feat(completion): add pum_matches key to complete_info()

[famiu]

Problem: Currently there is no way of getting the list of completion items that are actually put in the popupmenu. Which means completion providers have no way of knowing if a completion was exhausted.

Solution: Add a pum_matches key to complete_info() which contains the indices of items that are put in the popupmenu.

Ref: vim/vim#10007

[glepnir]

don't get point. When there are no candidate words, that is when match_array is empty, the completechanged event will still be triggered ? idk why there need a new vvar ..complete_info also provide some infomations..

[famiu]

don't get point. When there are no candidate words, that is when match_array is empty, the completechanged event will still be triggered ? idk why there need a new vvar ..complete_info also provide some infomations..

Yes but you still need to know if completion is exhausted or not, and what the completion items are. Currently there is no way of getting that. Also, look at vim/vim#10007 to know why complete_info() is not enough

[glepnir]

It seems that because the items of complete_info are all items, it cannot distinguish the candidate words displayed in the current pum. I implemented similar behavior locally in my completion plugin. Now the order of items will not be disrupted #27955 so you can easily infer the candidate words displayed in the current pum. can't simply add the current index in pum to items, for example the shown_idx field? This should be easier than adding a new vvar.

[zeertzjq]

The name "visible" may also be ambiguous. If there are many matches, there will be a scrollbar and some matches are only shown after scrolling. Should those be considered "visible" or not?

[justinmk]

If there are many matches, there will be a scrollbar and some matches are only shown after scrolling. Should those be considered "visible" or not?

And that should be spelled out in the docs. I thought for sure that the purpose of this PR was to indicate which items are visible on the screen. What, then, is the purpose? (Say it in the docs, not to me)

[echasnovski]

The name "visible" may also be ambiguous. If there are many matches, there will be a scrollbar and some matches are only shown after scrolling. Should those be considered "visible" or not?

True. Maybe "matched" then?

[famiu]

The name "visible" may also be ambiguous. If there are many matches, there will be a scrollbar and some matches are only shown after scrolling. Should those be considered "visible" or not?

True. Maybe "matched" then?

This doesn't work because completion items are called completion matches in several places in the documentation.

I feel like at the end of the day, pum_items probably makes the most amount of sense, or pum_indices or something that makes it clear that we're referring to popupmenu items. Maybe pum_matches?