The console outputs more after restarting the debugger

[ChenTanyi]

Environment

VS2017 + ptvsd 3.1.0 / VSCode 1.16.0 + python extension 0.7.0 + ptvsd 3.0.0

python 2.7.13 + windows 10

Behavior

In VSCode: See Issue in python extension.

In VS2017:

The first time I saw this bug was when I did python remote debug with docker in VSCode. I thought it was due to the extension so I open the issue in it. Then I try it in VS2017 and see the bug again. So I think it is due to the ptvsd package.

In the example, I run a simple python program and attach it. Every time I restart the debugger, the debug console would print one more Hello in a iteration. I think the Hello should be printed once a iteration.

ptvsd version and reproduce

As for the ptvsd version, the VS2017 could only run with 3.1.0 and the python extension for VSCode should only run with 3.0.0. I can't even run ptvsd 3.2.0 in python 2.7.13, and I don't known how to test with 3.2.1.

I think it easy to reproduce for source code is clear in the gif. And another source code I run for VSCode with docker is in my repository.

Thanks!

[zooba]

We probably need some way to detect that we've already called enable_output_redirection() and not call it again, but that's not exactly going to be trivial. We can likely handle really simple cases though - it depends how many other frameworks/packages are trying to override the standard streams.