LSP auto-completion of YAML frontmatter tags

[mickael-menu]

Hello!
Is it planned to add auto-complete on tags in the YAML frontmatter?
It works well when added with # but I use them only in the frontmatter.
Originally posted by @tissieres in #22 (comment)

[mickael-menu]

LSP auto-completion needs a trigger character, which is easy with #hashtags and :colon:tags:, but not with the YAML frontmatter since there's no character distinguishing tags.

A possible workaround would be to use # for the trigger character, and if we detect that we are inside a YAML frontmatter, request the editor to remove it after insertion. Not super straightforward but feasible, I think this would be useful to have in zk.

[kabouzeid]

This is not completely true. Completion is also automatically triggered when typing an identifier, and it can of course always be manually triggered by the user. See (https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#completionOptions) and (https://microsoft.github.io/language-server-protocol/specifications/specification-3-17/#completionTriggerKind).

I've just checked that Neovim will in fact send a complete request when starting to type a tag name (identifier) in the frontmatter. VSCode does the same. This is from the logs:

[DEBUG][2022-01-05 20:32:24] .../vim/lsp/rpc.lua:347	"rpc.send"	{  id = 36,  jsonrpc = "2.0",  method = "textDocument/completion",  params = {    context = {      triggerKind = 1    },    position = {      character = 7,      line = 2    },    textDocument = {      uri = "file:///home/karim/Documents/Zettelkasten/index.md"    }  }}

Notice that context.triggerKind is set to 1 in this case.

[mickael-menu]

Ha that's interesting, do you know if there's a way to request a specific kind of completion item from the client?

[kabouzeid]

I'm not sure I understand what you mean. The client can (and usually does) filter and sort the completion results locally according to user prefs. But how would that help here?

[mickael-menu]

No I mean how do you know whether to complete tags or links (not a great example, but more completion items might be added later on) from the LSP server when receiving this?

Right now, I'm using the value of the triggerCharacter for this.

Or maybe the server is supposed to check the location of the caret to infer the kind of item to complete?

[kabouzeid]

Or maybe the server is supposed to check the location of the caret to infer the kind of item to complete?

Yes :)

[mickael-menu]

I think it would be pretty trivial to support for:

tags: [a, b]

But YAML bullet lists would require more work:

tags:
  - a
  - b

[kabouzeid]

Kind of hacky, but relatively easy and might work very well:
On the server side, we could insert some random string at the completion position, then parse the yaml and see if the inserted random string would be parsed as a tag.

[mickael-menu]

Yeah that should work fine.

[mickael-menu]

Could you check this out #146? I implemented your idea @kabouzeid, it works well but requires the YAML frontmatter to be valid, so if you have a hanging [ or ", it won't auto-complete.

[mickael-menu]

cc @tissieres

[tissieres]

Hi @mickael-menu
Just tested it and it works perfectly for me. BTW, I'm using a template with a valid frontmatter at the beginning:

tags: []

Thanks very much!