multiprocessing triggers preLaunchTask and postDebugTask more than once

[omartin2010]

Environment data

• DEBUGPY version: 1.0.0b4
• OS and version: ubuntu18.04
• Python version (& distribution if applicable, e.g. Anaconda): Python 3.6.9
• Using VS Code or Visual Studio:VS Code

Actual behavior

When I launch a simple program that involves multiprocessing, upon firing of another process, the preLaunchTask runs more than one time (once per process as I understand). Same goes for the postDebugTask, which seems to run more than one time.

Expected behavior

The preLaunchTask should run once only, as well as the postDebugTask.

Steps to reproduce:

1. Get this in launch.json :

        {
            "name": "Python: mp.py",
            "type": "python",
            "request": "launch",
            "preLaunchTask": "testStartTask",
            "program": "${workspaceFolder}/testing_code/mp.py",
            "console": "integratedTerminal",
            "debugAdapterPath": "/home/omartin/proj/debugpy/src/debugpy/adapter",
            "postDebugTask": "testStopTask"
        }

2. Get this in tasks.json:

        {
            "label": "testStartTask",
            "type": "shell",
            "isBackground": false,
            "command":[
                "echo helloStart `date`"
            ],
            "options": {
                "shell": {
                    "executable": "/bin/bash",
                    "args": [
                        "-c"
                    ]
                }
            },
            "problemMatcher": [
                "$eslint-compact"
            ]
        },
        {
            "label": "testStopTask",
            "type": "shell",
            "isBackground": false,
            "command":[
                "echo helloStop `date`"
            ],
            "options": {
                "shell": {
                    "executable": "/bin/bash",
                    "args": [
                        "-c"
                    ]
                }
            },
            "problemMatcher": [
                "$eslint-compact"
            ]
        },

3. mp.py looks like this

from multiprocessing import Pool
import traceback


def f(x):
    return x * x


if __name__ == '__main__':
    # start 4 worker processes
    try:
        with Pool(processes=4) as pool:

            # print "[0, 1, 4,..., 81]"
            print(pool.map(f, range(10)))
            print("For the moment, the pool remains available for more work")

    except:
        print(traceback.print_exc())
    # exiting the 'with'-block has stopped the pool
    print("Now the pool is closed and no longer available")

I also needed the fix for connection refused error that I have in my version of debug.py.

It seems, by the output of this, that when my process forks, it runs the preLaunchTask a 2nd time, but for each process that terminates (4 in this example), it runs the postDebugTask.

[omartin2010]

@int19h as discussed, I think you've got all that's needed to repro easily.