cp isn't a thing on Windows

[jacobwilliams]

Checklist

• I added a descriptive title
• I searched open reports and couldn't find a duplicate

What happened?

In _copy_with_shell_fallback there is a cp -a system call. This fails on Windows, which doesn't have cp.

Conda Info

na

Conda Config

na

Conda list

na

Additional Context

No response

[travishathaway]

Hi @jacobwilliams,

Thanks raising this concern. Here's the function definition for reference:

conda-build/conda_build/utils.py

Lines 523 to 542 in 506d46f

	def _copy_with_shell_fallback(src, dst):
	is_copied = False
	for func in (shutil.copy2, shutil.copy, shutil.copyfile):
	try:
	func(src, dst)
	is_copied = True
	break
	except (OSError, PermissionError):
	continue
	if not is_copied:
	try:
	subprocess.check_call(
	f"cp -a {src} {dst}",
	shell=True,
	stderr=subprocess.PIPE,
	stdout=subprocess.PIPE,
	)
	except subprocess.CalledProcessError as e:
	if not os.path.isfile(dst):
	raise OSError(f"Failed to copy {src} to {dst}. Error was: {e}")

This function first attempts to copy the file using the several functions from the shutil module. Each one of those function works on Windows. I understand this probably looks a little weird, but I think it's pretty unlikely that we ever actually reach line 533 where this would be a problem for Windows users.

Were you actually seeing this exception while running conda-build? If so, I'd be really interested to learn more context so we can figure out why that's happening.

[jacobwilliams]

It happened to me on Windows last week (with conda 25.5.1). I had some kind of problem further upstream though also (my package was messed up in some way, i can't remember... a missing file or something... i no longer have the traceback). But it did end up in the cp -a code and failed there. When i fixed my package it all worked again. But it is possible to get here, but on a very bad day. :)

[travishathaway]

Okay, thanks for confirming that @jacobwilliams. We'll leave this open then.

Going forward, I think we just need to add proper detection of whether the program is currently running on Windows. If it is, we should not attempt cp -a and instead present the user with the actual error of why the copy failed. This will be more actionable and less confusing.