Currently, ExUnit/CaptureLog.capture_log/2 returns the logs content captured but offers no possibility of returning any other result.

This makes it difficult to execute some_function we know should emit a log and both assert the log content and use the result of some_function.

One alternative is using the result within the function passed to capture_log, but that doesn’t compose well, or nest, and is problematic as the rest of the code could generate warnings, etc.

Another way is uses the Process dictionary, but that’s pretty ugly:

  def with_log_matching(match, fun) do
    assert ExUnit.CaptureLog.capture_log(fn ->
      result = fun.()
      Process.put(:log_capture_function_result, result)
    end) =~ match
    Process.delete(:log_capture_function_result)
  end

  test "something" do
    result = with_log_matching("Hey, something strange is going on", fn ->
      do_something_and_return(...)
    end

    assert do_something_else(result) == :ok
  end

Could we have either a new function capture_log_and_result, or else a new option for capture_log like with_result: true or similar that would return {result, "captured log..."} instead of just the captured log?