Support more advanced snippet syntax

[danielrainer]

https://microsoft.github.io/language-server-protocol/specifications/lsp/3.17/specification/#snippet_syntax

Some snippets already work well, but I noticed that when auto-filling the arms of a match, the placeholders don't get parsed properly.

For example, for the following completing the match arms in this code

    let test = Some(42);
    match test {
        
    }

using the Fill match arms action results in this code:

    let test = Some(42);
    match test {
        Some(${1:_}) => ${2:todo!()},
        None => ${3:todo!()},
    }

It would be great if these placeholders were parsed such that the actual placeholder values are inserted (in this example _, todo!(), and todo!()) and navigation between these is possible (<c-j> and <c-k> using the default mappings).

I took a brief look at the code and it seems that the snippets which are currently not working are parsed in commands.ts:parseSnippet. The working snippets (e.g. the ile postfix snipped) don't seem to be parsed in this function, but I have not yet found out how they are handled. Since those work, there presumably is a working implementation somewhere already.

What's the output of :CocInfo

## versions

vim version: NVIM v0.10.2
node version: v23.1.0
coc.nvim version: 0.0.82-28ad86db 2024-12-07 14:40:45 +0800
coc.nvim directory: ~/.local/share/nvim/lazy/coc.nvim
term: xterm-kitty
platform: linux

## Log of coc.nvim

2024-12-11T00:58:31.435 INFO (pid:69983) [extension:coc-git] - Looking for git in: git
2024-12-11T00:58:31.669 INFO (pid:69983) [plugin] - coc.nvim initialized with node: v23.1.0 after 419
2024-12-11T00:58:31.670 INFO (pid:69983) [services] - LanguageClient Rust Analyzer Language Server state change: stopped => starting
2024-12-11T00:58:31.671 INFO (pid:69983) [attach] - receive notification: highlight []
2024-12-11T00:58:31.680 INFO (pid:69983) [language-client-index] - Language server "rust-analyzer" started with 70007
2024-12-11T00:58:31.729 INFO (pid:69983) [services] - LanguageClient Rust Analyzer Language Server state change: starting => running
2024-12-11T00:58:31.759 INFO (pid:69983) [services] - service rust-analyzer started
2024-12-11T00:58:32.676 INFO (pid:69983) [attach] - receive notification: highlight []
2024-12-11T00:58:33.618 INFO (pid:69983) [attach] - Request action: diagnosticList []
2024-12-11T00:58:34.166 INFO (pid:69983) [attach] - receive notification: highlight []
2024-12-11T00:58:34.314 INFO (pid:69983) [attach] - Request action: diagnosticList []
2024-12-11T00:58:35.003 INFO (pid:69983) [attach] - receive notification: codeAction [ 'cursor' ]
2024-12-11T00:58:35.324 INFO (pid:69983) [attach] - receive notification: highlight []
2024-12-11T00:58:39.645 INFO (pid:69983) [attach] - Request action: diagnosticList []
2024-12-11T00:58:40.946 INFO (pid:69983) [attach] - receive notification: highlight []
2024-12-11T00:58:44.680 INFO (pid:69983) [attach] - receive notification: showInfo []

What's the output of :CocCommand rust-analyzer.serverVersion

rust-analyzer 0.3.2212-standalone

What's your coc-rust-analyzer version? You can get it from :CocList extensions

0.77.5 (also tested locally on the latest commit (4283825)

[fannheyward]

This feature is SnippetTextEdit, added in LSP 3.18 https://microsoft.github.io/language-server-protocol/specifications/lsp/3.18/specification/#snippetTextEdit

I've add partly support in coc-rust-analyzer v0.78.0, the snippet can be applied correctly. I'll add the SnippetTextEdit feature in coc.nvim.

[danielrainer]

Great, thanks!