Feedback requested: what would be the impact of deleting `System.PosixCompat.User` from `unix-compat`?

[mitchellwrosen]

Hi there,

I've recently taken over maintainership of unix-compat, and I intend to push out a unix-2.8-compatible release as soon as I can. One remaining issue is what to make of the System.PosixCompat.User module, as the UserEntry type has changed.

Here is the first PR that attempts to graft over the differences: https://github.com/jacobstanley/unix-compat/pull/60/files

And here is my preferred solution, to delete the System.PosixCompat.User module entirely, based on the observation that System.PosixCompat.User doesn't seem useful at all, as all functions either return dummy data or throw exceptions: jacobstanley/unix-compat#62

However, I see that stack and yi-core actually use this module. For example:

stack/src/Stack/Config.hs

Lines 888 to 899 in 835318b

	-- | Check whether the current user (determined with 'getEffectiveUserId') is
	-- the owner for the given path.
	--
	-- Will always pure 'True' on Windows.
	isOwnedByUser :: MonadIO m => Path Abs t -> m Bool
	isOwnedByUser path = liftIO $
	if osIsWindows
	then pure True
	else do
	fileStatus <- getFileStatus (toFilePath path)
	user <- getEffectiveUserID
	pure (user == fileOwner fileStatus)

This code looks dubious to me: it claims to always return True on Windows, yet I believe it instead always throws an exception on Windows, which may be getting swallowed somewhere else.

But there are other uses, too, in Stack/Docker.hs. So, could you please consider the effect of deleting System.PosixCompat.User on the stack codebase, and let me know if that is a reasonable option, or if you'd rather see a different approach to unix-2.8 support?

Thanks.

[mpilgrem]

@mitchellwrosen, thanks for asking. From Stack's perspective, I think it is a reasonable option to delete System.PosixCompat.User.

osIsWindows is True on Windows, so I would not expect Stack.Config.isOwnedByUser to throw an exception. Stack's Docker support throws unsupported exceptions on Windows - #2421.

[mpilgrem]

Stack no longer imports System.PosixCompat.User.

[mitchellwrosen]

That's great, thank you!

[hamishmack]

I think it might be a good idea to add an upper bound unix-compat <0.7 to https://hackage.haskell.org/package/stack-2.9.3 and https://hackage.haskell.org/package/stack-2.9.1.