bugfix: boxes: Set propagate_mode to change_one if topic unchanged.

The intent of the edit/update message API has recently been clarified
that if the topic is unchanged (even if sent) that the propagate_mode
should be set to change_one. This was previously not enforced by the
server but was changed to do so in
zulip/zulip@e231a03

Since our propagate_mode defaults to change_later via the UI element,
the above change to the server leads to errors upon attempting
content-only edits.

To resolve this, the original topic is added to the new tuple form of
msg_edit_state, allowing detection of whether the topic has changed and
setting of propagate_mode as appropriate.

The decision to use change_one is dependent upon the trimmed new topic
since otherwise the edit can confusingly fail since trimming is checked
on the server end and results in the same propagate error message.

Tests updated.

Author: neiljp

tests/ui/test_ui_tools.py

@@ -2306,6 +2306,7 @@ def test_keypress_EDIT_MESSAGE(
 
         if expect_editing_to_succeed:
             assert write_box.msg_edit_state.message_id == varied_message["id"]
+            assert write_box.msg_edit_state.old_topic == varied_message["subject"]
             write_box.msg_write_box.set_edit_text.assert_called_once_with(
                 "Edit this message"
             )

tests/ui_tools/test_boxes.py

@@ -846,7 +846,7 @@ def test__process_typeaheads(
     )
     @pytest.mark.parametrize(
         "msg_edit_state",
-        [_MessageEditState(message_id=10), None],
+        [_MessageEditState(message_id=10, old_topic="old topic"), None],
         ids=["update_message", "send_message"],
     )
     @pytest.mark.parametrize("key", keys_for_command("SEND_MESSAGE"))
@@ -1065,7 +1065,9 @@ def test_keypress_CYCLE_COMPOSE_FOCUS(
             if message_being_edited:
                 mocker.patch(BOXES + ".EditModeButton")
                 write_box.stream_box_edit_view(stream_id)
-                write_box.msg_edit_state = _MessageEditState(message_id=10)
+                write_box.msg_edit_state = _MessageEditState(
+                    message_id=10, old_topic="some old topic"
+                )
             else:
                 write_box.stream_box_view(stream_id)
         else:

zulipterminal/ui_tools/boxes.py

@@ -55,6 +55,7 @@
 
 class _MessageEditState(NamedTuple):
     message_id: int
+    old_topic: str
 
 
 class WriteBox(urwid.Pile):
@@ -543,9 +544,16 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
                     topic = self.title_write_box.edit_text
 
                 if self.msg_edit_state is not None:
+                    trimmed_topic = topic.strip()
+                    # Trimmed topic must be compared since that is server check
+                    if trimmed_topic == self.msg_edit_state.old_topic:
+                        propagate_mode = "change_one"  # No change in topic
+                    else:
+                        propagate_mode = self.edit_mode_button.mode
+
                     args = dict(
                         message_id=self.msg_edit_state.message_id,
-                        topic=topic,
+                        topic=topic,  # NOTE: Send untrimmed topic always for now
                         propagate_mode=self.edit_mode_button.mode,
                     )
                     if self.msg_body_edit_enabled:
@@ -1616,7 +1624,9 @@ def keypress(self, size: urwid_Size, key: str) -> Optional[str]:
             msg_id = self.message["id"]
             msg = self.model.client.get_raw_message(msg_id)["raw_content"]
             write_box = self.model.controller.view.write_box
-            write_box.msg_edit_state = _MessageEditState(message_id=msg_id)
+            write_box.msg_edit_state = _MessageEditState(
+                message_id=msg_id, old_topic=self.message["subject"]
+            )
             write_box.msg_write_box.set_edit_text(msg)
             write_box.msg_write_box.set_edit_pos(len(msg))
             write_box.msg_body_edit_enabled = msg_body_edit_enabled