Languageclient-neovim: Tagbar-style outline/browser/navigation pane

[nponeccop]

I can run tagbar plugin side by side with LanguageClient to get the outline, but it's double job as the same files are parsed 2 times independently.

• Does the upstream LSP protocol support this feature? E.g. get the list of top-level definitions in a file.
• Is there a "retargetable" version of tagbar which can use "internal" sources as opposed to starting processes? Just like deoplete is a retargetable completion engine.

[DeltaEvo]

Yes the upstream LSP support this feature with textDocument/documentSymbol, it's already implemented in LamguageClient-neovim

I don't think there is a "retargetable" version of tagbar but we can try to create tags from LSP symbols

[nponeccop]

One of the avantages of tagbar is that "It only creates the tags it needs on-the-fly in-memory without creating any files". So maybe it's easier to patch the tagbar to be retargetable, as it already uses a non-file transport. And it's better to develop such a patch together with the LanguageClient part, so we know that the new mechanism in Tagbar fits LanguageClient's needs

[DeltaEvo]

I will try to look TagBar implementation tomorrow and see what can be the best to implement this feature

[nponeccop]

https://github.com/majutsushi/tagbar/blob/master/autoload/tagbar.vim#2677

Here it uses the system() call to refresh the tags. So if you replace

silent let ctags_output = system(a:ctags_cmd)

with

silent let ctags_output = get_tags_as_string_from_LanguageClient()

it will probably work, although in a very dirty way.

[nponeccop]

The output is then parsed here:

https://github.com/majutsushi/tagbar/blob/2261625e299e202fa2e2bf60ab4248212078310f/autoload/tagbar.vim#L1023-L1034

A significant part of tagbar's source is just to refresh tags using temporary files (for unsaved buffers, not for tags) and short-lived processes. There are too many corner-cases in this old-school approach. But tagbar has a polished UI. So in the long run we probably should split it into "clean gui" part and "dirty ctags exectuables and parsing" part.

Oh, and I found how to use our current poor man's tagbar:

:call LanguageClient_textDocument_documentSymbol()
:lopen

[jalcine]

Real talk @nponeccop, it might be best making a separate plug-in that provides a tagbar-esque interface. I can't remember but there's a utility plugin that makes making interfaces like this straight forward.

[jalcine]

It was this one: https://github.com/xolox/vim-misc#handling-of-special-buffers

[nponeccop]

I don't insist on patching tagbar. We could even add our proper tagbar gui as a feature of LanguageClient.
But then we should teach users to configure nvim so both panes are not displayed at the same time.

[autozimu]

Closing this issue for no real progress.

I'm not going to implement this feature in the foreseeable future as it don't seem fit into scope of this project.

Plus, LanguageClient_textDocument_documentSymbol() has already good enough integration with fzf and denite, and is easily extensible when UI is in-place.