Add GRADLE_ACTIONS_CACHE_USE_VENDORED env var for test configuration

Add env var that forces the vendored caching module when set to
'true', decoupling module selection from the Develocity access key.
Set it centrally in init-integ-test so all tests use the vendored
module by default.

Add a dedicated legacy caching integration test that overrides the
env var to 'false' to verify the legacy module works correctly.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

.github/actions/init-integ-test/action.yml

@@ -19,6 +19,7 @@ runs:
       shell: bash
       run: |
         echo "ALLOWED_GRADLE_WRAPPER_CHECKSUMS=e3b0c44298fc1c149afbf4c8996fb92427ae41e4649b934ca495991b7852b855" >> "$GITHUB_ENV"
+        echo "GRADLE_ACTIONS_CACHE_USE_VENDORED=true" >> "$GITHUB_ENV"
 
     # Downloads a 'dist' directory artifact that was uploaded in an earlier 'build-dist' step
     - name: Download dist

.github/workflows/integ-test-legacy-caching.yml

@@ -0,0 +1,66 @@
+name: Test legacy caching module
+
+on:
+  workflow_call:
+    inputs:
+      cache-key-prefix:
+        type: string
+        default: '0'
+      runner-os:
+        type: string
+        default: '["ubuntu-latest"]'
+      skip-dist:
+        type: boolean
+        default: false
+
+env:
+  SKIP_DIST: ${{ inputs.skip-dist }}
+  GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX: legacy-caching-${{ inputs.cache-key-prefix }}
+  GRADLE_ACTIONS_CACHE_USE_VENDORED: false
+
+permissions:
+  contents: read
+
+jobs:
+  legacy-caching-seed-build:
+    strategy:
+      max-parallel: 1
+      fail-fast: false
+      matrix:
+        os: ${{fromJSON(inputs.runner-os)}}
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+    - name: Initialize integ-test
+      uses: ./.github/actions/init-integ-test
+
+    - name: Setup Gradle
+      uses: ./setup-gradle
+      with:
+        cache-read-only: false # For testing, allow writing cache entries on non-default branches
+    - name: Build kotlin-dsl project
+      working-directory: .github/workflow-samples/kotlin-dsl
+      run: ./gradlew build
+
+  legacy-caching-verify-build:
+    needs: legacy-caching-seed-build
+    strategy:
+      max-parallel: 1
+      fail-fast: false
+      matrix:
+        os: ${{fromJSON(inputs.runner-os)}}
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@de0fac2e4500dabe0009e67214ff5f5447ce83dd # v6.0.2
+    - name: Initialize integ-test
+      uses: ./.github/actions/init-integ-test
+
+    - name: Setup Gradle
+      uses: ./setup-gradle
+      with:
+        cache-read-only: true
+    - name: Build kotlin-dsl project
+      working-directory: .github/workflow-samples/kotlin-dsl
+      run: ./gradlew build --offline

.github/workflows/suite-integ-test-caching.yml

@@ -45,3 +45,8 @@ jobs:
     uses: ./.github/workflows/integ-test-restore-java-toolchain.yml
     with:
       skip-dist: ${{ inputs.skip-dist }}
+
+  legacy-caching:
+    uses: ./.github/workflows/integ-test-legacy-caching.yml
+    with:
+      skip-dist: ${{ inputs.skip-dist }}

sources/src/cache-service-loader.ts

@@ -59,7 +59,7 @@ export async function getCacheService(cacheConfig: CacheConfig): Promise<CacheSe
         return new NoOpCacheService()
     }
 
-    if (cacheConfig.isCacheLicenseAccepted()) {
+    if (useVendoredCacheModule() || cacheConfig.isCacheLicenseAccepted()) {
         const vendoredService = await loadVendoredCacheService()
         return new LoggingCacheService(vendoredService, VENDORED_CACHE_LOG_MESSAGE, VENDORED_CACHE_REPORT_NOTICE)
     }
@@ -68,6 +68,10 @@ export async function getCacheService(cacheConfig: CacheConfig): Promise<CacheSe
     return new LoggingCacheService(legacyService, LEGACY_CACHE_LOG_MESSAGE, LEGACY_CACHE_REPORT_NOTICE)
 }
 
+function useVendoredCacheModule(): boolean {
+    return process.env['GRADLE_ACTIONS_CACHE_USE_VENDORED'] === 'true'
+}
+
 export async function loadVendoredCacheService(): Promise<CacheService> {
     const vendoredLibraryPath = findLibraryPath('sources/vendor/gradle-actions-caching/index.js')
     const moduleUrl = pathToFileURL(vendoredLibraryPath).href