[fuchsia] Fix TestLauncher to use persistent storage for /cache.

Previously tests requiring access to /cache storage had the
isolated-cache-storage feature specified in the test suite's component
manifest. This was propagated to each test-batch process directly,
creating the possibility of concurrently executing batches conflicting
with one another. There is also a risk of the system purging all the
isolated cache directories while a test is using cache, especially if
some other test uses the CacheControl API to manually force a purge.

TestLauncher now splits the persistent data directory passed to each
test batch process to use it both as /data and /cache, thereby avoiding
clashes, or unexpected purge effects.

This workaround may be removed/replaced if the TestLauncher is updated
to launch batches as isolated components, and the component framework
updated to support deterministic cache storage for testing.

Bug: 1176165, 1242170
Change-Id: If763d28078d685bbe495a29f8c55b682077d4dfd
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3110415
Auto-Submit: Wez <wez@chromium.org>
Reviewed-by: Daniel Cheng <dcheng@chromium.org>
Commit-Queue: Wez <wez@chromium.org>
Cr-Commit-Position: refs/heads/main@{#914653}

base/test/launcher/test_launcher.cc

@@ -355,15 +355,16 @@ int LaunchChildTestProcessWithOptions(const CommandLine& command_line,
   new_options.spawn_flags = FDIO_SPAWN_CLONE_STDIO | FDIO_SPAWN_CLONE_JOB;
 
   const base::FilePath kDataPath(base::kPersistedDataDirectoryPath);
+  const base::FilePath kCachePath(base::kPersistedCacheDirectoryPath);
 
-  // Clone all namespace entries from the current process, except /data, which
-  // is overridden below.
+  // Clone all namespace entries from the current process, except /data and
+  // /cache, which are overridden below.
   fdio_flat_namespace_t* flat_namespace = nullptr;
   zx_status_t result = fdio_ns_export_root(&flat_namespace);
   ZX_CHECK(ZX_OK == result, result) << "fdio_ns_export_root";
   for (size_t i = 0; i < flat_namespace->count; ++i) {
     base::FilePath path(flat_namespace->path[i]);
-    if (path == kDataPath) {
+    if (path == kDataPath || path == kCachePath) {
       result = zx_handle_close(flat_namespace->handle[i]);
       ZX_CHECK(ZX_OK == result, result) << "zx_handle_close";
     } else {
@@ -379,25 +380,36 @@ int LaunchChildTestProcessWithOptions(const CommandLine& command_line,
   new_options.job_handle = job_handle.get();
 
   // Give this test its own isolated /data directory by creating a new temporary
-  // subdirectory under data (/data/test-$PID) and binding that to /data on the
-  // child process.
+  // subdirectory under data (/data/test-$PID) and binding paths under that to
+  // /data and /cache in the child process.
+  // Persistent data storage is mapped to /cache rather than system-provided
+  // cache storage, to avoid unexpected purges (see crbug.com/1242170).
   CHECK(base::PathExists(kDataPath));
 
   // Create the test subdirectory with a name that is unique to the child test
   // process (qualified by parent PID and an autoincrementing test process
   // index).
   static base::AtomicSequenceNumber child_launch_index;
-  base::FilePath nested_data_path = kDataPath.AppendASCII(
+  const base::FilePath child_data_path = kDataPath.AppendASCII(
       base::StringPrintf("test-%zu-%d", base::Process::Current().Pid(),
                          child_launch_index.GetNext()));
-  CHECK(!base::DirectoryExists(nested_data_path));
-  CHECK(base::CreateDirectory(nested_data_path));
-  DCHECK(base::DirectoryExists(nested_data_path));
+  CHECK(!base::DirectoryExists(child_data_path));
+  CHECK(base::CreateDirectory(child_data_path));
+  DCHECK(base::DirectoryExists(child_data_path));
 
-  // Bind the new test subdirectory to /data in the child process' namespace.
+  const base::FilePath test_data_dir(child_data_path.AppendASCII("data"));
+  CHECK(base::CreateDirectory(test_data_dir));
+  const base::FilePath test_cache_dir(child_data_path.AppendASCII("cache"));
+  CHECK(base::CreateDirectory(test_cache_dir));
+
+  // Transfer handles to the new directories as /data and /cache in the child
+  // process' namespace.
   new_options.paths_to_transfer.push_back(
       {kDataPath,
-       base::OpenDirectoryHandle(nested_data_path).TakeChannel().release()});
+       base::OpenDirectoryHandle(test_data_dir).TakeChannel().release()});
+  new_options.paths_to_transfer.push_back(
+      {kCachePath,
+       base::OpenDirectoryHandle(test_cache_dir).TakeChannel().release()});
 #endif  // defined(OS_FUCHSIA)
 
 #if defined(OS_LINUX) || defined(OS_CHROMEOS)
@@ -483,7 +495,7 @@ int LaunchChildTestProcessWithOptions(const CommandLine& command_line,
     ZX_CHECK(status == ZX_OK, status);
 
     // Cleanup the data directory.
-    CHECK(DeletePathRecursively(nested_data_path));
+    CHECK(DeletePathRecursively(child_data_path));
 #elif defined(OS_POSIX)
     // It is not possible to waitpid() on any leaked sub-processes of the test
     // batch process, since those are not direct children of this process.

base/test/launcher/test_launcher_unittest.cc

@@ -719,6 +719,15 @@ TEST_F(TestLauncherTest, TestChildTempDir) {
   EXPECT_FALSE(DirectoryExists(task_temp));
 }
 
+#if defined(OS_FUCHSIA)
+// Verifies that test processes have /data, /cache and /tmp available.
+TEST_F(TestLauncherTest, ProvidesDataCacheAndTmpDirs) {
+  EXPECT_TRUE(base::DirectoryExists(base::FilePath("/data")));
+  EXPECT_TRUE(base::DirectoryExists(base::FilePath("/cache")));
+  EXPECT_TRUE(base::DirectoryExists(base::FilePath("/tmp")));
+}
+#endif  // defined(OS_FUCHSIA)
+
 // Unit tests to validate UnitTestLauncherDelegate implementation.
 class UnitTestLauncherDelegateTester : public testing::Test {
  protected:

build/config/fuchsia/test/access_test_data_dir.test-cmx

@@ -1,7 +0,0 @@
-{
-  "sandbox": {
-    "features": [
-      "isolated-cache-storage"
-    ]
-  }
-}

fuchsia/engine/BUILD.gn

@@ -555,8 +555,6 @@ test("web_engine_unittests") {
     "//third_party/fuchsia-sdk/sdk/pkg/scenic_cpp",
   ]
   additional_manifest_fragments = [
-    "//build/config/fuchsia/test/access_test_data_dir.test-cmx",
-
     # TODO(crbug.com/1185811): Figure out why jit_capabilities is needed.
     "//build/config/fuchsia/test/jit_capabilities.test-cmx",