Display detail of a completion item as info for omnifunc (#136)

* Display `detail` of a completion item as `info` for omnifunc

* Avoid unnecessary string allocations

* Fix "info not always exists in l:completion"

Author: L-TChen

autoload/lsp/omni.vim

@@ -162,12 +162,18 @@ function! lsp#omni#get_vim_completion_item(item) abort
         let l:abbr = a:item['label']
     endif
     let l:menu = lsp#omni#get_kind_text(a:item)
-    let l:completion = { 'word': l:word, 'abbr': l:abbr, 'menu': l:menu, 'icase': 1, 'dup': 1 }
+    let l:completion = { 'word': l:word, 'abbr': l:abbr, 'menu': l:menu, 'info': "", 'icase': 1, 'dup': 1 }
+
+    if has_key(a:item, 'detail') 
+      let l:completion['info'] .= a:item['detail'] . " "
+    endif 
+
     if has_key(a:item, 'documentation')
         if type(a:item['documentation']) == type('')
-            let l:completion['info'] = a:item['documentation']
+            let l:completion['info'] .= a:item['documentation']
         endif
     endif
+
     return l:completion
 endfunction