Introduce a new framework for back-and-forth tracked/protected preferences migration.

base/prefs/json_pref_store_unittest.cc

Index: base/prefs/json_pref_store_unittest.cc
diff --git a/base/prefs/json_pref_store_unittest.cc b/base/prefs/json_pref_store_unittest.cc
index f4e1e5190dd903bb4c69ffab8f0d003106f987c0..4c9c847708f5f2d3f9845759bfffb7598b68e832 100644
--- a/base/prefs/json_pref_store_unittest.cc
+++ b/base/prefs/json_pref_store_unittest.cc
@@ -4,10 +4,12 @@
 
 #include "base/prefs/json_pref_store.h"
 
+#include "base/bind.h"
 #include "base/file_util.h"
 #include "base/files/scoped_temp_dir.h"
 #include "base/memory/ref_counted.h"
 #include "base/memory/scoped_ptr.h"
+#include "base/message_loop/message_loop.h"
 #include "base/path_service.h"
 #include "base/prefs/pref_filter.h"
 #include "base/run_loop.h"
@@ -25,6 +27,50 @@ namespace {
 
 const char kHomePage[] = "homepage";
 
+// A PrefFilter that will intercept all calls to FilterOnLoad() and hold on
+// to the |prefs| until explicitly asked to release them.
+class InterceptingPrefFilter : public PrefFilter {
+ public:
+  InterceptingPrefFilter();
+  virtual ~InterceptingPrefFilter();
+
+  // PrefFilter implementation:
+  virtual void FilterOnLoad(
+      const PostFilterOnLoadCallback& post_filter_on_load_callback,
+      scoped_ptr<base::DictionaryValue> pref_store_contents) OVERRIDE;
+  virtual void FilterUpdate(const std::string& path) OVERRIDE {}
+  virtual void FilterSerializeData(
+      const base::DictionaryValue* pref_store_contents) OVERRIDE {}
+
+  bool has_intercepted_prefs() const { return intercepted_prefs_ != NULL; }
+
+  // Finalize an intercepted read, handing |intercept_prefs_| back to its
+  // JsonPrefStore.
+  void ReleasePrefs();
+
+ private:
+  PostFilterOnLoadCallback post_filter_on_load_callback_;
+  scoped_ptr<base::DictionaryValue> intercepted_prefs_;
+
+  DISALLOW_COPY_AND_ASSIGN(InterceptingPrefFilter);
+};
+
+InterceptingPrefFilter::InterceptingPrefFilter() {}
+InterceptingPrefFilter::~InterceptingPrefFilter() {}
+
+void InterceptingPrefFilter::FilterOnLoad(
+    const PostFilterOnLoadCallback& post_filter_on_load_callback,
+    scoped_ptr<base::DictionaryValue> pref_store_contents) {
+  post_filter_on_load_callback_ = post_filter_on_load_callback;
+  intercepted_prefs_ = pref_store_contents.Pass();
+}
+
+void InterceptingPrefFilter::ReleasePrefs() {
+  EXPECT_FALSE(post_filter_on_load_callback_.is_null());
+  post_filter_on_load_callback_.Run(intercepted_prefs_.Pass(), false);
+  post_filter_on_load_callback_.Reset();
+}
+
 class MockPrefStoreObserver : public PrefStore::Observer {
  public:
   MOCK_METHOD1(OnPrefValueChanged, void (const std::string&));
@@ -48,6 +94,13 @@ class JsonPrefStoreTest : public testing::Test {
     ASSERT_TRUE(PathExists(data_dir_));
   }
 
+  virtual void TearDown() OVERRIDE {
+    // Make sure all pending tasks have been processed (e.g., deleting the
+    // JsonPrefStore may post write tasks).
+    message_loop_.PostTask(FROM_HERE, MessageLoop::QuitWhenIdleClosure());
+    message_loop_.Run();
+  }
+
   // The path to temporary directory used to contain the test operations.
   base::ScopedTempDir temp_dir_;
   // The path to the directory where the test data is stored.
@@ -157,7 +210,7 @@ void RunBasicJsonPrefStoreTest(JsonPrefStore* pref_store,
 
 TEST_F(JsonPrefStoreTest, Basic) {
   ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
-                                  temp_dir_.path().AppendASCII("write.json")));
+                             temp_dir_.path().AppendASCII("write.json")));
 
   // Test that the persistent value can be loaded.
   base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
@@ -167,7 +220,8 @@ TEST_F(JsonPrefStoreTest, Basic) {
       message_loop_.message_loop_proxy().get(),
       scoped_ptr<PrefFilter>());
   ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_NONE, pref_store->ReadPrefs());
-  ASSERT_FALSE(pref_store->ReadOnly());
+  EXPECT_FALSE(pref_store->ReadOnly());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
 
   // The JSON file looks like this:
   // {
@@ -185,7 +239,7 @@ TEST_F(JsonPrefStoreTest, Basic) {
 
 TEST_F(JsonPrefStoreTest, BasicAsync) {
   ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
-                                  temp_dir_.path().AppendASCII("write.json")));
+                             temp_dir_.path().AppendASCII("write.json")));
 
   // Test that the persistent value can be loaded.
   base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
@@ -208,7 +262,8 @@ TEST_F(JsonPrefStoreTest, BasicAsync) {
     RunLoop().RunUntilIdle();
     pref_store->RemoveObserver(&mock_observer);
 
-    ASSERT_FALSE(pref_store->ReadOnly());
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_TRUE(pref_store->IsInitializationComplete());
   }
 
   // The JSON file looks like this:
@@ -301,4 +356,117 @@ TEST_F(JsonPrefStoreTest, AsyncNonExistingFile) {
   EXPECT_FALSE(pref_store->ReadOnly());
 }
 
+TEST_F(JsonPrefStoreTest, ReadWithInterceptor) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+
+  scoped_ptr<InterceptingPrefFilter> intercepting_pref_filter(
+      new InterceptingPrefFilter());
+  InterceptingPrefFilter* raw_intercepting_pref_filter_ =
+      intercepting_pref_filter.get();
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file,
+                        message_loop_.message_loop_proxy().get(),
+                        intercepting_pref_filter.PassAs<PrefFilter>());
+
+  ASSERT_EQ(PersistentPrefStore::PREF_READ_ERROR_ASYNCHRONOUS_TASK_INCOMPLETE,
+            pref_store->ReadPrefs());
+  EXPECT_FALSE(pref_store->ReadOnly());
+
+  // The store shouldn't be considered initialized until the interceptor
+  // returns.
+  EXPECT_TRUE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+  EXPECT_FALSE(pref_store->IsInitializationComplete());
+  EXPECT_FALSE(pref_store->GetValue(kHomePage, NULL));
+
+  raw_intercepting_pref_filter_->ReleasePrefs();
+
+  EXPECT_FALSE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+  EXPECT_TRUE(pref_store->IsInitializationComplete());
+  EXPECT_TRUE(pref_store->GetValue(kHomePage, NULL));
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
+TEST_F(JsonPrefStoreTest, ReadAsyncWithInterceptor) {
+  ASSERT_TRUE(base::CopyFile(data_dir_.AppendASCII("read.json"),
+                             temp_dir_.path().AppendASCII("write.json")));
+
+  // Test that the persistent value can be loaded.
+  base::FilePath input_file = temp_dir_.path().AppendASCII("write.json");
+  ASSERT_TRUE(PathExists(input_file));
+
+  scoped_ptr<InterceptingPrefFilter> intercepting_pref_filter(
+      new InterceptingPrefFilter());
+  InterceptingPrefFilter* raw_intercepting_pref_filter_ =
+      intercepting_pref_filter.get();
+  scoped_refptr<JsonPrefStore> pref_store =
+      new JsonPrefStore(input_file,
+                        message_loop_.message_loop_proxy().get(),
+                        intercepting_pref_filter.PassAs<PrefFilter>());
+
+  MockPrefStoreObserver mock_observer;
+  pref_store->AddObserver(&mock_observer);
+
+  // Ownership of the |mock_error_delegate| is handed to the |pref_store| below.
+  MockReadErrorDelegate* mock_error_delegate = new MockReadErrorDelegate;
+
+  {
+    pref_store->ReadPrefsAsync(mock_error_delegate);
+
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(0);
+    // EXPECT_CALL(*mock_error_delegate,
+    //             OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+    RunLoop().RunUntilIdle();
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_TRUE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+    EXPECT_FALSE(pref_store->IsInitializationComplete());
+    EXPECT_FALSE(pref_store->GetValue(kHomePage, NULL));
+  }
+
+  {
+    EXPECT_CALL(mock_observer, OnInitializationCompleted(true)).Times(1);
+    // EXPECT_CALL(*mock_error_delegate,
+    //             OnError(PersistentPrefStore::PREF_READ_ERROR_NONE)).Times(0);
+
+    raw_intercepting_pref_filter_->ReleasePrefs();
+
+    EXPECT_FALSE(pref_store->ReadOnly());
+    EXPECT_FALSE(raw_intercepting_pref_filter_->has_intercepted_prefs());
+    EXPECT_TRUE(pref_store->IsInitializationComplete());
+    EXPECT_TRUE(pref_store->GetValue(kHomePage, NULL));
+  }
+
+  pref_store->RemoveObserver(&mock_observer);
+
+  // The JSON file looks like this:
+  // {
+  //   "homepage": "http://www.cnn.com",
+  //   "some_directory": "/usr/local/",
+  //   "tabs": {
+  //     "new_windows_in_tabs": true,
+  //     "max_tabs": 20
+  //   }
+  // }
+
+  RunBasicJsonPrefStoreTest(
+      pref_store.get(), input_file, data_dir_.AppendASCII("write.golden.json"));
+}
+
 }  // namespace base