Prerequisites

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• Make sure you are able to repro it on the latest released version
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• Refer to Differences between Windows PowerShell 5.1 and PowerShell.

Steps to reproduce

pwsh on Mac is showing odd output when used with /usr/bin/expect
I first noticed this while using pwsh with "unbuffer", which is a shell wrapper for expect

I managed to repro with just:
bash>$ expect -c "spawn pwsh -c [command]; expect eof"
where [command] is another compiled program rather than a cmdlet

For instance:
bash>$ expect -c "spawn pwsh -c Write-Output 'PowerShell 7.3.1'; expect eof"

Works fine, and has the following output:

spawn pwsh -c Write-Output 'PowerShell 7.3.1'`
PowerShell 7.3.1

On the other hand,
bash>$ expect -c "spawn pwsh -c pwsh --version; expect eof"

which should have the same output (and does when not run from expect), outputs this:

spawn pwsh -c pwsh --version
^[[31;1R^[[31;9Rbash>$ ;1R;9R

Note that some of the garbage comes out after the prompt
Also note, this is using expect version 5.45. In addition, I rebuilt expect from brew to be sure, and it was still the same.
No other shells have an issue like this with expect.

This started when I had written a simple python script that writes to stdout and stderr on a clock, and was using it to see when a program's stdout would be buffered, and when it would think it was printing to a terminal and come out in real time. (This was how this all started, as long scripts that buffer their stdout but not stderr can have stack traces that come out dozens if not hundreds of lines from the corresponding output, which is annoying)

Here is the program, in python 3.10.7

import os
import sys
import time

i: int = 0

while i < 4:
    sys.stdout.write(f'Stdout mark {i}{os.linesep}')
    sys.stderr.write(f'Stderr mark {i}{os.linesep}')
    time.sleep(1)
    i += 1

when launched from:
pwsh -c python3 clock.py
The output is as expected:

Stdout mark 0
Stderr mark 0
Stdout mark 1
Stderr mark 1
Stdout mark 2
Stderr mark 2
Stdout mark 3
Stderr mark 3

when launched from:
unbuffer pwsh -c python3 clock.py
(unbuffer being a wrapper for expect) the command hangs for a few seconds, then the output is as follows:

^[[32;1R^[[32;9RStdout mark 0
Stderr mark 0
Stdout mark 1
Stderr mark 1
Stdout mark 2
Stderr mark 2
Stdout mark 3
Stderr mark 3
bash>$ ;1R;9R

Once again, note that some of the garbage is printed into the terminal after prompt is written.

Expected behavior

bash>$ expect -c "spawn pwsh -c pwsh --version; expect eof"
spawn pwsh -c pwsh --version
PowerShell 7.3.1

Actual behavior

bash>$ expect -c "spawn pwsh -c pwsh --version; expect eof"
spawn pwsh -c pwsh --version
^[[32;1R^[[32;9Rbash>$ ;1R;9R

Error details

No response

Environment data

Name                           Value
----                           -----
PSVersion                      7.3.1
PSEdition                      Core
GitCommitId                    7.3.1
OS                             Darwin 21.6.0 Darwin Kernel Version 21.6.0: Wed Aug 10 14:28:35 PDT 2022; root:xnu-8020.141.5~2/RELEASE_ARM64_T8101
Platform                       Unix
PSCompatibleVersions           {1.0, 2.0, 3.0, 4.0…}
PSRemotingProtocolVersion      2.3
SerializationVersion           1.1.0.1
WSManStackVersion              3.0

Visuals

No response