Better support for lsp-sourcekit placeholders?

[dabrahams]

(c.f. emacs-lsp/lsp-sourcekit#31)

When I use completion with sourcekit-lsp I often get things of the form ${1:SomeType} in my emacs buffer where Xcode would show a placeholder to be filled in. It would be awesome if that worked better. I imagine supporting this might need some cooperation with lsp-sourcekit. If you look at rust-mode for emacs with LSP, it inserts gray text, that isn't in the file, showing types of things (and other information) everywhere in the buffer. I find that somewhat annoying but it would be perfect for placeholders.

[taku0]

When I use completion with sourcekit-lsp I often get things of the form ${1:SomeType} in my emacs buffer where Xcode would show a placeholder to be filled in. It would be awesome if that worked better. I imagine supporting this might need some cooperation with lsp-sourcekit.

Could you provide us more info? Something like screenshots of Xcode and current swift-mode would help.

If you look at rust-mode for emacs with LSP, it inserts gray text, that isn't in the file, showing types of things (and other information) everywhere in the buffer.

Are you talking about this? https://emacs-lsp.github.io/lsp-mode/page/lsp-rust-analyzer/#inlay-hints

[dabrahams]

Are you talking about this? https://emacs-lsp.github.io/lsp-mode/page/lsp-rust-analyzer/#inlay-hints

Yep, that's it exactly.

Xcode as I'm choosing a completion:

After hitting return (Because it looks a little confusing, I'll explain that I am inserting this precondition call just before another one):

After TAB:

When I type in any field it becomes inactive. When there are any fields active in the buffer TAB will go to one of them and cycle between them.

Emacs LSP choosing a completion:

After hitting return:

[taku0]

Implementation plan:

• When propertizing the buffer, recognize placeholders and add overlays.
• Set keymap property of the overlays for <tab> and <backtab>.
• Set modification-hooks, insert-in-front-hooks, and insert-behind-hooks properties to delete the placeholder before editing.