prevent showing completions for unknown prefixes

src/extension.ts

@@ -117,11 +117,15 @@ function createCompletionItemProvider(
             }
           }
 
+          if (str.indexOf(separator) === -1) {
             return prefixItems(items, str, prefix)
           }
 
           return []
         }
+
+        return []
+      }
     },
     ...triggerCharacters
   )