Add experimental support for cache-cleanup

- Includes basic implementation as `CacheCleaner`
- Integration test that checks unused files are removed:
  - Downloaded dependencies
  - Local build cache entries
  - Wrapper distributions

src/cache-cleaner.ts

@@ -0,0 +1,52 @@
+import * as exec from '@actions/exec'
+import fs from 'fs'
+import path from 'path'
+
+export class CacheCleaner {
+    private readonly gradleUserHome: string
+    private readonly tmpDir: string
+
+    constructor(gradleUserHome: string, tmpDir: string) {
+        this.gradleUserHome = gradleUserHome
+        this.tmpDir = tmpDir
+    }
+
+    async prepare(): Promise<void> {
+        fs.rmSync(path.resolve(this.gradleUserHome, 'caches/journal-1'), {recursive: true, force: true})
+        fs.mkdirSync(path.resolve(this.gradleUserHome, 'caches/journal-1'), {recursive: true})
+        fs.writeFileSync(
+            path.resolve(this.gradleUserHome, 'caches/journal-1/file-access.properties'),
+            'inceptionTimestamp=0'
+        )
+        await this.ageAllFiles()
+        await this.touchAllFiles('gc.properties')
+    }
+
+    async forceCleanup(): Promise<void> {
+        await this.ageAllFiles('gc.properties')
+
+        const cleanupProjectDir = path.resolve(this.tmpDir, 'dummy-cleanup-project')
+        fs.mkdirSync(cleanupProjectDir, {recursive: true})
+        fs.writeFileSync(
+            path.resolve(cleanupProjectDir, 'settings.gradle'),
+            'rootProject.name = "dummy-cleanup-project"'
+        )
+        fs.writeFileSync(path.resolve(cleanupProjectDir, 'build.gradle'), 'task("noop") {}')
+
+        await exec.exec(`gradle -g ${this.gradleUserHome} --no-daemon --build-cache --no-scan --quiet noop`, [], {
+            cwd: cleanupProjectDir
+        })
+    }
+
+    private async ageAllFiles(fileName = '*'): Promise<void> {
+        await exec.exec(
+            'find',
+            [this.gradleUserHome, '-name', fileName, '-exec', 'touch', '-m', '-d', '1970-01-01', '{}', '+'],
+            {}
+        )
+    }
+
+    private async touchAllFiles(fileName = '*'): Promise<void> {
+        await exec.exec('find', [this.gradleUserHome, '-name', fileName, '-exec', 'touch', '-m', '{}', '+'], {})
+    }
+}

src/cache-utils.ts

@@ -16,6 +16,7 @@ const CACHE_DISABLED_PARAMETER = 'cache-disabled'
 const CACHE_READONLY_PARAMETER = 'cache-read-only'
 const CACHE_WRITEONLY_PARAMETER = 'cache-write-only'
 const STRICT_CACHE_MATCH_PARAMETER = 'gradle-home-cache-strict-match'
+const CACHE_CLEANUP_ENABLED_PARAMETER = 'gradle-home-cache-cleanup'
 const CACHE_DEBUG_VAR = 'GRADLE_BUILD_ACTION_CACHE_DEBUG_ENABLED'
 
 const CACHE_KEY_PREFIX_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX'
@@ -46,6 +47,10 @@ export function isCacheDebuggingEnabled(): boolean {
     return process.env[CACHE_DEBUG_VAR] ? true : false
 }
 
+export function isCacheCleanupEnabled(): boolean {
+    return core.getBooleanInput(CACHE_CLEANUP_ENABLED_PARAMETER)
+}
+
 /**
  * Represents a key used to restore a cache entry.
  * The Github Actions cache will first try for an exact match on the key.

src/caches.ts

@@ -1,8 +1,9 @@
 import * as core from '@actions/core'
-import {isCacheDisabled, isCacheReadOnly, isCacheWriteOnly} from './cache-utils'
+import {isCacheCleanupEnabled, isCacheDisabled, isCacheReadOnly, isCacheWriteOnly} from './cache-utils'
 import {CacheListener} from './cache-reporting'
 import {DaemonController} from './daemon-controller'
 import {GradleStateCache} from './cache-base'
+import {CacheCleaner} from './cache-cleaner'
 
 const CACHE_RESTORED_VAR = 'GRADLE_BUILD_ACTION_CACHE_RESTORED'
 
@@ -44,6 +45,10 @@ export async function restore(gradleUserHome: string, cacheListener: CacheListen
     await core.group('Restore Gradle state from cache', async () => {
         await gradleStateCache.restore(cacheListener)
     })
+
+    if (isCacheCleanupEnabled() && !isCacheReadOnly()) {
+        new CacheCleaner(gradleUserHome, process.env['RUNNER_TEMP']!).prepare()
+    }
 }
 
 export async function save(
@@ -69,6 +74,10 @@ export async function save(
 
     await daemonController.stopAllDaemons()
 
+    if (isCacheCleanupEnabled()) {
+        new CacheCleaner(gradleUserHome, process.env['RUNNER_TEMP']!).forceCleanup()
+    }
+
     await core.group('Caching Gradle state', async () => {
         return new GradleStateCache(gradleUserHome).save(cacheListener)
     })