Python: Preserve messages when replacing chat history from itself

python/semantic_kernel/contents/chat_history.py

@@ -300,12 +300,13 @@ def extend(self, messages: Iterable[ChatMessageContent]) -> None:
     def replace(self, messages: Iterable[ChatMessageContent]) -> None:
         """Replace the chat history with a list of messages.
 
-        This calls clear() and then extend(messages=messages).
+        The iterable is consumed before clearing the history so it can refer to the current messages.
 
         Args:
             messages: The messages to add to the history.
                 Can be a list of ChatMessageContent instances or a ChatHistory itself.
         """
+        messages = list(messages)
         self.clear()
         self.extend(messages=messages)
 

python/tests/unit/contents/test_chat_history.py

@@ -232,6 +232,34 @@ def test_iter(chat_history: ChatHistory):
         assert message.content == messages[i]
 
 
+@pytest.mark.parametrize(
+    "get_messages",
+    [lambda history: history, lambda history: history.messages, lambda history: iter(history)],
+    ids=["history", "messages", "iterator"],
+)
+def test_replace_from_same_history(chat_history: ChatHistory, get_messages):
+    chat_history.add_user_message("Question")
+    chat_history.add_assistant_message("Answer")
+    expected_messages = list(chat_history)
+    messages = chat_history.messages
+
+    chat_history.replace(get_messages(chat_history))
+
+    assert chat_history.messages == expected_messages
+    assert chat_history.messages is messages
+
+
+def test_replace_from_filtered_history(chat_history: ChatHistory):
+    chat_history.add_system_message("Instructions")
+    chat_history.add_user_message("Question")
+    chat_history.add_assistant_message("Answer")
+    expected_messages = chat_history.messages[:2]
+
+    chat_history.replace(message for message in chat_history if message.role != AuthorRole.ASSISTANT)
+
+    assert chat_history.messages == expected_messages
+
+
 def test_eq():
     # Create two instances of ChatHistory
     chat_history1 = ChatHistory()