feat: reduce overhead to answer questions (#1250)

src/zeroconf/_handlers/query_handler.py

@@ -21,7 +21,7 @@
 """
 
 
-from typing import TYPE_CHECKING, List, Set, cast
+from typing import TYPE_CHECKING, List, Optional, Set, cast
 
 from .._cache import DNSCache, _UniqueRecordsType
 from .._dns import DNSAddress, DNSPointer, DNSQuestion, DNSRecord, DNSRRSet
@@ -109,19 +109,20 @@ def add_mcast_question_response(self, answers: _AnswerWithAdditionalsType) -> No
             else:
                 self._mcast_aggregate.add(answer)
 
-    def _generate_answers_with_additionals(self, rrset: Set[DNSRecord]) -> _AnswerWithAdditionalsType:
-        """Create answers with additionals from an rrset."""
-        return {record: self._additionals[record] for record in rrset}
-
     def answers(
         self,
     ) -> QuestionAnswers:
         """Return answer sets that will be queued."""
         return QuestionAnswers(
-            self._generate_answers_with_additionals(self._ucast),
-            self._generate_answers_with_additionals(self._mcast_now),
-            self._generate_answers_with_additionals(self._mcast_aggregate),
-            self._generate_answers_with_additionals(self._mcast_aggregate_last_second),
+            *(
+                {record: self._additionals[record] for record in rrset}
+                for rrset in (
+                    self._ucast,
+                    self._mcast_now,
+                    self._mcast_aggregate,
+                    self._mcast_aggregate_last_second,
+                )
+            )
         )
 
     def _has_mcast_within_one_quarter_ttl(self, record: DNSRecord) -> bool:
@@ -224,17 +225,16 @@ def _answer_question(
         self,
         question: DNSQuestion,
         known_answers: DNSRRSet,
-        now: float,
     ) -> _AnswerWithAdditionalsType:
+        """Answer a question."""
         answer_set: _AnswerWithAdditionalsType = {}
         question_lower_name = question.name.lower()
+        type_ = question.type
 
-        if question.type == _TYPE_PTR and question_lower_name == _SERVICE_TYPE_ENUMERATION_NAME:
+        if type_ == _TYPE_PTR and question_lower_name == _SERVICE_TYPE_ENUMERATION_NAME:
             self._add_service_type_enumeration_query_answers(answer_set, known_answers)
             return answer_set
 
-        type_ = question.type
-
         if type_ in (_TYPE_PTR, _TYPE_ANY):
             self._add_pointer_answers(question_lower_name, answer_set, known_answers)
 
@@ -267,12 +267,15 @@ def async_response(  # pylint: disable=unused-argument
         """
         known_answers = DNSRRSet([msg.answers for msg in msgs if not msg.is_probe])
         query_res = _QueryResponse(self.cache, msgs)
+        known_answers_set: Optional[Set[DNSRecord]] = None
 
         for msg in msgs:
             for question in msg.questions:
                 if not question.unicast:
-                    self.question_history.add_question_at_time(question, msg.now, set(known_answers.lookup))
-                answer_set = self._answer_question(question, known_answers, msg.now)
+                    if not known_answers_set:  # pragma: no branch
+                        known_answers_set = set(known_answers.lookup)
+                    self.question_history.add_question_at_time(question, msg.now, known_answers_set)
+                answer_set = self._answer_question(question, known_answers)
                 if not ucast_source and question.unicast:
                     query_res.add_qu_question_response(answer_set)
                     continue