Moved cache-related code into subpackage

sources/src/caching/cache-key.ts

@@ -0,0 +1,97 @@
+import * as github from '@actions/github'
+
+import {CacheConfig, getJobMatrix} from '../input-params'
+import {hashStrings} from './cache-utils'
+
+const CACHE_PROTOCOL_VERSION = 'v9-'
+
+const CACHE_KEY_PREFIX_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX'
+const CACHE_KEY_OS_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_ENVIRONMENT'
+const CACHE_KEY_JOB_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_JOB'
+const CACHE_KEY_JOB_INSTANCE_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_JOB_INSTANCE'
+const CACHE_KEY_JOB_EXECUTION_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_JOB_EXECUTION'
+
+/**
+ * Represents a key used to restore a cache entry.
+ * The Github Actions cache will first try for an exact match on the key.
+ * If that fails, it will try for a prefix match on any of the restoreKeys.
+ */
+export class CacheKey {
+    key: string
+    restoreKeys: string[]
+
+    constructor(key: string, restoreKeys: string[]) {
+        this.key = key
+        this.restoreKeys = restoreKeys
+    }
+}
+
+/**
+ * Generates a cache key specific to the current job execution.
+ * The key is constructed from the following inputs (with some user overrides):
+ * - The cache protocol version
+ * - The name of the cache
+ * - The runner operating system
+ * - The name of the workflow and Job being executed
+ * - The matrix values for the Job being executed (job context)
+ * - The SHA of the commit being executed
+ *
+ * Caches are restored by trying to match the these key prefixes in order:
+ * - The full key with SHA
+ * - A previous key for this Job + matrix
+ * - Any previous key for this Job (any matrix)
+ * - Any previous key for this cache on the current OS
+ */
+export function generateCacheKey(cacheName: string, config: CacheConfig): CacheKey {
+    const cacheKeyBase = `${getCacheKeyPrefix()}${CACHE_PROTOCOL_VERSION}${cacheName}`
+
+    // At the most general level, share caches for all executions on the same OS
+    const cacheKeyForEnvironment = `${cacheKeyBase}|${getCacheKeyEnvironment()}`
+
+    // Then prefer caches that run job with the same ID
+    const cacheKeyForJob = `${cacheKeyForEnvironment}|${getCacheKeyJob()}`
+
+    // Prefer (even more) jobs that run this job in the same workflow with the same context (matrix)
+    const cacheKeyForJobContext = `${cacheKeyForJob}[${getCacheKeyJobInstance()}]`
+
+    // Exact match on Git SHA
+    const cacheKey = `${cacheKeyForJobContext}-${getCacheKeyJobExecution()}`
+
+    if (config.isCacheStrictMatch()) {
+        return new CacheKey(cacheKey, [cacheKeyForJobContext])
+    }
+
+    return new CacheKey(cacheKey, [cacheKeyForJobContext, cacheKeyForJob, cacheKeyForEnvironment])
+}
+
+export function getCacheKeyPrefix(): string {
+    // Prefix can be used to force change all cache keys (defaults to cache protocol version)
+    return process.env[CACHE_KEY_PREFIX_VAR] || ''
+}
+
+function getCacheKeyEnvironment(): string {
+    const runnerOs = process.env['RUNNER_OS'] || ''
+    return process.env[CACHE_KEY_OS_VAR] || runnerOs
+}
+
+function getCacheKeyJob(): string {
+    return process.env[CACHE_KEY_JOB_VAR] || github.context.job
+}
+
+function getCacheKeyJobInstance(): string {
+    const override = process.env[CACHE_KEY_JOB_INSTANCE_VAR]
+    if (override) {
+        return override
+    }
+
+    // By default, we hash the workflow name and the full `matrix` data for the run, to uniquely identify this job invocation
+    // The only way we can obtain the `matrix` data is via the `workflow-job-context` parameter in action.yml.
+    const workflowName = github.context.workflow
+    const workflowJobContext = getJobMatrix()
+    return hashStrings([workflowName, workflowJobContext])
+}
+
+function getCacheKeyJobExecution(): string {
+    // Used to associate a cache key with a particular execution (default is bound to the git commit sha)
+    return process.env[CACHE_KEY_JOB_EXECUTION_VAR] || github.context.sha
+}