Tracing pre-filtering

base/trace_event/trace_event_unittest.cc

Index: base/trace_event/trace_event_unittest.cc
diff --git a/base/trace_event/trace_event_unittest.cc b/base/trace_event/trace_event_unittest.cc
index e626a779ed5e33cc5b1eb8dedac1435c0984b282..5fd62f1b5342f5fd11fd8a088367af7b5879d2a2 100644
--- a/base/trace_event/trace_event_unittest.cc
+++ b/base/trace_event/trace_event_unittest.cc
@@ -17,6 +17,7 @@
 #include "base/json/json_writer.h"
 #include "base/location.h"
 #include "base/macros.h"
+#include "base/memory/ptr_util.h"
 #include "base/memory/ref_counted_memory.h"
 #include "base/memory/singleton.h"
 #include "base/process/process_handle.h"
@@ -3099,5 +3100,100 @@ TEST_F(TraceEventTestFixture, SyntheticDelayConfigurationToString) {
   EXPECT_EQ(filter, config.ToCategoryFilterString());
 }
 
+class TestEventFilter : public TraceLog::TraceEventFilter {
+ public:
+  bool FilterTraceEvent(const TraceEvent& trace_event) const override {
+    filter_trace_event_hit_count_++;
+    return true;
+  }
+
+  void EndEvent(const char* category_group, const char* name) override {
+    end_event_hit_count_++;
+  }
+
+  static size_t filter_trace_event_hit_count() {
+    return filter_trace_event_hit_count_;
+  }
+  static size_t end_event_hit_count() { return end_event_hit_count_; }
+
+ private:
+  static size_t filter_trace_event_hit_count_;
+  static size_t end_event_hit_count_;
+};
+
+size_t TestEventFilter::filter_trace_event_hit_count_ = 0;
+size_t TestEventFilter::end_event_hit_count_ = 0;
+
+std::unique_ptr<TraceLog::TraceEventFilter> ConstructTestEventFilter() {
+  return WrapUnique(new TestEventFilter);
+}
+
+TEST_F(TraceEventTestFixture, EventFiltering) {
+  const char config_json[] =
+      "{"
+      "  \"included_categories\": ["
+      "    \"filtered_cat\","
+      "    \"unfiltered_cat\"],"
+      "  \"event_filters\": ["
+      "     {"
+      "       \"filter_predicate\": \"testing_predicate\", "
+      "       \"included_categories\": [\"*\"]"
+      "     }"
+      "    "
+      "  ]"
+      "}";
+
+  TraceLog::SetTraceEventFilterConstructorForTesting(ConstructTestEventFilter);
+  TraceConfig trace_config(config_json);
+  TraceLog::GetInstance()->SetEnabled(trace_config, TraceLog::RECORDING_MODE);
+  EXPECT_TRUE(TraceLog::GetInstance()->IsEnabled());

[Primiano Tucci (use gerrit), 2016/05/31 15:41:23]

I think you want this to be an ASSERT_TRUE. the code below doesn't make sense
otherwise.

[oystein (OOO til 10th of July), 2016/08/01 13:39:49]

Done.

+
+  TRACE_EVENT0("a cat", "a snake");

[Primiano Tucci (use gerrit), 2016/05/31 15:41:23]

Add a comment here explaining that these trace events will go out of scope after
the EndTraceAndFlush(), as opposite to "a mushroom". It was initially a bit
puzzled by seeing that apparently useless scope:
Or if you prefer, instead  of comments replace "a snake" "a mushroom" with 

TRACE_EVENT0("cat", "the end of this event will not be recorded because of its
scope")
TRACE_EVENT0("cat", "same here")

{
  TRACE_EVENT0("cat", "this one instead will be filtered on both begin and end")
}

[oystein (OOO til 10th of July), 2016/08/01 13:39:49]

Done.

+  TRACE_EVENT0("a cat", "a mushroom");
+
+  {
+    TRACE_EVENT0("a cat", "another cat whoa");
+  }
+
+  EndTraceAndFlush();
+
+  EXPECT_EQ(TestEventFilter::filter_trace_event_hit_count(), 3u);
+  EXPECT_EQ(TestEventFilter::end_event_hit_count(), 1u);
+}
+
+TEST_F(TraceEventTestFixture, EventWhitelistFiltering) {
+  const char config_json[] =
+      "{"
+      "  \"included_categories\": ["
+      "    \"filtered_cat\","
+      "    \"unfiltered_cat\"],"
+      "  \"event_filters\": ["
+      "     {"
+      "       \"filter_predicate\": \"event_whitelist_predicate\", "
+      "       \"included_categories\": [\"*\"], "
+      "       \"excluded_categories\": [\"unfiltered_cat\"], "
+      "       \"filter_args\": {"
+      "           \"event_name_whitelist\": [\"a snake\", \"a dog\"]"
+      "         }"
+      "     }"
+      "    "
+      "  ]"
+      "}";
+
+  TraceConfig trace_config(config_json);
+  TraceLog::GetInstance()->SetEnabled(trace_config, TraceLog::RECORDING_MODE);
+  EXPECT_TRUE(TraceLog::GetInstance()->IsEnabled());
+
+  TRACE_EVENT0("filtered_cat", "a snake");
+  TRACE_EVENT0("filtered_cat", "a mushroom");
+  TRACE_EVENT0("unfiltered_cat", "a cat");
+
+  EndTraceAndFlush();
+
+  EXPECT_TRUE(FindMatchingValue("name", "a snake"));
+  EXPECT_FALSE(FindMatchingValue("name", "a mushroom"));
+  EXPECT_TRUE(FindMatchingValue("name", "a cat"));
+}
+
 }  // namespace trace_event
 }  // namespace base