[FR] support flag --benchmark_list_tests work with --benchmark-format=json

[ylxxwx]

Is your feature request related to a problem? Please describe. For automation to collection the benchmark list easily, it is better to support use --benchmark_list_tests together with --benchmark-format=json.

Describe the solution you'd like to output the benchmark list in json format.

Describe alternatives you've considered

Additional context Add any other context or screenshots about the feature request here.

[varshneydevansh]

In this one do, we have to modify the behavior of RunSpecifiedBenchmarks to support outputting the list of benchmarks in JSON format when using the--benchmark_list_tests flag with --benchmark_format=json.

https://github.com/google/benchmark/blob/cbecc8ffc774d22b59d7ca2073827246807a5805/src/benchmark.cc#L540

In file bennchmark.cc and need some modification in the benchmark.h?

---

https://github.com/varshneydevansh/benchmark/blob/cbecc8ffc774d22b59d7ca2073827246807a5805/src/benchmark.cc#L595

  if (FLAGS_benchmark_list_tests) {
    if (FLAGS_benchmark_format == "json") {
      // is this the palce to modify?
    } else {
      for (auto const& benchmark : benchmarks)
        Out << benchmark.name().str() << "\n";
    }
  } else {
    internal::RunBenchmarks(benchmarks, display_reporter, file_reporter);
  }

[dmah42]

the test lists are a bit of a hack right now, and don't use the reporters at all. as such, i think you'll need to create a new List method in BenchmarkReporter which takes the vector of BenchmarkInstance objects and correctly prints them.

[varshneydevansh]

This is what I added in the benchmark.h file -

// Interface for custom benchmark result printers.
// By default, benchmark reports are printed to stdout. However an application
// can control the destination of the reports by calling
// RunSpecifiedBenchmarks and passing it a custom reporter object.
// The reporter object must implement the following interface.
class BENCHMARK_EXPORT BenchmarkReporter {
 public:
//Remaining code
  /**
   * @brief Lists and describes the provided benchmarks.
   *
   * This virtual method is intended to be overridden by derived classes
   * to provide specific implementations for listing benchmarks.
   * It can be used for outputting, logging, or any other operation
   * needed to handle or display the benchmarks' names and metadata.
   *
   * @param benchmarks A vector containing names and details of benchmarks
   *                   that need to be listed or processed.
   */
  virtual void BenchmarksList(const std::vector<BenchmarkName>& benchmarks) = 0;

 private:
  std::ostream* output_stream_;
  std::ostream* error_stream_;
};

---

Now my question is about the implementation of this function, do I add that in the json_reporter.cc file or create a separate file so that in future ConsoleReporter or the deprecated CSVReporter can utilize this?

[dmah42]

nit: it should be List not BenchmarksList .. we don't need the redundant naming.

the implementation would be in all the *_reporter.cc files. the existing loop -> Out implementation in benchmark.cc would go in the console_reporter.cc implementation, a new JSON one in JSON, and a "not implemented" error in the CSV one.

[varshneydevansh]

Tho I made the all changes which we are desiring -

example -

void JSONReporter::List(const std::vector<internal::BenchmarkInstance>& benchmarks) {
  std::ostream& Out = GetOutputStream();
  Out << "{\n  \"benchmarks\": [\n";

  for (size_t i = 0; i < benchmarks.size(); ++i) {
    Out << "    {\"name\": \"" << benchmarks[i].str() << "\"}";
    if (i != benchmarks.size() - 1) Out << ",";
    Out << "\n";
  }

  Out << "  ]\n}";
}

BENCHMARK_EXPORT
void ConsoleReporter::List(const std::vector<internal::BenchmarkInstance>& benchmarks) {
  std::ostream& Out = GetOutputStream();
  for (const auto& benchmark : benchmarks) {
    Out << benchmark.str() << "\n";
  }
}

void CSVReporter::List(std::vector<internal::BenchmarkInstance>& benchmarks){
    (void)benchmarks; // This is to prevent unused variable warning
    std::ostream& err = GetErrorStream();
    err << "List() method is not implemented for CSVReporter.\n";
}

in Benchmark.cc

  if (FLAGS_benchmark_list_tests) {
    if (FLAGS_benchmark_format == "json") {
      JSONReporter().List(benchmarks);
        } else {
      for (auto const& benchmark : benchmarks)
        Out << benchmark.name().str() << "\n";
    }
  } else {
    internal::RunBenchmarks(benchmarks, display_reporter, file_reporter);
  }

  return benchmarks.size();
}

But stuck to some errors. Maybe will try to do in the morning.

https://github.com/varshneydevansh/benchmark/blob/cbecc8ffc774d22b59d7ca2073827246807a5805/src/benchmark_register.cc#L197

https://github.com/varshneydevansh/benchmark/blob/cbecc8ffc774d22b59d7ca2073827246807a5805/src/benchmark.cc

[varshneydevansh]

virtual void BenchmarksList(const std::vector& benchmarks) = 0;

I made this into static void List(const std::vector<internal::BenchmarkInstance>& benchmarks);

because from the benchmark.cc it was giving error so modified the code to below -

  if (FLAGS_benchmark_list_tests) {
    if (FLAGS_benchmark_format == "json") {
      dynamic_cast<JSONReporter*>(display_reporter)->List(benchmarks);
        } else {
      //ConsoleReporter::List(benchmarks);
      dynamic_cast<ConsoleReporter*>(display_reporter)->List(benchmarks);
    }
  } else {
    internal::RunBenchmarks(benchmarks, display_reporter, file_reporter);
  }

I will look into this in the morning. Opening the PR so that you can better guide me over there.