Cygwin and msys2 bash activator compatibility

[yilei]

Issue

Run the following via msys2:

$ /c/Users/builder/AppData/Local/Programs/Python/Python39/Scripts/virtualenv.exe --no-pip --no-setuptools --no-wheel -p /c/Users/builder/AppData/Local/Programs/Python/Python39/python.exe /tmp/tmp.uw7eZfvJIO
$ source /tmp/tmp.uw7eZfvJIO/Scripts/activate
$ python
python: command not found

The content of /tmp/tmp.uw7eZfvJIO/Scripts/activate contains VIRTUAL_ENV='C:\tools\msys64\tmp\tmp.uw7eZfvJIO', but it's expected to be VIRTUAL_ENV='/c/tools/msys64/tmp/tmp.uw7eZfvJIO', thus it can't locate python.

I believe the legacy version handles this correctly here:

virtualenv/virtualenv.py

Lines 1742 to 1748 in 4c9899f

	home_dir_msys = (drive and "/{}{}" or "{}{}").format(drive[:1], tail)
	# Run-time conditional enables (basic) Cygwin compatibility
	home_dir_sh = """$(if [ "$OSTYPE" "==" "cygwin" ]; then cygpath -u '{}'; else echo '{}'; fi;)""".format(
	home_dir, home_dir_msys
	)
	files["activate"] = ACTIVATE_SH.replace("__VIRTUAL_ENV__", home_dir_sh)

which contains:

VIRTUAL_ENV="$(if [ "$OSTYPE" "==" "cygwin" ]; then cygpath -u 'C:\tools\msys64\tmp\tmp.uw7eZfvJIO'; else echo '/C/tools/msys64/tmp/tmp.uw7eZfvJIO'; fi;)"

Environment

Provide at least:

• OS: Windows 7, using msys2 v20200903.0.0

[danyeaw]

I am also having this issue. I would be glad to submit a PR if someone could help point me in the right direction. It seems like the creator is correctly building the virtualenv, but we need to modify the path only for setting the VIRTUAL_ENV in the activate script.

[gaborbernat]

You probably want to massage around here https://github.com/pypa/virtualenv/blob/master/src/virtualenv/activation/via_template.py#L36-L39