Unexpected path.join behaviour with windows drives

[Gershy]

Version

14.0.0

Platform

Microsoft Windows NT 10.0.19044.0 x64

Subsystem

No response

What steps will reproduce the bug?

I typically expect path.join(path.join(...paths1), ...paths2) === path.join(...paths1, ...paths2);

This is defied with:

let paths1 = [ 'C:' ];
let paths2 = [ 'abc' ];

Essentially because path.join('C:', 'abc') === 'C:\\abc';, I expect that path.join(path.join('C:'), 'abc') === 'C:\\abc';.

I also expect that if path.isAbsolute(myPath) is false, so too will path.isAbsolute(path.join(myPath, anotherPath)) be false. This can be summarized by saying "if a path is relative, a child path of that path is also relative", and seems like a very reasonable expectation - but it's defied when:

console.log( path.isAbsolute('C:') ); // false
console.log( path.isAbsolute(path.join('C:', 'abc')) ); // true

I also expect path.join(...cmps).split(path.sep) to give me a clone of cmps in most cases (specifically when cmps doesn't contain any .. or . components). This is defied when:

let cmps = [ 'C:' ];
console.log( path.join(...cmps).split(path.sep) ); // I expect [ 'C:' ], but get [ 'C:.' ] (note the "." character)

How often does it reproduce? Is there a required condition?

No context needed

What is the expected behavior?

assert(path.join(path.join('C:'), 'abc') === 'C:\\abc');
assert(path.isAbsolute('C:') === true);

let cmps = path.join('C:').split(path.sep);
assert(cmps.length === 1);
assert(cmps[0] === 'C:');

What do you see instead?

path.join(path.join('C:'), 'abc') === 'C:abc';
path.isAbsolute('C:') === false;
path.join('C:').split(path.sep)[0] === 'C:.';

Additional information

No response

[mscdex]

This is not a bug. When you reference a drive only by its letter followed by a colon, you're referencing the current working directory on that drive, since Windows tracks the last directory you were in on each drive. So a path like 'C:abc' is completely valid and points to an entry called abc in the current working directory on drive C, which may not necessarily be the root path on that drive.

[Gershy]

So a path like 'C:abc' is completely valid...

I'm not sure this accounts for the discrepancy between path.join(path.join('C:'), 'abc'), and path.join('C:', 'abc')...

[bnoordhuis]

path.join('c:') == 'c:.' - note the dot. Joining c: vs. c:. with abc results in different paths. Seems like expected and desired behavior to me.