File.extname considers the whole path as a filename

[sudo-nice]

puts File.extname("/foo.bar/baz")
Expected output: ""
Actual output: ".bar/baz"

Crystal 0.24.1

[straight-shoota]

It's really disturbing this hasn't been noticed before...

Judging from the documentation it seems like this method is supposed to receive only a filename, not an entire path. So you'd be expected to use it as File.extname(File.basename("/foo.bar/baz")).
But that's not very intuitive and I don't think it makes sense this way.

[Sija]

In Ruby it returns nil. Just FYI.

[straight-shoota]

@Sija That's a different thing, please open a new issue if you want to change that. File.extname always returns empty string if there is no extension.

[sudo-nice]

@Sija In Ruby File.extname("/foo.bar/baz") will return an empty string. But puts will return nil, yes.

[ghost]

So you'd be expected to use it as File.extname(File.basename("/foo.bar/baz")).
But that's not very intuitive and I don't think it makes sense this way.

Agreed - it must be a behaviour bug then.

The output ".bar/baz" can quite logically never be an "extension name". I don't
even know how "/" could ever be part of any extname so it sounds like a bug.