Enable base::Value::Dict and base::Value::List to be used with tracing.

Change-Id: Ic0cb35a53cfa179f2fbb5b82819c8fd0fe5d82da
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/3696804
Reviewed-by: Matt Menke <mmenke@chromium.org>
Commit-Queue: Daniel Cheng <dcheng@chromium.org>
Reviewed-by: Alexander Timin <altimin@chromium.org>
Cr-Commit-Position: refs/heads/main@{#1012560}

base/values.cc

@@ -789,6 +789,13 @@ std::string Value::Dict::DebugString() const {
   return DebugStringImpl(*this);
 }
 
+void Value::Dict::WriteIntoTrace(perfetto::TracedValue context) const {
+  perfetto::TracedDictionary dict = std::move(context).WriteDictionary();
+  for (auto kv : *this) {
+    dict.Add(perfetto::DynamicString(kv.first), kv.second);
+  }
+}
+
 Value::Dict::Dict(
     const flat_map<std::string, std::unique_ptr<Value>>& storage) {
   storage_.reserve(storage.size());
@@ -992,6 +999,13 @@ std::string Value::List::DebugString() const {
   return DebugStringImpl(*this);
 }
 
+void Value::List::WriteIntoTrace(perfetto::TracedValue context) const {
+  perfetto::TracedArray array = std::move(context).WriteArray();
+  for (const auto& item : *this) {
+    array.Append(item);
+  }
+}
+
 Value::List::List(const std::vector<Value>& storage) {
   storage_.reserve(storage.size());
   for (const auto& value : storage) {
@@ -1522,38 +1536,26 @@ std::string Value::DebugString() const {
 
 #if BUILDFLAG(ENABLE_BASE_TRACING)
 void Value::WriteIntoTrace(perfetto::TracedValue context) const {
-  switch (type()) {
+  Visit([&](const auto& member) {
-    case Type::BOOLEAN:
+    using T = std::decay_t<decltype(member)>;
-      std::move(context).WriteBoolean(GetBool());
+    if constexpr (std::is_same_v<T, absl::monostate>) {
-      return;
-    case Type::INTEGER:
-      std::move(context).WriteInt64(GetInt());
-      return;
-    case Type::DOUBLE:
-      std::move(context).WriteDouble(GetDouble());
-      return;
-    case Type::STRING:
-      std::move(context).WriteString(GetString());
-      return;
-    case Type::BINARY:
-      std::move(context).WriteString("<binary data not supported>");
-      return;
-    case Type::DICTIONARY: {
-      perfetto::TracedDictionary dict = std::move(context).WriteDictionary();
-      for (auto kv : DictItems())
-        dict.Add(perfetto::DynamicString{kv.first}, kv.second);
-      return;
-    }
-    case Type::LIST: {
-      perfetto::TracedArray array = std::move(context).WriteArray();
-      for (const auto& item : GetListDeprecated())
-        array.Append(item);
-      return;
-    }
-    case Type::NONE:
       std::move(context).WriteString("<none>");
-      return;
+    } else if constexpr (std::is_same_v<T, bool>) {
-  }
+      std::move(context).WriteBoolean(member);
+    } else if constexpr (std::is_same_v<T, int>) {
+      std::move(context).WriteInt64(member);
+    } else if constexpr (std::is_same_v<T, DoubleStorage>) {
+      std::move(context).WriteDouble(member);
+    } else if constexpr (std::is_same_v<T, std::string>) {
+      std::move(context).WriteString(member);
+    } else if constexpr (std::is_same_v<T, BlobStorage>) {
+      std::move(context).WriteString("<binary data not supported>");
+    } else if constexpr (std::is_same_v<T, Dict>) {
+      member.WriteIntoTrace(std::move(context));
+    } else if constexpr (std::is_same_v<T, List>) {
+      member.WriteIntoTrace(std::move(context));
+    }
+  });
 }
 #endif  // BUILDFLAG(ENABLE_BASE_TRACING)
 

base/values.h

@@ -521,6 +521,11 @@ class BASE_EXPORT GSL_OWNER Value {
     // Serializes to a string for logging and debug purposes.
     std::string DebugString() const;
 
+#if BUILDFLAG(ENABLE_BASE_TRACING)
+    // Write this object into a trace.
+    void WriteIntoTrace(perfetto::TracedValue) const;
+#endif  // BUILDFLAG(ENABLE_BASE_TRACING)
+
    private:
     BASE_EXPORT friend bool operator==(const Dict& lhs, const Dict& rhs);
     BASE_EXPORT friend bool operator!=(const Dict& lhs, const Dict& rhs);
@@ -638,6 +643,11 @@ class BASE_EXPORT GSL_OWNER Value {
     // Serializes to a string for logging and debug purposes.
     std::string DebugString() const;
 
+#if BUILDFLAG(ENABLE_BASE_TRACING)
+    // Write this object into a trace.
+    void WriteIntoTrace(perfetto::TracedValue) const;
+#endif  // BUILDFLAG(ENABLE_BASE_TRACING)
+
    private:
     BASE_EXPORT friend bool operator==(const List& lhs, const List& rhs);
     BASE_EXPORT friend bool operator!=(const List& lhs, const List& rhs);

base/values_unittest.cc

@@ -2497,14 +2497,18 @@ TEST(ValuesTest, TracingSupport) {
   EXPECT_EQ(perfetto::TracedValueToString(Value("value")), "value");
   EXPECT_EQ(perfetto::TracedValueToString(Value(Value::Type::NONE)), "<none>");
   {
-    Value::ListStorage list;
+    Value::List list;
-    list.emplace_back(2);
+    EXPECT_EQ(perfetto::TracedValueToString(list), "{}");
-    list.emplace_back(3);
+    list.Append(2);
-    EXPECT_EQ(perfetto::TracedValueToString(Value(list)), "[2,3]");
+    list.Append(3);
+    EXPECT_EQ(perfetto::TracedValueToString(list), "[2,3]");
+    EXPECT_EQ(perfetto::TracedValueToString(Value(std::move(list))), "[2,3]");
   }
   {
     Value::Dict dict;
+    EXPECT_EQ(perfetto::TracedValueToString(dict), "{}");
     dict.Set("key", "value");
+    EXPECT_EQ(perfetto::TracedValueToString(dict), "{key:value}");
     EXPECT_EQ(perfetto::TracedValueToString(Value(std::move(dict))),
               "{key:value}");
   }