[BUG] Progress bar data is not piped when a script using rich is run in a subprocess

Describe the bug

Progress bar updates are not piped via stdout when running any script that uses rich in a subprocess. I specifically noticed this when trying to parse the progress bar of a pip install (pip uses rich for its progress bar), when I noticed that it only pipes the data of the final (finished) bar, and none of the updates.

This stack overflow post I found describes the issue in slightly more detail and provides a minimal repro. They mention using python’s Popen, but the same thing happens in nodejs’s child_process.spawn function.

Here’s an example of what it outputs:

Collecting onnx\r\n
  Downloading onnx-1.11.0-cp39-cp39-win_amd64.whl (11.2 MB)\r\n
---------------------------------------- 11.2/11.2 MB 6.7 MB/s eta 0:00:00\r\n

And what I would expect it to output:

Collecting onnx\r\n
  Downloading onnx-1.11.0-cp39-cp39-win_amd64.whl (11.2 MB)\r\n
     -                                        1.0/11.2 MB 6.7 MB/s eta 0:01:00\r\n
     ----                                     2.2/11.2 MB 6.7 MB/s eta 0:00:50\r\n
     ------------                             6.8/11.2 MB 6.7 MB/s eta 0:00:30\r\n
     ---------------------------              8.2/11.2 MB 6.7 MB/s eta 0:00:20\r\n
     ------------------------------------     10.0/11.2 MB 6.7 MB/s eta 0:00:10\r\n
     ---------------------------------------- 11.2/11.2 MB 6.7 MB/s eta 0:00:00\r\n

Platform Windows

P.S. Please don’t tell me not to run pip install commands this way. I have a specific use case and it will be a waste of time to argue about this. This is a general issue that extends far beyond pip, and I’m sure being able to parse progress bars from scripts is helpful to more people than just me.

[willmcgugan]

Potentially. See https://github.com/pypa/pip/issues/10909 for background

[willmcgugan]

Rich will strip anything dynamic when it detects it is not writing to a console.

If you don’t want this you can force it to behave as a terminal with force_terminal=True. However, since you don’t control that, you should consider using a psuedo-terminal rather than a subprocess.