Add option to output messages in JSON format (#288)

Signed-off-by: Addisu Z. Taddese <[email protected]>

src/cmd/ign.cc

@@ -17,6 +17,7 @@
 
 #include <chrono>
 #include <functional>
+#include <google/protobuf/util/json_util.h>
 #include <iostream>
 #include <string>
 #include <vector>
@@ -251,7 +252,7 @@ extern "C" void cmdServiceReq(const char *_service,
 
 //////////////////////////////////////////////////
 extern "C" void cmdTopicEcho(const char *_topic,
-  const double _duration, int _count)
+  const double _duration, int _count, MsgOutputFormat _outputFormat)
 {
   if (!_topic || std::string(_topic).empty())
   {
@@ -266,7 +267,23 @@ extern "C" void cmdTopicEcho(const char *_topic,
   std::function<void(const ProtoMsg&)> cb = [&](const ProtoMsg &_msg)
   {
     std::lock_guard<std::mutex> lock(mutex);
-    std::cout << _msg.DebugString() << std::endl;
+    switch (_outputFormat)
+    {
+      case MsgOutputFormat::kDefault:
+      case MsgOutputFormat::kDebugString:
+        std::cout << _msg.DebugString() << std::endl;
+        break;
+      case MsgOutputFormat::kJSON:
+        {
+          std::string jsonStr;
+          google::protobuf::util::MessageToJsonString(_msg, &jsonStr);
+          std::cout << jsonStr << std::endl;
+        }
+        break;
+      default:
+        std::cerr << "Invalid output format selected.\n";
+        return;
+    }
     ++count;
     condition.notify_one();
   };

src/cmd/ign.hh

@@ -63,6 +63,21 @@ extern "C" void cmdServiceReq(const char *_service,
                                                          const int _timeout,
                                                          const char *_reqData);
 
+extern "C" {
+  /// \brief Enum used for specifing the message output format for functions
+  /// like cmdTopicEcho.
+  enum class MsgOutputFormat {
+    // Default. Currently, this is Protobuf's DebugString output format.
+    kDefault,
+
+    // Output format used in Protobuf's Message::DebugString.
+    kDebugString,
+
+    // JSON output.
+    kJSON
+  };
+}
+
 /// \brief External hook to execute 'ign topic -e' from the command line.
 /// The _duration parameter overrides the _count parameter.
 /// \param[in] _topic Topic name.
@@ -71,9 +86,9 @@ extern "C" void cmdServiceReq(const char *_service,
 /// \param[in] _count Number of messages to echo and then stop. A value <= 0
 /// indicates no limit. The _duration parameter overrides the _count
 /// parameter.
-extern "C" void cmdTopicEcho(const char *_topic,
-                                                        const double _duration,
-                                                        int _count);
+/// \param[in] _outputFormat Message output format.
+extern "C" void cmdTopicEcho(const char *_topic, const double _duration,
+                             int _count, MsgOutputFormat _outputFormat);
 
 /// \brief External hook to read the library version.
 /// \return C-string representing the version. Ex.: 0.1.2

src/cmd/ign_src_TEST.cc

@@ -15,6 +15,7 @@
  *
 */
 
+#include <future>
 #include <string>
 #include <iostream>
 #include <sstream>
@@ -230,17 +231,56 @@ TEST(ignTest, cmdTopicEcho)
   transport::Node node;
 
   // Requesting a null topic should trigger an error message.
-  cmdTopicEcho(nullptr, 10.00, 0);
+  cmdTopicEcho(nullptr, 10.00, 0, MsgOutputFormat::kDefault);
   EXPECT_EQ(stdErrBuffer.str(), "Invalid topic. Topic must not be empty.\n");
   clearIOStreams(stdOutBuffer, stdErrBuffer);
 
-  cmdTopicEcho(kInvalidTopic.c_str(), 5.00, 0);
+  cmdTopicEcho(kInvalidTopic.c_str(), 5.00, 0, MsgOutputFormat::kDefault);
   EXPECT_EQ(stdErrBuffer.str(), "Topic [/] is not valid.\n");
   clearIOStreams(stdOutBuffer, stdErrBuffer);
 
   restoreIO();
 }
 
+/////////////////////////////////////////////////
+TEST(ignTest, cmdTopicEchoOutputFormats)
+{
+  std::stringstream  stdOutBuffer;
+  std::stringstream  stdErrBuffer;
+  redirectIO(stdOutBuffer, stdErrBuffer);
+
+  transport::Node node;
+  ignition::msgs::Int32 msg;
+  msg.set_data(5);
+
+  clearIOStreams(stdOutBuffer, stdErrBuffer);
+
+  auto getSubscriberOutput = [&](MsgOutputFormat _outputFormat)
+  {
+    cmdTopicEcho(g_topic.c_str(), 3.00, 1, _outputFormat);
+    return stdOutBuffer.str();
+  };
+
+  auto defaultOutput = std::async(std::launch::async, getSubscriberOutput,
+                                  MsgOutputFormat::kDefault);
+
+  cmdTopicPub(g_topic.c_str(), g_intType.c_str(), msg.DebugString().c_str());
+  EXPECT_EQ("data: 5\n\n", defaultOutput.get());
+
+  clearIOStreams(stdOutBuffer, stdErrBuffer);
+
+  auto jsonOutput = std::async(std::launch::async, getSubscriberOutput,
+                               MsgOutputFormat::kJSON);
+
+  msg.set_data(10);
+  cmdTopicPub(g_topic.c_str(), g_intType.c_str(), msg.DebugString().c_str());
+  EXPECT_EQ("{\"data\":10}\n", jsonOutput.get());
+
+  clearIOStreams(stdOutBuffer, stdErrBuffer);
+
+  restoreIO();
+}
+
 /////////////////////////////////////////////////
 /// Main
 int main(int argc, char **argv)

src/cmd/topic_main.cc

@@ -53,6 +53,9 @@ struct TopicOptions
 
   /// \brief Number of messages to echo
   int count{-1};
+
+  /// \brief Message output format
+  MsgOutputFormat msgOutputFormat {MsgOutputFormat::kDefault};
 };
 
 //////////////////////////////////////////////////
@@ -73,7 +76,8 @@ void runTopicCommand(const TopicOptions &_opt)
                   _opt.msgData.c_str());
       break;
     case TopicCommand::kTopicEcho:
-      cmdTopicEcho(_opt.topic.c_str(), _opt.duration, _opt.count);
+      cmdTopicEcho(_opt.topic.c_str(), _opt.duration, _opt.count,
+                   _opt.msgOutputFormat);
       break;
     case TopicCommand::kNone:
     default:
@@ -119,6 +123,10 @@ void addTopicFlags(CLI::App &_app)
       opt->command = TopicCommand::kTopicEcho;
     });
 
+  command->add_flag_callback("--json-output",
+      [opt]() { opt->msgOutputFormat = MsgOutputFormat::kJSON; },
+      "Output messages in JSON format");
+
   command->add_option_function<std::string>("-p,--pub",
       [opt](const std::string &_msgData){
         opt->command = TopicCommand::kTopicPub;