*ArrayWrapper cannot be used to createPublisher

[qiuzhong]

Take the Byte as example, there is a ByteArrayWrapper class in the generated/std_msgs/std_msgs__msg__Byte.js. It stands for an array of the Byte message type. However, it cannot be used to createPublisher. This code

const rclnodejs = require('./rclnodejs/index.js');

rclnodejs.init().then(() => {
  var node = rclnodejs.createNode('byte_publisher');
  var Byte = rclnodejs.require('std_msgs').msg.Byte;
  var ByteArray = Byte.ArrayType;
  var msg = new ByteArray(3);
  msg.setWrappers([1, 2, 3]);
  // console.log(`${msg.data}`);
  console.log(msg.data[0].data); // print 1
  var publisher = node.createPublisher(ByteArray, 'chatter');
  setInterval(() => {
    console.log(`Publishing: ${msg.data}`);
    publisher.publish(msg);
  }, 500);
  rclnodejs.spin(node);
}).catch((err) => {
  console.log(err);
});

will lead a TypeError when calls createPublisher:

1
TypeError: typeClass.type is not a function
    at Function.createPublisher (/home/qiuzhong/Workspace/Work/ros2/tmp/rclnodejs/lib/publisher.js:57:26)
    at Node.createPublisher (/home/qiuzhong/Workspace/Work/ros2/tmp/rclnodejs/lib/node.js:111:31)
    at rclnodejs.init.then (/home/qiuzhong/Workspace/Work/ros2/tmp/publisher.js:106:24)
    at process._tickCallback (internal/process/next_tick.js:109:7)
    at Module.runMain (module.js:606:11)
    at run (bootstrap_node.js:389:7)
    at startup (bootstrap_node.js:149:9)
    at bootstrap_node.js:504:3

[minggangw]

After I was investigating this issue, I found there is a misunderstanding of the usage of Array type. The fact is that you can't simply create an Array of some kind of Message directly, like above. Instead, you have to create a new type of .msg file,

e.g. If you want to use the array of string, please create a new file named Names.msg and write below and save.

string[] names

Then leverage rosidl_generator_c and rosidl_typesupport_introspection_c to generate corresponding c libraries, which will be used by rclnodejs. This is a little complicated, actually you can just put this msg file under the common_interfaces/std_msgs/msg/ of your ros2 source folder, and add a new line "msg/Names.msg" to the CMakeLists.txt, then build the ros again. All you need will be gererated.

Finally, test like:

const rclnodejs = require('./rclnodejs/index.js');

rclnodejs.init().then(() => {
  var node = rclnodejs.createNode('byte_publisher');
  var Names = rclnodejs.require('std_msg').msg.Names; // Here we assume you put the new msg file into the std_msg
  var msg = new Names;
  msg.names = ['Tom', 'Jerry'];
  var publisher = node.createPublisher(Names, 'chatter');
  setInterval(() => {
    publisher.publish(msg);
  }, 500);
  rclnodejs.spin(node);
}).catch((err) => {
  console.log(err);
});

The rule is that you can't use the Array explicitly.

[qiuzhong]

@minggangw , I tried this. The generated/std_msgs/std_msgs__msg__Names.js was generated. However, I got crash when I ran the the code again:

<--- Last few GCs --->

   10994 ms: Mark-sweep 1382.1 (1434.2) -> 1382.1 (1434.2) MB, 1159.2 / 0.0 ms [allocation failure] [GC in old space requested].
   12148 ms: Mark-sweep 1382.1 (1434.2) -> 1382.1 (1417.2) MB, 1153.5 / 0.0 ms [last resort gc].
   13306 ms: Mark-sweep 1382.1 (1417.2) -> 1382.1 (1417.2) MB, 1158.5 / 0.0 ms [last resort gc].


<--- JS stacktrace --->

==== JS stack trace =========================================

Security context: 0x1af3d33cfb39 <JS Object>
    1: setup [/home/qiuzhong/Workspace/Work/rclnodejs/ros2/RobotWebTools/rclnodejs/node_modules/array-index/index.js:~169] [pc=0x171f4bc4e4d5] (this=0x3be6fd9c6c9 <JS Global Object>,index=5424016)
    2: ensureLength [/home/qiuzhong/Workspace/Work/rclnodejs/ros2/RobotWebTools/rclnodejs/node_modules/array-index/index.js:~139] [pc=0x171f4bc5edd4] (this=0x3be6fd9c6c9 <JS Global Object>,self=0xa040...

FATAL ERROR: CALL_AND_RETRY_LAST Allocation failed - JavaScript heap out of memory
 1: node::Abort() [node]
 2: 0x109bf8c [node]
 3: v8::Utils::ReportApiFailure(char const*, char const*) [node]
 4: v8::internal::V8::FatalProcessOutOfMemory(char const*, bool) [node]
 5: v8::internal::Factory::NewFillerObject(int, bool, v8::internal::AllocationSpace) [node]
 6: v8::internal::Runtime_AllocateInTargetSpace(int, v8::internal::Object**, v8::internal::Isolate*) [node]
 7: 0x171f4b9079a7
Aborted (core dumped)

[minggangw]

I am going to re-check this problem, thanks!

[qiuzhong]

To show the message sent, I added a line console.log(msg.names); before calling the publish. However, if I remove this line, then it seems not crash. The subscription node cannot receive any message in both cases.

[qiuzhong]

The subscription can receive Names type message from publisher now. But the crash remains if msg.names is referred before publish method calling.

[qiuzhong]

Verified. #137 fixes the crash.