Automatic caching of dependencies

in a best effort manner by default
allowing to specify files to hash for computing the cache key

src/cache-dependencies.ts

@@ -0,0 +1,72 @@
+import * as path from 'path'
+import * as fs from 'fs'
+import * as os from 'os'
+
+import * as core from '@actions/core'
+import * as cache from '@actions/cache'
+
+import * as github from './github-utils'
+import * as crypto from './crypto-utils'
+
+const DEPENDENCIES_CACHE_PATH = 'DEPENDENCIES_CACHE_PATH'
+const DEPENDENCIES_CACHE_KEY = 'DEPENDENCIES_CACHE_KEY'
+const DEPENDENCIES_CACHE_RESULT = 'DEPENDENCIES_CACHE_RESULT'
+
+export async function restoreCachedDependencies(
+    rootDir: string
+): Promise<void> {
+    const cachePath = path.resolve(os.homedir(), '.gradle/caches/modules-2')
+    core.saveState(DEPENDENCIES_CACHE_PATH, cachePath)
+
+    const inputCacheKeyGlobs = github.inputArrayOrNull('dependencies-cache-key')
+    const cacheKeyGlobs = inputCacheKeyGlobs
+        ? inputCacheKeyGlobs
+        : [
+              '**/*.gradle',
+              '**/*.gradle.kts',
+              '**/gradle.properties',
+              'gradle/**'
+          ]
+
+    const hash = await crypto.hashFiles(rootDir, cacheKeyGlobs)
+    const cacheKeyPrefix = 'dependencies-'
+    const cacheKey = `${cacheKeyPrefix}${hash}`
+    core.saveState(DEPENDENCIES_CACHE_KEY, cacheKey)
+
+    const cacheResult = await cache.restoreCache([cachePath], cacheKey, [
+        cacheKeyPrefix
+    ])
+    core.saveState(DEPENDENCIES_CACHE_RESULT, cacheResult)
+}
+
+export async function cacheDependencies(): Promise<void> {
+    const cachePath = core.getState(DEPENDENCIES_CACHE_PATH)
+    const cacheKey = core.getState(DEPENDENCIES_CACHE_KEY)
+    const cacheResult = core.getState(DEPENDENCIES_CACHE_RESULT)
+
+    if (!cachePath || !fs.existsSync(cachePath)) {
+        core.debug('No dependencies to cache.')
+        return
+    }
+
+    if (cacheResult && cacheKey === cacheResult) {
+        core.info(
+            `Dependencies cache hit occurred on the cache key ${cacheKey}, not saving cache.`
+        )
+        return
+    }
+
+    try {
+        await cache.saveCache([cachePath], cacheKey)
+    } catch (error) {
+        if (error.name === cache.ValidationError.name) {
+            throw error
+        } else if (error.name === cache.ReserveCacheError.name) {
+            core.info(error.message)
+        } else {
+            core.info(`[warning] ${error.message}`)
+        }
+    }
+
+    return
+}