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path.relative(dir, dir) returns empty string #4826
Description
path.relative returns empty string when its from and to arguments are identical.
> path.relative(dir, dir)
''Since '' is not a valid path, this can blow up:
function ls (dir) {
dir = path.relative(process.cwd(), dir);
console.log(dir);
// ...
console.log(fs.readdirSync(dir));
}This function ls works most of the time (nonexistent files and permissions aside), but not if dir points to the working directory:
> ls('.')
Error: ENOENT: no such file or directory, scandir ''
at Error (native)
at Object.fs.readdirSync (fs.js:856:18)
at ls (repl:6:16)I find the fact that path.relative returns a valid path, except in one corner case when the two arguments are identical, rather inconvenient.
However, this is probably intentional since there is a test for this introduced in #2106. But I haven't found any reasoning for this, and the reasoning of #2106 itself is not (directly) applicable here: it's one thing to defensively treat empty strings as '.', and the other to return an empty string instead of a valid path.
Expected bahavior:
> path.relative(dir, dir)
'.'
Activity
silverwind commentedon Jan 24, 2016
I see what you mean, but
'.'means 'current directory' to me, something which does not seem correct for me for arbitrary paths which are equal. It would only be correct whendirequals$PWD.eush77 commentedon Jan 24, 2016
That's not actually correct. Every directory has
'.'and'..', and they can appear anywhere in the path:zeusdeux commentedon Jan 24, 2016
Shouldn't
path.relative(dir, dir)just returndir?silverwind commentedon Jan 24, 2016
No, that would imply there's another sub-directory like
/dir/dirwhendir = '/dir'.Right, I see returning
'.'has some uses, likeprocess.chdir(path.relative(process.cwd(), 'dir')). Still, I'm uncomfortable with breaking documented behaviour.evanlucas commentedon Jan 29, 2016
This is documented at https://nodejs.org/dist/latest-v5.x/docs/api/path.html#path_path_relative_from_to.
I'll go ahead and close. Thanks!