Allow override of sections of cache key

These internal env vars are designed primarily for testing,
but may also prove useful for folks to experiment with more optimal
caching setups.

src/cache-base.ts

@@ -1,83 +1,17 @@
 import * as core from '@actions/core'
 import * as exec from '@actions/exec'
-import * as github from '@actions/github'
 import path from 'path'
 import fs from 'fs'
 import {CacheListener} from './cache-reporting'
-import {
-    getCacheKeyPrefix,
-    determineJobContext,
-    saveCache,
-    restoreCache,
-    cacheDebug,
-    isCacheDebuggingEnabled,
-    tryDelete
-} from './cache-utils'
+import {saveCache, restoreCache, cacheDebug, isCacheDebuggingEnabled, tryDelete, generateCacheKey} from './cache-utils'
 import {ConfigurationCacheEntryExtractor, GradleHomeEntryExtractor} from './cache-extract-entries'
 
-const CACHE_PROTOCOL_VERSION = 'v6-'
 const RESTORED_CACHE_KEY_KEY = 'restored-cache-key'
 
 export const META_FILE_DIR = '.gradle-build-action'
 export const PROJECT_ROOTS_FILE = 'project-roots.txt'
 const INCLUDE_PATHS_PARAMETER = 'gradle-home-cache-includes'
 const EXCLUDE_PATHS_PARAMETER = 'gradle-home-cache-excludes'
-const STRICT_CACHE_MATCH_PARAMETER = 'gradle-home-cache-strict-match'
-
-/**
- * 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.
- */
-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:
- * - A user-defined prefix (optional)
- * - The cache protocol version
- * - The name of the cache
- * - The runner operating system
- * - The name of the 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
- */
-function generateCacheKey(cacheName: string): CacheKey {
-    const cacheKeyBase = `${getCacheKeyPrefix()}${CACHE_PROTOCOL_VERSION}${cacheName}`
-
-    // At the most general level, share caches for all executions on the same OS
-    const runnerOs = process.env['RUNNER_OS'] || ''
-    const cacheKeyForOs = `${cacheKeyBase}|${runnerOs}`
-
-    // Prefer caches that run this job
-    const cacheKeyForJob = `${cacheKeyForOs}|${github.context.job}`
-
-    // Prefer (even more) jobs that run this job with the same context (matrix)
-    const cacheKeyForJobContext = `${cacheKeyForJob}[${determineJobContext()}]`
-
-    // Exact match on Git SHA
-    const cacheKey = `${cacheKeyForJobContext}-${github.context.sha}`
-
-    if (core.getBooleanInput(STRICT_CACHE_MATCH_PARAMETER)) {
-        return new CacheKey(cacheKey, [cacheKeyForJobContext])
-    }
-
-    return new CacheKey(cacheKey, [cacheKeyForJobContext, cacheKeyForJob, cacheKeyForOs])
-}
 
 export class GradleStateCache {
     private cacheName: string

src/cache-utils.ts

@@ -1,17 +1,26 @@
 import * as core from '@actions/core'
 import * as cache from '@actions/cache'
+import * as github from '@actions/github'
 import * as crypto from 'crypto'
 import * as path from 'path'
 import * as fs from 'fs'
 
 import {CacheEntryListener} from './cache-reporting'
 
+const CACHE_PROTOCOL_VERSION = 'v6-'
+
 const JOB_CONTEXT_PARAMETER = 'workflow-job-context'
 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_DEBUG_VAR = 'GRADLE_BUILD_ACTION_CACHE_DEBUG_ENABLED'
-const CACHE_PREFIX_VAR = 'GRADLE_BUILD_ACTION_CACHE_KEY_PREFIX'
+
+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'
 
 export function isCacheDisabled(): boolean {
     return core.getBooleanInput(CACHE_DISABLED_PARAMETER)
@@ -29,18 +38,91 @@ export function isCacheDebuggingEnabled(): boolean {
     return process.env[CACHE_DEBUG_VAR] ? true : false
 }
 
-export function getCacheKeyPrefix(): string {
-    // Prefix can be used to force change all cache keys (defaults to cache protocol version)
-    return process.env[CACHE_PREFIX_VAR] || ''
+/**
+ * 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
+    }
 }
 
-export function determineJobContext(): string {
+/**
+ * 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 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): 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}|${getCacheKeyEnvironment()}`
+
+    // Prefer caches that run this job
+    const cacheKeyForJob = `${cacheKeyForEnvironment}|${getCacheKeyJob()}`
+
+    // Prefer (even more) jobs that run this job with the same context (matrix)
+    const cacheKeyForJobContext = `${cacheKeyForJob}[${getCacheKeyJobInstance()}]`
+
+    // Exact match on Git SHA
+    const cacheKey = `${cacheKeyForJobContext}-${getCacheKeyJobExecution()}`
+
+    if (core.getBooleanInput(STRICT_CACHE_MATCH_PARAMETER)) {
+        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 {
+    // Prefix can be used to force change all cache keys (defaults to cache protocol version)
+    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 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 workflowJobContext = core.getInput(JOB_CONTEXT_PARAMETER)
     return hashStrings([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
+}
+
 export function hashFileNames(fileNames: string[]): string {
     return hashStrings(fileNames.map(x => x.replace(new RegExp(`\\${path.sep}`, 'g'), '/')))
 }