add app to active message pump (#2071)

* add app to active message pump

* made sender private

* changelog

CHANGELOG.md

@@ -11,10 +11,15 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Dropped "loading-indicator--dot" component style from LoadingIndicator https://github.com/Textualize/textual/pull/2050
 
+### Removed
+
+- Removed `sender` attribute from messages. It's now just private (`_sender`). https://github.com/Textualize/textual/pull/2071
+
 ### Fixed
 
 - Fixed borders not rendering correctly. https://github.com/Textualize/textual/pull/2074
 
+
 ### Changed
 
 - Breaking change: changed default behaviour of `Vertical` (see `VerticalScroll`) https://github.com/Textualize/textual/issues/1957

src/textual/app.py

@@ -53,7 +53,7 @@ from ._ansi_sequences import SYNC_END, SYNC_START
 from ._asyncio import create_task
 from ._callback import invoke
 from ._compose import compose
-from ._context import active_app
+from ._context import active_app, active_message_pump
 from ._event_broker import NoHandler, extract_handler_actions
 from ._path import _make_path_object_relative
 from ._wait import wait_for_idle
@@ -918,6 +918,7 @@ class App(Generic[ReturnType], DOMNode):
             )
 
         # Launch the app in the "background"
+        active_message_pump.set(app)
         app_task = create_task(run_app(app), name=f"run_test {app}")
 
         # Wait until the app has performed all startup routines.
@@ -973,6 +974,7 @@ class App(Generic[ReturnType], DOMNode):
                         raise
 
                 pilot = Pilot(app)
+                active_message_pump.set(self)
                 auto_pilot_task = create_task(
                     run_auto_pilot(auto_pilot, pilot), name=repr(pilot)
                 )

src/textual/driver.py

@@ -42,6 +42,7 @@ class Driver(ABC):
 
     def process_event(self, event: events.Event) -> None:
         """Performs some additional processing of events."""
+        event._set_sender(self._target)
         if isinstance(event, events.MouseDown):
             self._mouse_down_time = event.time
             if event.button:

src/textual/message.py

@@ -64,12 +64,6 @@ class Message:
         if namespace is not None:
             cls.namespace = namespace
 
-    @property
-    def sender(self) -> MessageTarget:
-        """The sender of the message."""
-        assert self._sender is not None
-        return self._sender
-
     @property
     def is_forwarded(self) -> bool:
         return self._forwarded