Add swift completer

[bstaletic]

Here's the status:

• CI: ubuntu works, but macOS refuses to run sourcekit
• I can't get the indexing to work. Does it even work on linux? As a consequence GoToReferences didn't work for me. Tests missing.
• SourceKit doesn't correctly report its CodeAction capabilities, so I had to manually specify that FixIt is supported. Tests missing.
• SourceKit always completes snippets, but for ycmd it removes the snippet markers and basically lies that it's a plain text completion item. This forced me to override ComputeCandidatesInner().
• GoTo on, say, print() returns a location in a binary file with swiftmodule extension. I'm guessing that's the same thing as jdt and locations in class files. _GoToRequest() was overridden to filter out swiftmodule locations.

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This change is 

[puremourning]

It would be pretty cool to hav a working swift completer!

I think if we can't make it work on macOS, there's little value in the completer. Swift adoption outside of iOS/macOS/tvOS development isn't that great, as it misses most of the "standard" library you would expect.

It's a shame that sourcehut indexing is "while u build" rather than clangd-like, and that it refuses to return sensible non-snippet completions.

I guess we need to spend some time on this one. I personally rarely use swift and I suspect that for this to be a long-term success we'll need someone to "sponsor" it, who uses it regularly ? Thoughts ?

Reviewable status: 0 of 40 files reviewed, all discussions resolved

[bstaletic]

I think if we can't make it work on macOS, there's little value in the completer. Swift adoption outside of iOS/macOS/tvOS development isn't that great, as it misses most of the "standard" library you would expect.

I absolutely agree. If I remember correctly, you have tried it locally and it worked. I have no idea what's up with Azure though.

I personally rarely use swift and I suspect that for this to be a long-term success we'll need someone to "sponsor" it, who uses it regularly ? Thoughts ?

Maybe ask on /r/swift or something? I have no clever idea, to be honest.

[bstaletic]

Just an update. I've just tried version 5.3 even though the latest is 5.4.

• macOS CI

Haven't tried.

• Indexing

Haven't tried.

• SourceKit doesn't correctly report its CodeAction capabilities, so I had to manually specify that FixIt is supported. Tests missing.

Still the case.

• SourceKit always completes snippets, but for ycmd it removes the snippet markers and basically lies that it's a plain text completion item. This forced me to override ComputeCandidatesInner().

Yup, still the case.

• GoTo on, say, print() returns a location in a binary file with swiftmodule extension. I'm guessing that's the same thing as jdt and locations in class files. _GoToRequest() was overridden to filter out swiftmodule locations.

This one is fixed in the server.