Allow cache to overwrite existing Gradle User Home

Fixes #480

.github/workflows/integ-test-restore-gradle-home.yml

@@ -99,3 +99,40 @@ jobs:
       working-directory: .github/workflow-samples/groovy-dsl
       run: ./gradlew test
 
+  # Test that a pre-existing gradle-user-home can be overwritten by the restored cache
+  pre-existing-gradle-home:
+    needs: seed-build
+    strategy:
+      matrix:
+        os: ${{fromJSON(inputs.runner-os)}}
+    runs-on: ${{ matrix.os }}
+    steps:
+    - name: Checkout sources
+      uses: actions/checkout@v3
+    - name: Download distribution if required
+      uses: ./.github/actions/download-dist
+    - name: Pre-create Gradle User Home
+      shell: bash
+      run: |
+        mkdir -p ~/.gradle/caches
+        touch ~/.gradle/gradle.properties
+        touch ~/.gradle/caches/dummy.txt
+    - name: Setup Gradle
+      uses: ./
+      with:
+        cache-read-only: true
+        cache-overwrite-existing: true
+    - name: Check that pre-existing content still exists
+      shell: bash
+      run: |
+        if [ ! -e ~/.gradle/caches/dummy.txt ]; then
+          echo "::error ::Should find dummy.txt after cache restore"
+          exit 1
+        fi
+        if [ ! -e ~/.gradle/gradle.properties ]; then
+          echo "::error ::Should find gradle.properties after cache restore"
+          exit 1
+        fi
+    - name: Execute Gradle build with --offline
+      working-directory: .github/workflow-samples/groovy-dsl
+      run: ./gradlew test --offline

action.yml

@@ -35,6 +35,11 @@ inputs:
     required: false
     default: false
 
+  cache-overwrite-existing:
+    description: When 'true', a pre-existing Gradle User Home will not prevent the cache from being restored.
+    required: false
+    default: false
+
   gradle-home-cache-includes:
     description: Paths within Gradle User Home to cache.
     required: false

src/cache-utils.ts

@@ -37,6 +37,10 @@ export function isCacheWriteOnly(): boolean {
     return params.isCacheWriteOnly()
 }
 
+export function isCacheOverwriteExisting(): boolean {
+    return params.isCacheOverwriteExisting()
+}
+
 export function isCacheDebuggingEnabled(): boolean {
     return params.isCacheDebuggingEnabled()
 }

src/caches.ts

@@ -1,5 +1,11 @@
 import * as core from '@actions/core'
-import {isCacheCleanupEnabled, isCacheDisabled, isCacheReadOnly, isCacheWriteOnly} from './cache-utils'
+import {
+    isCacheCleanupEnabled,
+    isCacheDisabled,
+    isCacheReadOnly,
+    isCacheWriteOnly,
+    isCacheOverwriteExisting
+} from './cache-utils'
 import {CacheListener} from './cache-reporting'
 import {DaemonController} from './daemon-controller'
 import {GradleStateCache} from './cache-base'
@@ -26,12 +32,15 @@ export async function restore(gradleUserHome: string, cacheListener: CacheListen
     }
 
     if (gradleStateCache.cacheOutputExists()) {
-        core.info('Gradle User Home already exists: will not restore from cache.')
-        // Initialize pre-existing Gradle User Home.
-        gradleStateCache.init()
-        cacheListener.cacheDisabled = true
-        cacheListener.cacheDisabledReason = 'disabled due to pre-existing Gradle User Home'
-        return
+        if (!isCacheOverwriteExisting()) {
+            core.info('Gradle User Home already exists: will not restore from cache.')
+            // Initialize pre-existing Gradle User Home.
+            gradleStateCache.init()
+            cacheListener.cacheDisabled = true
+            cacheListener.cacheDisabledReason = 'disabled due to pre-existing Gradle User Home'
+            return
+        }
+        core.info('Gradle User Home already exists: will overwrite with cached contents.')
     }
 
     gradleStateCache.init()

src/input-params.ts

@@ -13,6 +13,10 @@ export function isCacheWriteOnly(): boolean {
     return getBooleanInput('cache-write-only')
 }
 
+export function isCacheOverwriteExisting(): boolean {
+    return getBooleanInput('cache-overwrite-existing')
+}
+
 export function isCacheStrictMatch(): boolean {
     return getBooleanInput('gradle-home-cache-strict-match')
 }