From 0ab8c7ada6eb27451f362d1519e6f6214ae83007 Mon Sep 17 00:00:00 2001
From: Maia Teegarden <dev@padmaia.rocks>
Date: Tue, 26 Oct 2021 00:37:38 -0700
Subject: [PATCH] Track usage of swc features (#30297)

Co-authored-by: Tim Neutkens <timneutkens@me.com>
---
 packages/next/build/webpack-config.ts         |  9 ++++++++-
 .../build/webpack/plugins/telemetry-plugin.ts | 20 +++++++++++++++++--
 packages/next/telemetry/events/build.ts       |  2 ++
 test/integration/telemetry/test/index.test.js |  6 ++++++
 4 files changed, 34 insertions(+), 3 deletions(-)

diff --git a/packages/next/build/webpack-config.ts b/packages/next/build/webpack-config.ts
index f2b2260889ce9..e769d254880e9 100644
--- a/packages/next/build/webpack-config.ts
+++ b/packages/next/build/webpack-config.ts
@@ -1307,7 +1307,14 @@ export default async function getBaseWebpackConfig(
             minimized: true,
           },
         }),
-      !dev && !isServer && new TelemetryPlugin(),
+      !dev &&
+        !isServer &&
+        new TelemetryPlugin(
+          new Map([
+            ['swcLoader', useSWCLoader],
+            ['swcMinify', config.swcMinify],
+          ])
+        ),
     ].filter(Boolean as any as ExcludesFalse),
   }
 
diff --git a/packages/next/build/webpack/plugins/telemetry-plugin.ts b/packages/next/build/webpack/plugins/telemetry-plugin.ts
index 7093aa91fee26..e961aacb05e6f 100644
--- a/packages/next/build/webpack/plugins/telemetry-plugin.ts
+++ b/packages/next/build/webpack/plugins/telemetry-plugin.ts
@@ -1,6 +1,11 @@
 import type { webpack5 as webpack } from 'next/dist/compiled/webpack/webpack'
 
-type Feature = 'next/image' | 'next/script' | 'next/dynamic'
+type Feature =
+  | 'next/image'
+  | 'next/script'
+  | 'next/dynamic'
+  | 'swcLoader'
+  | 'swcMinify'
 
 interface FeatureUsage {
   featureName: Feature
@@ -29,6 +34,9 @@ const FEATURE_MODULE_MAP: ReadonlyMap<Feature, string> = new Map([
   ['next/dynamic', '/next/dynamic.js'],
 ])
 
+// List of build features used in webpack configuration
+const BUILD_FEATURES: Array<Feature> = ['swcLoader', 'swcMinify']
+
 /**
  * Plugin that queries the ModuleGraph to look for modules that correspond to
  * certain features (e.g. next/image and next/script) and record how many times
@@ -37,7 +45,15 @@ const FEATURE_MODULE_MAP: ReadonlyMap<Feature, string> = new Map([
 export class TelemetryPlugin implements webpack.WebpackPluginInstance {
   private usageTracker = new Map<Feature, FeatureUsage>()
 
-  constructor() {
+  // Build feature usage is on/off and is known before the build starts
+  constructor(buildFeaturesMap: Map<Feature, boolean>) {
+    for (const featureName of BUILD_FEATURES) {
+      this.usageTracker.set(featureName, {
+        featureName,
+        invocationCount: buildFeaturesMap.get(featureName) ? 1 : 0,
+      })
+    }
+
     for (const featureName of FEATURE_MODULE_MAP.keys()) {
       this.usageTracker.set(featureName, {
         featureName,
diff --git a/packages/next/telemetry/events/build.ts b/packages/next/telemetry/events/build.ts
index db354d3979e91..f4bbd962993e2 100644
--- a/packages/next/telemetry/events/build.ts
+++ b/packages/next/telemetry/events/build.ts
@@ -128,6 +128,8 @@ export type EventBuildFeatureUsage = {
     | 'next/script'
     | 'next/dynamic'
     | 'experimental/optimizeCss'
+    | 'swcLoader'
+    | 'swcMinify'
   invocationCount: number
 }
 export function eventBuildFeatureUsage(
diff --git a/test/integration/telemetry/test/index.test.js b/test/integration/telemetry/test/index.test.js
index c0784d859e309..0a01e59be41ab 100644
--- a/test/integration/telemetry/test/index.test.js
+++ b/test/integration/telemetry/test/index.test.js
@@ -569,6 +569,12 @@ describe('Telemetry CLI', () => {
     })
     const regex = /NEXT_BUILD_FEATURE_USAGE[\s\S]+?{([\s\S]+?)}/g
     regex.exec(stderr).pop() // optimizeCss
+    const swcLoader = regex.exec(stderr).pop()
+    expect(swcLoader).toContain(`"featureName": "swcLoader"`)
+    expect(swcLoader).toContain(`"invocationCount": 1`)
+    const swcMinify = regex.exec(stderr).pop()
+    expect(swcMinify).toContain(`"featureName": "swcMinify"`)
+    expect(swcMinify).toContain(`"invocationCount": 0`)
     const image = regex.exec(stderr).pop()
     expect(image).toContain(`"featureName": "next/image"`)
     expect(image).toContain(`"invocationCount": 1`)