Fix various bugs when loading many buffers (#1511)

* fix languageId incorrectly set to "ctrlspace"

* remove get_line_count_buf() which incorrectly returned line('$') for hidden buffers

The problem was that current buffer may not be the one requested. Later it
caused vim to throw exception about invalid line number when setting text props,
and that led to initialization failure for some buffers (and lsp_buffer_enabled
autocommand not fired).

* don't register server twice

* skip registering server only if server_info matches

* revert changes to lsp#register_server

---------

Co-authored-by: Krzysztof Sachanowicz <[email protected]>

Author: analizator1

autoload/lsp.vim

@@ -1069,7 +1069,7 @@ endfunction
 function! s:get_text_document(buf, server_name, buffer_info) abort
     let l:server = s:servers[a:server_name]
     let l:server_info = l:server['server_info']
-    let l:language_id = has_key(l:server_info, 'languageId') ?  l:server_info['languageId'](l:server_info) : &filetype
+    let l:language_id = has_key(l:server_info, 'languageId') ?  l:server_info['languageId'](l:server_info) : getbufvar(a:buf, '&filetype')
     return {
         \ 'uri': lsp#utils#get_buffer_uri(a:buf),
         \ 'languageId': l:language_id,

autoload/lsp/ui/vim/folding.vim

@@ -1,6 +1,9 @@
 let s:folding_ranges = {}
 let s:textprop_name = 'vim-lsp-folding-linenr'
 
+" imports
+let s:Buffer = vital#lsp#import('VS.Vim.Buffer')
+
 function! s:find_servers() abort
     return filter(lsp#get_allowed_servers(), 'lsp#capabilities#has_folding_range_provider(v:val)')
 endfunction
@@ -30,7 +33,7 @@ function! s:set_textprops(buf) abort
     " Create text property, if not already defined
     silent! call prop_type_add(s:textprop_name, {'bufnr': a:buf, 'priority': lsp#internal#textprop#priority('folding')})
 
-    let l:line_count = s:get_line_count_buf(a:buf)
+    let l:line_count = s:Buffer.get_line_count(a:buf)
 
     " First, clear all markers from the previous run
     call prop_remove({'type': s:textprop_name, 'bufnr': a:buf}, 1, l:line_count)
@@ -43,14 +46,6 @@ function! s:set_textprops(buf) abort
     endwhile
 endfunction
 
-function! s:get_line_count_buf(buf) abort
-    if !has('patch-8.1.1967')
-        return line('$')
-    endif
-    let l:winids = win_findbuf(a:buf)
-    return empty(l:winids) ? line('$') : line('$', l:winids[0])
-endfunction
-
 function! lsp#ui#vim#folding#send_request(server_name, buf, sync) abort
     if !lsp#capabilities#has_folding_range_provider(a:server_name)
         return