avoid exposing asyncio.Future directly to api consumers

src/textual/app.py

@@ -120,6 +120,7 @@
     ScreenResultCallbackType,
     ScreenResultType,
     SystemModalScreen,
+    AwaitScreen,
 )
 from textual.signal import Signal
 from textual.theme import BUILTIN_THEMES, Theme, ThemeProvider
@@ -2650,14 +2651,14 @@ def push_screen(
             screen: Screen[ScreenResultType] | str,
             callback: ScreenResultCallbackType[ScreenResultType] | None = None,
             wait_for_dismiss: Literal[True] = True,
-        ) -> asyncio.Future[ScreenResultType]: ...
+        ) -> AwaitScreen[ScreenResultType]: ...
 
     def push_screen(
         self,
         screen: Screen[ScreenResultType] | str,
         callback: ScreenResultCallbackType[ScreenResultType] | None = None,
         wait_for_dismiss: bool = False,
-    ) -> AwaitMount | asyncio.Future[ScreenResultType]:
+    ) -> AwaitMount | AwaitScreen[ScreenResultType]:
         """Push a new [screen](/guide/screens) on the screen stack, making it the current screen.
 
         Args:
@@ -2670,22 +2671,14 @@ def push_screen(
             NoActiveWorker: If using `wait_for_dismiss` outside of a worker.
 
         Returns:
-            An optional awaitable that awaits the mounting of the screen and its children, or an asyncio Future
+            An optional awaitable that awaits the mounting of the screen and its children, or an awaitable
                 to await the result of the screen.
         """
         if not isinstance(screen, (Screen, str)):
             raise TypeError(
                 f"push_screen requires a Screen instance or str; not {screen!r}"
             )
 
-        try:
-            loop = asyncio.get_running_loop()
-        except RuntimeError:
-            # Mainly for testing, when push_screen isn't called in an async context
-            future: asyncio.Future[ScreenResultType] = asyncio.Future()
-        else:
-            future = loop.create_future()
-
         if self._screen_stack:
             self.screen.post_message(events.ScreenSuspend())
             self.screen.refresh()
@@ -2695,6 +2688,7 @@ def push_screen(
         except LookupError:
             message_pump = self.app
 
+        future: AwaitScreen[ScreenResultType] = AwaitScreen()
         next_screen._push_result_callback(message_pump, callback, future)
         self._load_screen_css(next_screen)
         self._screen_stack.append(next_screen)

src/textual/screen.py

@@ -8,6 +8,7 @@
 
 from __future__ import annotations
 
+import enum
 import asyncio
 from functools import partial
 from operator import attrgetter
@@ -23,6 +24,8 @@
     Optional,
     TypeVar,
     Union,
+    Literal,
+    Generator,
 )
 
 import rich.repr
@@ -82,6 +85,27 @@
 ]
 """Type of a screen result callback function."""
 
+class _Unset(enum.Enum):
+    UNSET = enum.auto()
+
+class AwaitScreen(Generic[ScreenResultType]):
+    def __init__(self) -> None:
+        self._event = asyncio.Event()
+        self._result: ScreenResultType | Literal[_Unset.UNSET] = _Unset.UNSET
+
+    async def wait(self) -> ScreenResultType:
+        await self._event.wait()
+        assert self._result is not _Unset.UNSET
+        return self._result
+
+    def __await__(self) -> Generator[Any, Any, ScreenResultType]:
+        return self.wait().__await__()
+
+    def set_result(self, result):
+        assert self._result is _Unset.UNSET
+        self._result = result
+        self._event.set()
+
 
 @rich.repr.auto
 class ResultCallback(Generic[ScreenResultType]):
@@ -91,7 +115,7 @@ def __init__(
         self,
         requester: MessagePump,
         callback: ScreenResultCallbackType[ScreenResultType] | None,
-        future: asyncio.Future[ScreenResultType] | None = None,
+        future: AwaitScreen[ScreenResultType] | None = None,
     ) -> None:
         """Initialise the result callback object.
 
@@ -1161,7 +1185,7 @@ def _push_result_callback(
         self,
         requester: MessagePump,
         callback: ScreenResultCallbackType[ScreenResultType] | None,
-        future: asyncio.Future[ScreenResultType | None] | None = None,
+        future: AwaitScreen[ScreenResultType] | None = None,
     ) -> None:
         """Add a result callback to the screen.