fix: broken auto changing source

Author: haorenW1025

lua/completion/source.lua

@@ -165,14 +165,18 @@ function M.autoCompletion(manager)
   end
   M.prefixLength = #prefix
 
-  -- force reset chain completion and clear completion cache if entering a new word
-  if (#prefix <= length) then
+  -- force reset chain completion
+  if (#prefix < length) then
     complete.clearCache()
     M.chain_complete_index = 1
     M.stop_complete = false
     manager.changeSource = false
   end
 
+  if (#prefix == 0) then
+    complete.clearCache()
+  end
+
   -- stop auto completion when all sources return no complete-items
   if M.stop_complete == true then return end