ci(v2): fail CI if build takes too much time (#4516)

* remove the .cache folder so that it removes both webpack cache-loader-v4/persistent-cache-v5 + webpack terser cache

* Add GH action to track build time perf with a timeout

* Add GH action to track build time perf with a timeout

.github/workflows/v2-build-blog-only.yml

@@ -9,7 +9,7 @@ on:
       - 'packages/docusaurus/**'
 
 jobs:
-  lint:
+  build:
     timeout-minutes: 30
     runs-on: ubuntu-latest
     steps:

.github/workflows/v2-build-time-perf.yml

@@ -0,0 +1,35 @@
+name: V2 Build Time Perf
+
+on:
+  pull_request:
+    branches:
+      - master
+    paths-ignore:
+      - 'website/docs/**'
+      - 'website-1.x/**'
+      - 'packages/docusaurus-1.x/**'
+      - 'packages/docusaurus-init-1.x/**'
+
+jobs:
+  build:
+    timeout-minutes: 30
+    runs-on: ubuntu-latest
+    steps:
+      - uses: actions/checkout@v2
+      - uses: actions/setup-node@v2
+      - name: Installation
+        uses: bahmutov/npm-install@v1
+        with:
+          install-command: yarn
+
+      # Ensure build with a cold cache does not increase too much
+      - name: Build (cold cache)
+        run: yarn workspace docusaurus-2-website build
+        timeout-minutes: 10
+
+      # Ensure build with a warm cache does not increase too much
+      - name: Build (warm cache)
+        run: yarn workspace docusaurus-2-website build
+        timeout-minutes: 10
+
+    # TODO post a Github comment with build with perf warnings?

packages/docusaurus/src/commands/clear.ts

@@ -25,6 +25,6 @@ export default async function clear(siteDir: string): Promise<unknown> {
   return Promise.all([
     removePath(path.join(siteDir, GENERATED_FILES_DIR_NAME)),
     removePath(path.join(siteDir, DEFAULT_BUILD_DIR_NAME)),
-    removePath(path.join(siteDir, 'node_modules/.cache/cache-loader')),
+    removePath(path.join(siteDir, 'node_modules', '.cache')),
   ]);
 }