path.posix.relative returns different results for *nix and Windows versions of node

[usergenic]

• Version: 8.1.1
• Platform: Windows Server
• Subsystem: path.js

This code returns different values depending on whether run on *nix or windows:

path.posix.relative('a/b/c', '../../x');
'../../../..../x' // on windows
'../../../../../x' // on *nix

[vsemozhetbyt]

On Windows, Node.js versions differ:

  // Node.js 4.8.3 (v8 4.5.103.47) x64

../../../.././x

  // Node.js 6.11.0 (v8 5.1.281.102) x64

../../../..../x

  // Node.js 8.1.1 (v8 5.8.283.41) x64

../../../..../x

[DuanPengfei]

I will try to fix it.

[DuanPengfei]

After reading the code found path.posix.relative call posix.resolve first convert path into an absolute path, but posix.resolve's all the parameters have not yet generated an absolute path then it will add the current path to generate the absolute path. Because of current path is platform-related, I think the direct use of path.posix.relative on Windows is not very suitable. And in the debugging of this problem I found the doc of path.relative is not strict, so I also have a PR doc: make path.relative stricter. So I have confusion about this issue, @gibfahn @XadillaX have some advices?

[refack]

The first solution that comes to mind is adding a check (re #13714): if explicitly running the posix variant of path.posix.relative on a Windows platform, throw a TypeError.
More correct (check resolve): if explicitly running the posix variant of path.posix.resolve on a Windows platform, throw a TypeError

[XadillaX]

@DuanPengfei you may create a new PR to check and throw error in posix.resolve.

[DuanPengfei]

👌🏻I will create a new PR.

[addaleax]

@refack Throwing an error instead of fixing the bug seems like a really bad idea; I think there is no reason inherent to the API why path.posix.relative('a/b/c', '../../x') wouldn’t be able to return a correct result on Windows.

[tniessen]

I am a little surprised as well, I didn't follow the conversation, but I wonder why we do not even consider fixing the bug instead of just saying "you cannot use this function on Windows". Did I miss something? Is this really too difficult to implement? How is posix.resolve platform-dependent except for process.cwd()?

[XadillaX]

@addaleax @tniessen relative uses cwd to build the missing part, eg.

path.relative("../../../../x", "y")

[addaleax]

@XadillaX I understand that; but that should work just fine on Windows, no? Also, there’s not always a missing part, for example if you reverse the parameters in your code snippet.

[XadillaX]

if the correct result may be implemented fine, I think to implement is better too.

[DuanPengfei]

If use different systems pwd can produce correct result, of course, that is better, I will try it again later. Create PR because I think use C:\Users\someone as *nix root directory is not reasonable.

[tniessen]

because I think use C:\Users\someone as *nix root directory is not reasonable

Even if it is not, that is not a reason to prevent Windows applications from dealing with posix paths and vice versa. For example, you might want to talk to a posix FTP server from a Windows machine (in which case paths shouldn't be resolved against cwd anyways), so you would need the posix path API.

[DuanPengfei]

So is that means path.posix.resolve can work well in some cases. When it rely on cwd will generate incorrect path or throw error. This is also an acceptable way of compromise I think.

[refack]

I'm not sure which thread is better to comment in, this or #13738 🤔
I suggested there to throw only if resolving requires using process.cwd() since that is a bug.
A solution for this issue could be implemented in parallel.

P.S. The in progress label is used to indicate to other contributors that someone is working on this issue, RE: #13565

[refack]

a posix FTP server from a Windows machine

In that case I would recommend using URL. But there are obviously cases where it's useful to do cross-platform path manipulation, but IMHO we should limit the nonsense outputs, like when process.pwd() is necessary.
(reposting):

> path.posix.resolve('./gaga/')
'C:\\bin\\dev\\node/gaga'  // bug
> path.posix.resolve('/gaga/')
'/gaga'   // Ok

[Trott]

I know this issue is quite old, but if anyone wants to test out #37747 to see if it fixes the issue for them, that would be great.