[Localization] Add localization serialization tests

1. YAML <-> DB format + verification
2. Empty DB to write/read and fallback verification
3. Random holes in the DB file test write/read and fallback

Author: xedin

unittests/Localization/CMakeLists.txt

@@ -1,5 +1,6 @@
 add_swift_unittest(swiftLocalizationTests
-  DefToYAMLConverterTests.cpp)
+  DefToYAMLConverterTests.cpp
+  SerializationTests.cpp)
 
 target_link_libraries(swiftLocalizationTests
   PRIVATE

unittests/Localization/SerializationTests.cpp

@@ -0,0 +1,113 @@
+//===--- LocalizationProducerTests.cpp -------------------------------------===//
+//
+// This source file is part of the Swift.org open source project
+//
+// Copyright (c) 2014 - 2020 Apple Inc. and the Swift project authors
+// Licensed under Apache License v2.0 with Runtime Library Exception
+//
+// See https://swift.org/LICENSE.txt for license information
+// See https://swift.org/CONTRIBUTORS.txt for the list of Swift project authors
+//
+//===----------------------------------------------------------------------===//
+
+#include "LocalizationTest.h"
+#include "swift/Localization/LocalizationFormat.h"
+#include "llvm/ADT/SmallBitVector.h"
+#include "llvm/ADT/StringRef.h"
+#include "llvm/Support/FileSystem.h"
+#include "llvm/Support/MemoryBuffer.h"
+#include "llvm/Support/raw_ostream.h"
+#include "gtest/gtest.h"
+#include <string>
+#include <random>
+
+using namespace swift::diag;
+using namespace swift::unittests;
+
+TEST_F(LocalizationTest, TestYAMLSerialization) {
+  YAMLLocalizationProducer yaml(YAMLPath);
+
+  auto dbFile = createTemporaryFile("en", "db");
+
+  // First, let's serialize English translations
+  {
+    SerializedLocalizationWriter writer;
+
+    yaml.forEachAvailable([&writer](swift::DiagID id, llvm::StringRef translation) {
+                            writer.insert(id, translation);
+                          });
+
+    ASSERT_FALSE(writer.emit(dbFile));
+  }
+
+  // Now, let's make sure that serialized version matches "source" YAML
+  auto dbContent = llvm::MemoryBuffer::getFile(dbFile);
+  ASSERT_TRUE(dbContent);
+
+  SerializedLocalizationProducer db(std::move(dbContent.get()));
+  yaml.forEachAvailable([&db](swift::DiagID id, llvm::StringRef translation) {
+    ASSERT_EQ(translation, db.getMessageOr(id, "<no-fallback>"));
+  });
+}
+
+TEST_F(LocalizationTest, TestSerializationOfEmptyFile) {
+  auto dbFile = createTemporaryFile("by", "db");
+  SerializedLocalizationWriter writer;
+  ASSERT_FALSE(writer.emit(dbFile));
+
+  YAMLLocalizationProducer yaml(YAMLPath);
+
+  // Reading of the empty `db` file should always return default message.
+  {
+    auto dbContent = llvm::MemoryBuffer::getFile(dbFile);
+    ASSERT_TRUE(dbContent);
+
+    SerializedLocalizationProducer db(std::move(dbContent.get()));
+    yaml.forEachAvailable([&db](swift::DiagID id, llvm::StringRef translation) {
+      ASSERT_EQ("<<<default-fallback>>>",
+                db.getMessageOr(id, "<<<default-fallback>>>"));
+    });
+  }
+}
+
+TEST_F(LocalizationTest, TestSerializationWithGaps) {
+  // Initially all of the messages are included.
+  llvm::SmallBitVector includedMessages(LocalDiagID::NumDiags, true);
+
+  // Let's punch some holes in the diagnostic content.
+  for (unsigned i = 0, n = 200; i != n; ++i) {
+    unsigned position = RandNumber(LocalDiagID::NumDiags);
+    includedMessages.flip(position);
+  }
+
+  YAMLLocalizationProducer yaml(YAMLPath);
+  auto dbFile = createTemporaryFile("en", "db");
+
+  {
+    SerializedLocalizationWriter writer;
+
+    yaml.forEachAvailable([&](swift::DiagID id, llvm::StringRef translation) {
+      if (includedMessages.test((unsigned)id))
+        writer.insert(id, translation);
+    });
+
+    ASSERT_FALSE(writer.emit(dbFile));
+  }
+
+
+  {
+    auto dbContent = llvm::MemoryBuffer::getFile(dbFile);
+    ASSERT_TRUE(dbContent);
+
+    SerializedLocalizationProducer db(std::move(dbContent.get()));
+    yaml.forEachAvailable([&](swift::DiagID id, llvm::StringRef translation) {
+      auto position = (unsigned)id;
+
+      std::string expectedMessage = includedMessages.test(position)
+                                        ? std::string(translation)
+                                        : "<<<default-fallback>>>";
+
+      ASSERT_EQ(expectedMessage, db.getMessageOr(id, "<<<default-fallback>>>"));
+    });
+  }
+}