feat: Update TopicUpdate Transaction (#2479)

Signed-off-by: aceppaluni <aceppaluni@gmail.com>

Author: aceppaluni

src/hiero_sdk_python/consensus/topic_update_transaction.py

@@ -13,7 +13,7 @@
 from hiero_sdk_python.crypto.key import Key
 from hiero_sdk_python.Duration import Duration
 from hiero_sdk_python.executable import _Method
-from hiero_sdk_python.hapi.services import consensus_update_topic_pb2, duration_pb2, timestamp_pb2, transaction_pb2
+from hiero_sdk_python.hapi.services import consensus_update_topic_pb2, duration_pb2, transaction_pb2
 from hiero_sdk_python.hapi.services.custom_fees_pb2 import FeeExemptKeyList, FixedCustomFeeList
 from hiero_sdk_python.hapi.services.schedulable_transaction_body_pb2 import (
     SchedulableTransactionBody,
@@ -33,7 +33,7 @@ def __init__(
         memo: str | None = None,
         admin_key: Key | None = None,
         submit_key: Key | None = None,
-        auto_renew_period: Duration | None = Duration(7890000),
+        auto_renew_period: Duration | None = None,
         auto_renew_account: AccountId | None = None,
         expiration_time: Timestamp | None = None,
         custom_fees: list[CustomFixedFee] | None = None,
@@ -157,7 +157,7 @@ def set_auto_renew_account(self, account_id: AccountId) -> TopicUpdateTransactio
         self.auto_renew_account = account_id
         return self
 
-    def set_expiration_time(self, expiration_time: timestamp_pb2.Timestamp) -> TopicUpdateTransaction:
+    def set_expiration_time(self, expiration_time: Timestamp) -> TopicUpdateTransaction:
         """
         Sets the expiration time for the topic.
 
@@ -243,12 +243,7 @@ def _build_proto_body(self) -> consensus_update_topic_pb2.ConsensusUpdateTopicTr
 
         Returns:
             ConsensusUpdateTopicTransactionBody: The protobuf body for this transaction.
-
-        Raises:
-            ValueError: If required fields are missing.
         """
-        if self.topic_id is None:
-            raise ValueError("Missing required fields: topic_id")
 
         custom_fees = (
             FixedCustomFeeList(fees=[custom_fee._to_topic_fee_proto() for custom_fee in self.custom_fees])
@@ -263,7 +258,7 @@ def _build_proto_body(self) -> consensus_update_topic_pb2.ConsensusUpdateTopicTr
         )
 
         return consensus_update_topic_pb2.ConsensusUpdateTopicTransactionBody(
-            topicID=self.topic_id._to_proto(),
+            topicID=self.topic_id._to_proto() if self.topic_id else None,
             adminKey=key_to_proto(self.admin_key) if self.admin_key else None,
             submitKey=key_to_proto(self.submit_key) if self.submit_key else None,
             autoRenewPeriod=(

tests/unit/topic_update_transaction_test.py

@@ -260,15 +260,16 @@ def test_build_scheduled_body(topic_id):
 
 # This test uses fixture mock_account_ids as parameter
 def test_missing_topic_id_in_update(mock_account_ids):
-    """Test that building fails if no topic ID is provided."""
+    """Test that a missing topic ID is deferred to network validation."""
     _, _, node_account_id, _, _ = mock_account_ids
 
     tx = TopicUpdateTransaction(topic_id=None, memo="No ID")
     tx.operator_account_id = AccountId(0, 0, 2)
     tx.node_account_id = node_account_id
 
-    with pytest.raises(ValueError, match="Missing required fields"):
-        tx.build_transaction_body()
+    transaction_body = tx.build_transaction_body()
+
+    assert not transaction_body.consensusUpdateTopic.HasField("topicID")
 
 
 # This test uses fixtures (mock_account_ids, topic_id, private_key) as parameters
@@ -424,3 +425,19 @@ def test_topic_memo_serialization_distinguishes_unset_and_empty(
     body = tx.build_transaction_body().consensusUpdateTopic
     assert body.HasField("memo")
     assert body.memo.value == "hello"
+
+
+def test_auto_renew_period_omitted_when_unset(
+    mock_account_ids,
+    topic_id,
+):
+    """Unset auto-renew period should not be serialized."""
+    _, _, node_account_id, _, _ = mock_account_ids
+
+    tx = TopicUpdateTransaction(topic_id=topic_id)
+    tx.operator_account_id = AccountId(0, 0, 2)
+    tx.node_account_id = node_account_id
+
+    body = tx.build_transaction_body().consensusUpdateTopic
+
+    assert not body.HasField("autoRenewPeriod")