Fix issue with switch screen.

CHANGELOG.md

@@ -12,6 +12,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 
 - Fixed zero division error https://github.com/Textualize/textual/issues/2673
 - Fix `scroll_to_center` when there were nested layers out of view (Compositor full_map not populated fully) https://github.com/Textualize/textual/pull/2684
+- Issues with `switch_screen` not updating the results callback appropriately https://github.com/Textualize/textual/issues/2650
 
 ### Added
 
@@ -35,6 +36,7 @@ and this project adheres to [Semantic Versioning](http://semver.org/).
 - `Tree` and `DirectoryTree` Messages no longer accept a `tree` parameter, using `self.node.tree` instead. https://github.com/Textualize/textual/issues/2529
 - Keybinding <kbd>right</kbd> in `Input` is also used to accept a suggestion if the cursor is at the end of the input https://github.com/Textualize/textual/pull/2604
 - `Input.__init__` now accepts a `suggester` attribute for completion suggestions https://github.com/Textualize/textual/pull/2604
+- Using `switch_screen` to switch to the currently active screen is now a no-op https://github.com/Textualize/textual/pull/2692
 
 ### Removed
 

src/textual/app.py

@@ -1611,15 +1611,19 @@ def switch_screen(self, screen: Screen | str) -> AwaitMount:
             raise TypeError(
                 f"switch_screen requires a Screen instance or str; not {screen!r}"
             )
-        if self.screen is not screen:
-            previous_screen = self._replace_screen(self._screen_stack.pop())
-            previous_screen._pop_result_callback()
-            next_screen, await_mount = self._get_screen(screen)
-            self._screen_stack.append(next_screen)
-            self.screen.post_message(events.ScreenResume())
-            self.log.system(f"{self.screen} is current (SWITCHED)")
-            return await_mount
-        return AwaitMount(self.screen, [])
+
+        next_screen, await_mount = self._get_screen(screen)
+        if screen is self.screen or next_screen is self.screen:
+            self.log.system(f"Screen {screen} is already current.")
+            return AwaitMount(self.screen, [])
+
+        previous_screen = self._replace_screen(self._screen_stack.pop())
+        previous_screen._pop_result_callback()
+        self._screen_stack.append(next_screen)
+        self.screen.post_message(events.ScreenResume())
+        self.screen._push_result_callback(self.screen, None)
+        self.log.system(f"{self.screen} is current (SWITCHED)")
+        return await_mount
 
     def install_screen(self, screen: Screen, name: str) -> None:
         """Install a screen.

tests/test_screens.py

@@ -298,3 +298,55 @@ async def key_p(self) -> None:
         await pilot.press("p")
         with pytest.raises(ScreenStackError):
             app.bottom.dismiss()
+
+
+async def test_switch_screen_no_op():
+    """Regression test for https://github.com/Textualize/textual/issues/2650"""
+
+    class MyScreen(Screen):
+        pass
+
+    class MyApp(App[None]):
+        SCREENS = {"screen": MyScreen()}
+
+        def on_mount(self):
+            self.push_screen("screen")
+
+    app = MyApp()
+    async with app.run_test():
+        screen_id = id(app.screen)
+        app.switch_screen("screen")
+        assert screen_id == id(app.screen)
+        app.switch_screen("screen")
+        assert screen_id == id(app.screen)
+
+
+async def test_switch_screen_updates_results_callback_stack():
+    """Regression test for https://github.com/Textualize/textual/issues/2650"""
+
+    class ScreenA(Screen):
+        pass
+
+    class ScreenB(Screen):
+        pass
+
+    class MyApp(App[None]):
+        SCREENS = {
+            "a": ScreenA(),
+            "b": ScreenB(),
+        }
+
+        def callback(self, _):
+            return 42
+
+        def on_mount(self):
+            self.push_screen("a", self.callback)
+
+    app = MyApp()
+    async with app.run_test():
+        assert len(app.screen._result_callbacks) == 1
+        assert app.screen._result_callbacks[-1].callback(None) == 42
+
+        app.switch_screen("b")
+        assert len(app.screen._result_callbacks) == 1
+        assert app.screen._result_callbacks[-1].callback is None