RFR: 8298318: (fs) APIs for handling filename extensions [v2]

[Anthony Vanelverdinghe]

On Mon, 20 Nov 2023 23:30:45 GMT, Brian Burkhalter <bpb at openjdk.org> wrote:

>> Add to `java.nio.file.Path` a method `getExtension` to retrieve the `Path`'s extension, and companion methods `removeExtension` and `addExtension`.
>
> Brian Burkhalter has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains three additional commits since the last revision:
> 
>  - 8298318: Correct type in path.getExtension spec
>  - Merge
>  - 8298318: (fs) APIs for handling filename extensions

My two cents:
* for `foo.`, wouldn't `removeExtension().addExtension(getExtension())` result in `foo`, i.e. the invariant be broken?
* for `.gitconfig`, the current implementation of `getExtension()` returns `""` , but according to Windows conventions, the extension is `gitconfig`
* both PowerShell and Python (just 2 I tried) include the dot in the extension, and it seems natural to me to have an invariant that `base + extension = filename`. I assume this was discussed at length already though, so I'm just curious about the rationale for excluding the dot?
* has the idea of introducing a new class and adding a method to Path (`getFileName()` is already taken, so I'd propose `filename()`) been explored? For example, recently I needed to work with extensions and ended up with something like below.


final class Filename implements CharSequence {

    enum Convention {
        DEFAULT,
        WINDOWS
    }

    String base()
    String base(Convention convention)
    String extension()
    String extension(Convention convention)

    LocalizedBase localizedBase() {}
    LocalizedBase localizedBase(Convention convention) {

    // e.g. Java .properties files or .srt subtitle files
    record LocalizedBase(String root, Locale locale) {}

}

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PR Comment: https://git.openjdk.org/jdk/pull/16226#issuecomment-1821371321