telemetry: collect feature usage for linting during build (#32022)

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.



## Bug

- [ ] Related issues linked using `fixes #number`
- [x] Integration tests added
- [ ] Errors have helpful link attached, see `contributing.md`

## Feature

- [ ] Implements an existing feature request or RFC. Make sure the feature request has been accepted for implementation before opening a PR.
- [ ] Related issues linked using `fixes #number`
- [ ] Integration tests added
- [ ] Documentation added
- [ ] Telemetry added. In case of a feature if it's used or not.
- [ ] Errors have helpful link attached, see `contributing.md`

## Documentation / Examples

- [ ] Make sure the linting passes by running `yarn lint`

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`)