RFR 8057113: (fs) Path should have a method to test the filename extension

[Alan Bateman]

On 16/02/2018 21:34, Roger Riggs wrote:
>
> To keep it simple, the last "." that is not the first character can be 
> the delimiter for the extension.
>
>   "."  ext  ""
>   ".." ext ""
>   ".a.b" ext "b"
>   "......." ext ""
>   ".....a" ext "a"
>   "....a.b" ext "b"
>   "..foo" ext "foo"
>
> It might be useful to check how native unix utilities parse these cases
Yes, a small survey is needed before proposing how some of the corner 
cases should work. In the above, you'll find that Python splitpath will 
split "..foo" into "..foo" and "".  I believe .NET's Path.GetExtension 
is simply the equivalent of lastIndexOf. The need for a survey is 
something that came up when this issue was look into a long time ago.

One other thing is to consider whether getExtension is the right way to 
expose this. I've no doubt it will be followed by a request to add a 
method that returns the file name without the extension so we need to 
see how that will work. At one point we had a prototype of a split 
method that returned the name + extension pair, as 2 element String 
array - I'm not saying that is the best solution of course.

-Alan