages/next/build/index.ts

@@ -243,7 +243,8 @@ export default async function build(
 
     const ignoreESLint = Boolean(config.eslint.ignoreDuringBuilds)
     const eslintCacheDir = path.join(cacheDir, 'eslint/')
-    if (!ignoreESLint && runLint) {
+    const shouldLint = !ignoreESLint && runLint
+    if (shouldLint) {
       await nextBuildSpan
         .traceChild('verify-and-lint')
         .traceAsyncFn(async () => {
@@ -257,6 +258,14 @@ export default async function build(
           )
         })
     }
+    const buildLintEvent: EventBuildFeatureUsage = {
+      featureName: 'build lint',
+      invocationCount: shouldLint ? 1 : 0,
+    }
+    telemetry.record({
+      eventName: EVENT_BUILD_FEATURE_USAGE,
+      payload: buildLintEvent,
+    })
 
     const buildSpinner = createSpinner({
       prefixText: `${Log.prefixes.info} Creating an optimized production build`,

packages/next/telemetry/events/build.ts

@@ -134,6 +134,7 @@ export type EventBuildFeatureUsage = {
     | 'optimizeFonts'
     | 'swcLoader'
     | 'swcMinify'
+    | 'build lint'
   invocationCount: number
 }
 export function eventBuildFeatureUsage(

test/integration/telemetry/test/index.test.js

@@ -541,6 +541,46 @@ describe('Telemetry CLI', () => {
     expect(event1).toMatch(/"nextEslintPluginVersion": ".*?\..*?\..*?"/)
     expect(event1).toMatch(/"nextEslintPluginErrorsCount": \d{1,}/)
     expect(event1).toMatch(/"nextEslintPluginWarningsCount": \d{1,}/)
+
+    const event2 = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/
+      .exec(stderr)
+      .pop()
+    expect(event2).toContain(`"featureName": "build lint"`)
+    expect(event2).toContain(`"invocationCount": 1`)
+  })
+
+  it(`emits telemetry for lint during build when '--no-lint' is specified`, async () => {
+    const { stderr } = await nextBuild(appDir, ['--no-lint'], {
+      stderr: true,
+      env: { NEXT_TELEMETRY_DEBUG: 1 },
+    })
+
+    const event1 = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/
+      .exec(stderr)
+      .pop()
+
+    expect(event1).toContain(`"featureName": "build lint"`)
+    expect(event1).toContain(`"invocationCount": 0`)
+  })
+
+  it(`emits telemetry for lint during build when 'ignoreDuringBuilds' is specified`, async () => {
+    const nextConfig = path.join(appDir, 'next.config.js')
+    await fs.writeFile(
+      nextConfig,
+      `module.exports = { eslint: { ignoreDuringBuilds: true } }`
+    )
+    const { stderr } = await nextBuild(appDir, [], {
+      stderr: true,
+      env: { NEXT_TELEMETRY_DEBUG: 1 },
+    })
+    await fs.remove(nextConfig)
+
+    const event1 = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/
+      .exec(stderr)
+      .pop()
+
+    expect(event1).toContain(`"featureName": "build lint"`)
+    expect(event1).toContain(`"invocationCount": 0`)
   })
 
   it('emits telemetry for `next lint`', async () => {
@@ -575,6 +615,7 @@ describe('Telemetry CLI', () => {
     })
     const regex = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/g
     regex.exec(stderr).pop() // optimizeCss
+    regex.exec(stderr).pop() // build lint
     const optimizeFonts = regex.exec(stderr).pop()
     expect(optimizeFonts).toContain(`"featureName": "optimizeFonts"`)
     expect(optimizeFonts).toContain(`"invocationCount": 1`)
@@ -612,6 +653,7 @@ describe('Telemetry CLI', () => {
     )
 
     const regex = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/g
+    regex.exec(stderr).pop() // build lint
     const optimizeCss = regex.exec(stderr).pop()
     expect(optimizeCss).toContain(`"featureName": "experimental/optimizeCss"`)
     expect(optimizeCss).toContain(`"invocationCount": 1`)