Swift support?

[konrad1977]

Hi i couldnt find support for swift. It's this something that is planned or easily added?

[skangas]

Hi!

In most cases it should be trivial to add to eglot-server-programs using something like:

(add-to-list 'eglot-server-programs '(foo-mode . ("foo-language-server" "--args")))

If you could tell us the mode and the command to start the language server, it would be trivial to add it. Some language servers are worse than others though, and might need particular support code (e.g. Java). I don't know if Swift is one of them.

[konrad1977]

Yeah, I got it working. But it doesnt complete-at-point. Nor does lsp-sourcekit maybe something is wrong with apples lsp server? According to Apple it has a lot of things supported that doesnt work. Like rename https://github.com/apple/sourcekit-lsp

There is a command to find lsp-sourcekit on mac.
$ xcrun --find sourcekit-lsp
prints the following : /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/sourcekit-lsp

Let me know if I can be of any assistance.

[konrad1977]

Did a comparison with VSCode and SDE (Swift Development) and they seem to work the same. Its probably lsp-sourcekit that doesn't work correctly. I don't get completion of inner variables of structs/classes. Only current file.

Here is a picture comparing VS Code and Emacs and Eglot.

[nemethf]

Its probably lsp-sourcekit that doesn't work correctly.

I don't follow this discussion closely, but there's seems to be a misunderstanding. lsp-sourcekit requires lsp-mode and not Eglot. However, if the problem turns out to be in Eglot, filling out a proper bug report will greatly help the developers of Eglot to work on the issue.

Also, @konrad1977 said he "got it working", but for others to benefit, we need the exact settings of eglot-server-programs.

[konrad1977]

I am new to lsp/eglot and emacs in general. But I thought you could got get full syntax-highlighting and code-completion. But maybe that's not the case?

I meant that the bugs are in https://github.com/apple/sourcekit-lsp and not in lsp-sourcekit (which is now a part of lsp-mode).

This is how I load swift support for eglot. I take no credibility (found it on GitHub)

(setq mk-sourcekit-lsp-options '("--sync"))
  (defun mk-sourcekit-lsp-executable ()
	(setq mk-sourcekit-lsp-executable
          (cond ((executable-find "sourcekit-lsp"))
				((equal system-type 'darwin)
				 (cond ((executable-find "/Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin/sourcekit-lsp"))
					   ((executable-find "/usr/local/bin/sourcekit-lsp"))
                       ((executable-find "/Library/Developer/CommandLineTools/usr/bin/sourcekit-lsp"))))
				((equal system-type 'gnu/linux)
				 (cond ((executable-find "/home/linuxbrew/.linuxbrew/bin/sourcekit-lsp"))))
				(t
				 ("sourcekit-lsp")))))

  (defun mk-sourcekit-lsp-command (interactive)
	(append (list (mk-sourcekit-lsp-executable)) mk-sourcekit-lsp-options))

  (use-package eglot
	:config
	(add-to-list 'eglot-server-programs '((swift-mode) . mk-sourcekit-lsp-command)))

I don't think you need any options ("--sync")

[woolsweater]

There's some unfortunate naming confusion here. sourcekit-lsp is Apple's implementation of an LSP server, based on its SourceKit tool. lsp-sourcekit is an Emacs package that plugs the Apple LSP server into lsp-mode (another Emacs package).

If you are using Eglot, you do not need lsp-sourcekit. You just need to tell Eglot where the sourcekit-lsp binary is on your system. That's what your snippet does.

In some cases you might also want to pass some compiler flags. For example, when doing iOS development you might want to pass the iOS SDK. You can see one possible way to do this in my Emacs config. (Please feel free to use/adapt that code if you wish.)

As for the completion behavior, Apple's LSP server does not recognize Xcode-based projects. In order to get project-wide completion it is pretty much required to have a Package.swift manifest. The swift build command also needs to be run to generate the source code index. It also does not update automatically -- the build needs to be re-run when new interfaces are added. (There are suggestions scattered around the web for alternatives, such as getting a 'compile_commands.json' file for an Xcode project. sourcekit-lsp will use that as a fallback, but I haven't found this or other options to work well at all.) And you are correct that this is on the LSP server side, and not due to anything in the Emacs packages (Eglot/lsp-mode).

[joaotavora]

Nice explanation . Going to try to convert this into a discussion and mark your post the answer.