xplat/js/react-native-github/packages/react-native/ReactAndroid/src/main/jni/react/hermes/instrumentation/HermesSamplingProfiler.cpp

packages/react-native/ReactAndroid/src/main/jni/react/hermes/instrumentation/test/HermesSamplingProfilerTest.cpp

@@ -0,0 +1,106 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include "HermesSamplingProfiler.h"
+
+#include <hermes/hermes.h>
+#include <jsi/jsi.h>
+
+#include <gtest/gtest.h>
+
+#include <cstdio>
+#include <fstream>
+#include <memory>
+#include <sstream>
+#include <string>
+#include <system_error>
+
+namespace facebook::jsi::jni {
+namespace {
+
+// The JNI entry points ignore their `jclass` argument, so a null alias_ref is
+// sufficient to drive them from a host unit test without a live JVM.
+jni::alias_ref<jclass> noClass() {
+  return jni::alias_ref<jclass>{};
+}
+
+// Creates a HermesRuntime that automatically registers itself with the global
+// sampling profiler. Without such a runtime the global profiler has nothing to
+// serialize.
+std::unique_ptr<facebook::hermes::HermesRuntime> makeProfilingRuntime() {
+  auto config = ::hermes::vm::RuntimeConfig::Builder()
+                    .withEnableSampleProfiling(true)
+                    .build();
+  auto* rootAPI = castInterface<facebook::hermes::IHermesRootAPI>(
+      facebook::hermes::makeHermesRootAPI());
+  return rootAPI->makeHermesRuntime(config);
+}
+
+std::string readFile(const std::string& path) {
+  std::ifstream stream(path, std::ios::binary);
+  std::stringstream buffer;
+  buffer << stream.rdbuf();
+  return buffer.str();
+}
+
+class HermesSamplingProfilerTest : public ::testing::Test {
+ protected:
+  std::string tracePath(const std::string& name) const {
+    return ::testing::TempDir() + "HermesSamplingProfilerTest_" + name;
+  }
+};
+
+// Enabling the profiler, dumping while a runtime is registered, then disabling
+// should forward the requested filename all the way to Hermes and write a
+// well-formed Chrome trace document to exactly that path.
+TEST_F(HermesSamplingProfilerTest, dumpWhileProfilingWritesChromeTrace) {
+  const std::string path = tracePath("profiling.json");
+  std::remove(path.c_str());
+
+  HermesSamplingProfiler::enable(noClass());
+  auto runtime = makeProfilingRuntime();
+  HermesSamplingProfiler::dumpSampledTraceToFile(noClass(), path);
+  HermesSamplingProfiler::disable(noClass());
+
+  const std::string contents = readFile(path);
+  EXPECT_NE(contents.find("traceEvents"), std::string::npos);
+  EXPECT_NE(contents.find("samples"), std::string::npos);
+  EXPECT_NE(contents.find("stackFrames"), std::string::npos);
+
+  std::remove(path.c_str());
+}
+
+// A destination that cannot be opened (its parent directory does not exist)
+// must surface the underlying I/O failure to the caller rather than being
+// swallowed.
+TEST_F(HermesSamplingProfilerTest, dumpToUnwritablePathThrows) {
+  const std::string path = ::testing::TempDir() + "hsp_missing_dir/trace.json";
+
+  EXPECT_THROW(
+      HermesSamplingProfiler::dumpSampledTraceToFile(noClass(), path),
+      std::system_error);
+}
+
+// With no runtime registered the global profiler has no data to serialize, but
+// the JNI entry point must still create the exact file it was asked to write.
+TEST_F(
+    HermesSamplingProfilerTest,
+    dumpWithoutRegisteredRuntimeCreatesEmptyFile) {
+  const std::string path = tracePath("no_runtime.json");
+  std::remove(path.c_str());
+
+  HermesSamplingProfiler::dumpSampledTraceToFile(noClass(), path);
+
+  std::ifstream stream(path, std::ios::binary);
+  ASSERT_TRUE(stream.good());
+  EXPECT_TRUE(readFile(path).empty());
+
+  std::remove(path.c_str());
+}
+
+} // namespace
+} // namespace facebook::jsi::jni