Support for regex-based triggers (LuaSnip)

[helins]

Feature Description

I have some LuaSnip snippets triggered by regexes.
E.g. Insert a nice full date when I type something like 20250302.

Those triggers:

• Are never suggested with auto_show
• Do appear when the menu is open manually on an empty cursor
  • Displayed by their pattern (trig) rather than their name
  • Inserting them inserts their trig
    • For context
    • Insertion would not make sense
    • They should be matched against typed keywords

[Saghen]

This won't be supported in the core but you could detect these yourself and call require('blink.cmp').show()

[helins]

I don't think that's it.
Let me clarify my explanation, suppose those scenarios:

• Empty cursor in insert mode
  • Show the menu
  • Can see the regex indeed
  • Accepting it inserts the actual regex
    • Useless and confusing
    • Should definitely not be part of core behavior
• Type something that matches the regex
  • Show the menu
  • Regex not appearing
  • Therefore cannot be accepted via Blink.cmp

[Saghen]

Aha, sorry I read this too quickly and missed that they were being filtered out. Related #1375

[helins]

Alright, after updating to that super fresh PR and playing around, the problem is simple (if my understanding is correct).

1. By default, regex specifics like %d are not considered valid for a keyword, therefore cannot be searched. E.g. my example above with only %d is unsearchable as such.

2. Arguably, searching by raw regex is not user friendly. Users should remember what to input, not how the actual regex for the match looks like. LuaSnip makes a distinction between trig (the pattern, what is being currently displayed in the menu) and name (which can be human-friendly). I would argue that the menu should display names rather than trigs. That is really the only thing I would change.

Any opinions, @soifou (thanks by the way)?

[soifou]

I think it totally makes sense! Could you share your "nice full date" regex snippet if you don't mind? I'd like to toy around with a reasonable set of snippets to make sure it works as expected before making a new PR.

[helins]

A bit tricky since written in Fennel and calling into my private lib, but to give you an idea:

(LS/s {:trig    "(%d%d%d%d)(%d%d)(%d%d)"
       :name    "date_link"
       :doctrig "20240312"
       :desc    "Inserts Markdown link for the given date"
       :regTrig true}
      (LS/f (fn [_args {: captures}]
              ($/zet/link.date (numeric-capture captures
                                                1)
                               (numeric-capture captures
                                                2)
                               (numeric-capture captures
                                                3)))
            {}))

It captures the year + month + day and calls a function for generating a nice Markdown link to a local "daily note".

So to recap the above thinking, the idea is that it would be more intuitive to search for that snippet using its name. This behavior would apply to all snippets with regTrig set to true).

A another problem with the current pattern-based approach is that the completion menu disappears as digits are typed. This makes sense if you know that those patterns are not incremental. But from a UI perspective, it does not feel intuitive that the menu disappears as you type something that is actually valid. Sadly, that cannot be solved without a signifcant headache. Therefore, after sleeping on it, I keep returning to this idea of using name.

[soifou]

Thank you for the detail answer!

Did some tests today and think the name over regex approach work very well. Could you try the latest revision and tell us if it resolves mainly your issue?

[helins]

Thanks for the prompt implementation!
I've just tried it and it is much better IMO.

Maybe one more thing, more controversial. When accepting a selection, instead of inserting trig as a cue, what about prefering doctrig (when available)? Once again for the sake of human readability.

In the example above, (%d%d%d%d)(%d%d)(%d%d) is not much of a reminder. But 20250303 would be.

[soifou]

@helins could you try my fork using the branch feat/luasnip-regex-doctrig with the following option and let me know if it works for you? I'll create a PR if everything looks good.

sources = {
    providers = {
        snippets = {
            --- @type blink.cmp.LuasnipSourceOptions
            opts = {
                prefer_doc_trig = true
            },
        },
    },
},