Tests: Share built JavaScript assets across PHP workflows (#60428)

Share the npm run build result across PHP unit test workflows.

The PHP unit tests are one of the slowest parts of the unit tests and are run 19 times for every workflow run. The longest step in the runs is building the same JavaScript assets. By building once and reusing these assets we can save a significant amount of time. Around 1 hour of total CI runner time is saved for every run of the unit-test workflow.

Co-authored-by: sirreal <[email protected]>
Co-authored-by: desrosj <[email protected]>

.github/workflows/unit-test.yml

@@ -80,9 +80,29 @@ jobs:
                   echo "previous-wordpress-version=${PREVIOUS_WP_VERSION}" >> $GITHUB_OUTPUT
                   rm versions.json
 
+    build-assets:
+        name: Build JavaScript assets for PHP unit tests
+        runs-on: ubuntu-latest
+        steps:
+            - uses: actions/checkout@9bb56186c3b09b4f86b1c65136769dd318469633 # v4.1.2
+              with:
+                  show-progress: ${{ runner.debug == '1' && 'true' || 'false' }}
+
+            - name: Setup Node.js and install dependencies
+              uses: ./.github/setup-node
+
+            - name: Run build scripts
+              run: npm run build
+
+            - name: Upload built JavaScript assets
+              uses: actions/upload-artifact@5d5d22a31266ced268874388b861e4b58bb5c2f3 # v4.3.1
+              with:
+                  name: build-assets
+                  path: ./build/
+
     test-php:
         name: PHP ${{ matrix.php }}${{ matrix.multisite && ' multisite' || '' }}${{ matrix.wordpress != '' && format( ' (WP {0}) ', matrix.wordpress ) || '' }} on ubuntu-latest
-        needs: compute-previous-wordpress-version
+        needs: [compute-previous-wordpress-version, build-assets]
         runs-on: ubuntu-latest
         timeout-minutes: 20
         if: ${{ github.repository == 'WordPress/gutenberg' || github.event_name == 'pull_request' }}
@@ -152,8 +172,11 @@ jobs:
               with:
                   custom-cache-suffix: $(/bin/date -u --date='last Mon' "+%F")
 
-            - name: Npm build
-              run: npm run build
+            - name: Download built JavaScript assets
+              uses: actions/download-artifact@c850b930e6ba138125429b7e5c93fc707a7f8427 # v4.1.4
+              with:
+                  name: build-assets
+                  path: ./build
 
             - name: Docker debug information
               run: |
@@ -165,7 +188,6 @@ jobs:
                   node --version
                   curl --version
                   git --version
-                  svn --version
                   locale -a
 
             - name: Start Docker environment