Autocomplete : Unhandled tab stop types from LSP specification

[tiesselune]

Describe the issue

Hi! First, thanks for the great tech! CodeMirror is exactly what I needed for my project.

But I stumbled upon an issue while combining autocompletion with lsp-client : it seems that the regexp for tab stops here :

      while (m = /[#$]\{(?:(\d+)(?::([^{}]*))?|((?:\\[{}]|[^{}])*))\}/.exec(line)) {

does not handle "simple" tab stops like $1, $0, etc, as defined in the LSP specification. These are heavily used in rust-analyzer, for instance. My workaround is to intercept the messages and convert all $n formatted tab stops into ${}, but it feels a bit hacky and it would probably be best handled in the regexp I linked.

The other issue is that the spec defines $0 as the last tab stop, and it looks like the code would handle it as the first (${0} does that)

I'd like to help, though, but was not sure if this support was not included for a specific reason. If there isn't, I'd gladly submit a PR and give back to the community. Just let me know :)

Browser and platform

No response

Reproduction link

No response

[marijnh]

It looks like there's a whole bunch of other features that snippet from @codemirror/autocomplete doesn't support expected here (${1|one,two,three|} should pop up a choice interface, something with inserting the value of variables, regexp transforms on those variables).

I guess the way forward would be to add these features to @codemirror/autocomplete. For the plain $1 style markers (and $name too, which seems to also be a valid marker), we'll definitely need an opt-in option, I guess a second argument to snippet could control this.

We can then have lsp-client pass this argument and get support for these.

[marijnh]

I've decided I really don't want to implement the whole set of features described for snippets in the spec. That part reads like a sloppy summary of whatever VS Code happens to support, with a bunch of features that feel poorly thought out, and a 'grammar' containing several obvious mistakes.

So, as a minimal workaround, attached patch just crudely substitutes $1 → ${1}