apply markdown for output (#1100)

Author: prabirshrestha

autoload/lsp/ui/vim/output.vim

@@ -2,6 +2,14 @@ let s:use_vim_popup = has('patch-8.1.1517') && g:lsp_preview_float && !has('nvim
 let s:use_nvim_float = exists('*nvim_open_win') && g:lsp_preview_float && has('nvim')
 let s:use_preview = !s:use_vim_popup && !s:use_nvim_float
 
+function! s:import_modules() abort
+    if exists('s:Markdown') | return | endif
+    let s:Markdown = vital#lsp#import('VS.Vim.Syntax.Markdown')
+    let s:MarkupContent = vital#lsp#import('VS.LSP.MarkupContent')
+    let s:Window = vital#lsp#import('VS.Vim.Window')
+    let s:Text = vital#lsp#import('VS.LSP.Text')
+endfunction
+
 let s:winid = v:false
 let s:prevwin = v:false
 let s:preview_data = v:false
@@ -386,6 +394,11 @@ function! lsp#ui#vim#output#preview(server, data, options) abort
       doautocmd <nomodeline> User lsp_float_opened
     endif
 
+    if l:ft ==? 'markdown'
+        call s:import_modules()
+        call s:Window.do(s:winid, {->s:Markdown.apply()})
+    endif
+
     if !g:lsp_preview_keep_focus
         " set the focus to the preview window
         call win_gotoid(s:winid)
@@ -406,7 +419,6 @@ function! lsp#ui#vim#output#append(data, lines, syntax_lines) abort
         return 'markdown'
     elseif type(a:data) ==# type('')
         call extend(a:lines, split(s:escape_string_for_display(a:data), "\n", v:true))
-
         return 'markdown'
     elseif type(a:data) ==# type({}) && has_key(a:data, 'language')
         let l:new_lines = split(s:escape_string_for_display(a:data.value), '\n')
@@ -418,11 +430,15 @@ function! lsp#ui#vim#output#append(data, lines, syntax_lines) abort
         endwhile
 
         call extend(a:lines, l:new_lines)
-
         return 'markdown'
     elseif type(a:data) ==# type({}) && has_key(a:data, 'kind')
-        call extend(a:lines, split(s:escape_string_for_display(a:data.value), '\n', v:true))
-
+        if a:data.kind ==? 'markdown'
+            call s:import_modules()
+            let l:detail = s:MarkupContent.normalize(a:data.value)
+            call extend(a:lines, s:Text.split_by_eol(l:detail))
+        else
+            call extend(a:lines, split(s:escape_string_for_display(a:data.value), '\n', v:true))
+        endif
         return a:data.kind ==? 'plaintext' ? 'text' : a:data.kind
     endif
 endfunction