Add some stubs for completion

autoload/langserver/completion.vim

@@ -0,0 +1,38 @@
+function! langserver#completion#callback(id, data, event) abort
+  let l:parsed_data = langserver#callbacks#data(a:id, a:data, a:event)
+  if l:parsed_data == {}
+    return
+  endif
+
+  " {'isIncomplete': bool, 'items': [CompletionItems]}
+  let l:completion_items = l:parsed_data['items']
+
+endfunction
+
+function! langserver#completion#request(...) abort
+  return langserver#client#send(langserver#util#get_lsp_id(), {
+        \ 'method': 'textDocument/completion',
+        \ 'params': langserver#util#get_text_document_position_params(),
+        \ })
+endfunction
+
+let s:CompletionItemKind = {
+      \ 'Text': 1,
+      \ 'Method': 2,
+      \ 'Function': 3,
+      \ 'Constructor': 4,
+      \ 'Field': 5,
+      \ 'Variable': 6,
+      \ 'Class': 7,
+      \ 'Interface': 8,
+      \ 'Module': 9,
+      \ 'Property': 10,
+      \ 'Unit': 11,
+      \ 'Value': 12,
+      \ 'Enum': 13,
+      \ 'Keyword': 14,
+      \ 'Snippet': 15,
+      \ 'Color': 16,
+      \ 'File': 17,
+      \ 'Reference': 18
+      \ }

rplugin/python3/deoplete/langserver.py

@@ -0,0 +1,24 @@
+from .base import  Base
+
+
+class Source(Base):
+    def __init__(self, nvim):
+        super(Source, self).__init__(nvim)
+
+        self.nvim = nvim
+        self.name = langserver
+        self.mark = '[LSP]'
+
+    def on_event(self, context, filename=''):
+        pass
+
+    def gather_candidates(self, context):
+        user_input = context['input']
+        filetype = context.get('filetype', '')
+        complete_str  context['complete_str']
+
+        return [
+            {
+                'word': user_input + '_hello',
+            }
+        ]