feat(cache): add cache-mode client behavior (read-denied warning + ACTIONS_CACHE_MODE skip) (#2447)

* feat(cache): surface cache read-denied as a distinct restore warning

Mirror the existing cache write-denied handling on the restore path. When
the receiver refuses a download URL because the run's token has no readable
cache scopes, it returns a twirp PermissionDenied (HTTP 403). The twirp
client wraps that 403 in a generic Error, so the stable 'cache read denied:'
prefix is embedded in the message rather than at the start.

- Add CACHE_READ_DENIED_PREFIX and CacheReadDeniedError
- Dispatch on the prefix in the restoreCacheV2 catch block (V2 only), log a
  policy-specific warning, and report a cache miss so the run continues
- Add a test mirroring the write-denied coverage

* chore(cache): trim comments, bump to 6.2.0, add RELEASES entry

* refactor(cache): dispatch read-denied by error name to mirror write path

Re-throw CacheReadDeniedError from an inner try/catch around
GetCacheEntryDownloadURL and dispatch on typedError.name in the outer catch,
matching how saveCacheV2 handles CacheWriteDeniedError.

* feat(cache): handle read-denied on the v1 restore path

Extend the read-denied handling to Cache Service v1 so GHES (which forces v1
via _apis/artifactcache) is covered when read-scope enforcement ships there.

- Surface the receiver's error body message from getCacheEntry instead of a
  generic status-code error, so the cache read denied: prefix reaches callers
- Re-throw CacheReadDeniedError from restoreCacheV1 and dispatch on it in the
  outer catch, mirroring restoreCacheV2 and the write-denied v1 handling
- Add a v1 read-denied test

* refactor(cache): only surface receiver body for read-denied on v1

* test(cache): assert getCacheEntry only surfaces body for read-denied

* test(cache): cover non-read-denied getCacheEntry passthrough on v1

* refactor(cache): share read-denied prefix via constants to avoid drift

* feat(cache): skip restore/save per ACTIONS_CACHE_MODE

* test(cache): expand ACTIONS_CACHE_MODE skip coverage across v1/v2 and unknown modes

* fix copilot pr feedback

Co-authored-by: Copilot Autofix powered by AI <[email protected]>

* docs(cache): remove internal reference from cache-mode comment

* test(cache): merge redundant cache-mode skip tests and simplify read-denied handling

Address PR review feedback:
- Merge the duplicate restore/save skip test.each blocks into single blocks parametrized over ACTIONS_CACHE_SERVICE_V2.
- Drop the redundant CacheReadDeniedError catch arms; the typed error is not an HttpClientError so it already falls through to a non-fatal warning.
- Clarify why read-denied classification happens both in getCacheEntry and cache.ts (dependency-free internal module cannot import the typed error).

* refactor(cache): drop redundant CacheWriteDeniedError catch arms

Mirror the read-denied simplification on the save path. CacheWriteDeniedError
is not an HttpClientError and its name does not match the ReserveCacheError
arm, so it falls through to the same non-fatal warning. Logging behavior is
unchanged (warns, never fails the run) and the exported type is still thrown
internally for consumers and tests. Also refresh stale doc wording.

* test(cache): collapse redundant restore getCacheEntry-failure tests

The two restoreCache tests exercised the identical warning + cache-miss path
now that read-denied is no longer reclassified in the catch, so merge them into
one. The read-denied prefix detection that actually branches on the message is
covered by getCacheEntry tests in cacheHttpClient.test.ts.

---------

Co-authored-by: Copilot Autofix powered by AI <[email protected]>

packages/cache/__tests__/saveCache.test.ts

@@ -35,6 +35,18 @@ beforeAll(() => {
   jest.spyOn(cacheUtils, 'createTempDirectory').mockImplementation(async () => {
     return Promise.resolve('/foo/bar')
   })
+  // config is auto-mocked; use the real cache-mode helpers so gating reflects
+  // ACTIONS_CACHE_MODE and unset stays permissive.
+  const actualConfig = jest.requireActual('../src/internal/config')
+  jest
+    .spyOn(config, 'getCacheMode')
+    .mockImplementation(actualConfig.getCacheMode)
+  jest
+    .spyOn(config, 'isCacheReadable')
+    .mockImplementation(actualConfig.isCacheReadable)
+  jest
+    .spyOn(config, 'isCacheWritable')
+    .mockImplementation(actualConfig.isCacheWritable)
 })
 
 test('save with missing input should fail', async () => {
@@ -45,6 +57,75 @@ test('save with missing input should fail', async () => {
   )
 })
 
+describe('save cache-mode gating', () => {
+  const originalMode = process.env.ACTIONS_CACHE_MODE
+  const originalV2 = process.env.ACTIONS_CACHE_SERVICE_V2
+
+  const restoreEnv = (key: string, value: string | undefined): void => {
+    if (value === undefined) {
+      delete process.env[key]
+    } else {
+      process.env[key] = value
+    }
+  }
+
+  afterEach(() => {
+    restoreEnv('ACTIONS_CACHE_MODE', originalMode)
+    restoreEnv('ACTIONS_CACHE_SERVICE_V2', originalV2)
+  })
+
+  // The skip short-circuits before v1/v2 dispatch, so it applies regardless of
+  // the ACTIONS_CACHE_SERVICE_V2 feature flag.
+  test.each([
+    ['read', undefined],
+    ['read', 'true'],
+    ['none', undefined],
+    ['none', 'true']
+  ])(
+    "mode '%s' skips save with ACTIONS_CACHE_SERVICE_V2=%s",
+    async (mode, v2) => {
+      process.env.ACTIONS_CACHE_MODE = mode
+      restoreEnv('ACTIONS_CACHE_SERVICE_V2', v2)
+      const logInfoMock = jest.spyOn(core, 'info')
+      const resolvePathsMock = jest.spyOn(cacheUtils, 'resolvePaths')
+
+      const cacheId = await saveCache(['node_modules'], 'node-test')
+
+      expect(cacheId).toBe(-1)
+      expect(resolvePathsMock).not.toHaveBeenCalled()
+      expect(logInfoMock).toHaveBeenCalledTimes(1)
+      expect(logInfoMock).toHaveBeenCalledWith(
+        `Cache save skipped: the effective cache-mode '${mode}' does not permit writes.`
+      )
+    }
+  )
+
+  test.each(['write', 'write-only', '', 'garbage'])(
+    "mode '%s' does not skip save",
+    async mode => {
+      if (mode === '') {
+        delete process.env.ACTIONS_CACHE_MODE
+      } else {
+        process.env.ACTIONS_CACHE_MODE = mode
+      }
+      const logInfoMock = jest.spyOn(core, 'info')
+      const resolvePathsMock = jest.spyOn(cacheUtils, 'resolvePaths')
+
+      try {
+        await saveCache(['node_modules'], 'node-test')
+      } catch {
+        // Downstream client is not fully mocked here; we only assert the guard
+        // let execution proceed past it.
+      }
+
+      expect(resolvePathsMock).toHaveBeenCalled()
+      expect(logInfoMock).not.toHaveBeenCalledWith(
+        expect.stringContaining('Cache save skipped')
+      )
+    }
+  )
+})
+
 test('save with large cache outputs should fail', async () => {
   const filePath = 'node_modules'
   const primaryKey = 'Linux-node-bb828da54c148048dd17899ba9fda624811cfb43'