Simplify search code for keyword searches.

We use an array now to build up the list of search operands and
then consolidate the special search handling after the loop (which
means setting the flag, putting two more columns in the query, and
using ' '.join to build the string).

zerver/views/messages.py

@@ -565,28 +565,31 @@ def add_narrow_conditions(user_profile: UserProfile,
     if first_visible_message_id > 0:
         query = query.where(inner_msg_id_col >= first_visible_message_id)
 
-    is_search = False
+    is_search = False  # for now
 
     if narrow is None:
         return (query, is_search)
 
     # Build the query for the narrow
     builder = NarrowBuilder(user_profile, inner_msg_id_col)
-    search_term = {}  # type: Dict[str, Any]
+    search_operands = []
 
+    # As we loop through terms, builder does most of the work to extend
+    # our query, but we need to collect the search operands and handle
+    # them after the loop.
     for term in narrow:
         if term['operator'] == 'search':
-            if not is_search:
-                search_term = term
-                query = query.column(column("subject")).column(column("rendered_content"))
-                is_search = True
-            else:
-                # Join the search operators if there are multiple of them
-                search_term['operand'] += ' ' + term['operand']
+            search_operands.append(term['operand'])
         else:
             query = builder.add_term(query, term)
 
-    if is_search:
+    if search_operands:
+        is_search = True
+        query = query.column(column("subject")).column(column("rendered_content"))
+        search_term = dict(
+            operator='search',
+            operand=' '.join(search_operands)
+        )
         query = builder.add_term(query, search_term)
 
     return (query, is_search)