PR: Add Comms to qtconsole

[impact27]

Add comms to qtconsole.

This is based on:
https://jupyter-notebook.readthedocs.io/en/stable/comms.html
https://jupyter-client.readthedocs.io/en/latest/messaging.html

The code is adapted from:
https://github.com/jupyter/notebook/blob/master/notebook/static/services/kernels/comm.js
https://github.com/ipython/ipykernel/blob/master/ipykernel/comm/manager.py
https://github.com/ipython/ipykernel/blob/master/ipykernel/comm/comm.py

[ccordoba12]

This is really awesome!! Thanks a lot @impact27 for it!

I just have one remark: could you add some tests for this? Just to check that the basic functionality is working as expected.

[impact27]

Could you help me with setting up a kernel? I am trying to do the following:

from qtconsole.qt import QtCore

from qtconsole.manager import QtKernelManager
kernel_manager = QtKernelManager()
kernel_manager.start_kernel()
kernel_client = kernel_manager.client()
kernel_client.start_channels(shell=True, iopub=True)

kernel_client.execute(
        """
        class dummy_comm_handler():
            def comm_open(self, comm, msg):
                self.comm = comm
                self.comm.on_msg(self.comm_message)
        
            def comm_message(self, msg):
                self.comm.send(msg)
                print(msg)
        get_ipython().kernel.comm_manager.register_target('test_api', self.comm_open)
        """
        )

class dummy_comm_handler(QtCore.QObject):
    sig_recieved = QtCore.Signal(dict)

    def comm_message(self, msg):
        msg_dict = msg['content']['data']
        self.sig_recieved.emit(msg_dict)
        print(msg_dict)


comm = kernel_client.comm_manager.new_comm('test_api')
handler = dummy_comm_handler()
comm.on_msg(handler.comm_message)
comm.on_close(handler.comm_message)

comm.send({'foo': 5})

But it looks like the ipykernel is not answering. Is there a way to make blocking calls?

[ccordoba12]

Our tests for the Spyder kernel should help you to get started:

https://github.com/spyder-ide/spyder-kernels/blob/master/spyder_kernels/console/tests/test_console_kernel.py

[impact27]

I have added the tests

[ccordoba12]

@impact27, thanks a lot for taking the time and effort to implement this. It'll make our life in Spyder much more easier from now on.