Merge the handling of on_result and async result handling

android/src/toga_android/dialogs.py

@@ -31,10 +31,8 @@ def __init__(
         positive_text,
         negative_text=None,
         icon=None,
-        on_result=None,
     ):
         super().__init__(interface=interface)
-        self.on_result = on_result
 
         self.native = AlertDialog.Builder(interface.window._impl.app.native)
         self.native.setCancelable(False)
@@ -57,54 +55,49 @@ def __init__(
         self.native.show()
 
     def completion_handler(self, return_value: bool) -> None:
-        self.on_result(return_value)
-        self.interface.future.set_result(return_value)
+        self.interface.set_result(return_value)
 
 
 class InfoDialog(TextDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             positive_text="OK",
-            on_result=on_result,
         )
 
 
 class QuestionDialog(TextDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             positive_text="Yes",
             negative_text="No",
-            on_result=on_result,
         )
 
 
 class ConfirmDialog(TextDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             positive_text="OK",
             negative_text="Cancel",
-            on_result=on_result,
         )
 
 
 class ErrorDialog(TextDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             positive_text="OK",
             icon=R.drawable.ic_dialog_alert,
-            on_result=on_result,
         )
 
 
@@ -114,7 +107,6 @@ def __init__(
         interface,
         title,
         message,
-        on_result=None,
         **kwargs,
     ):
         super().__init__(interface=interface)
@@ -129,7 +121,6 @@ def __init__(
         filename,
         initial_directory,
         file_types=None,
-        on_result=None,
     ):
         super().__init__(interface=interface)
         interface.window.factory.not_implemented("Window.save_file_dialog()")
@@ -143,7 +134,6 @@ def __init__(
         initial_directory,
         file_types,
         multiple_select,
-        on_result=None,
     ):
         super().__init__(interface=interface)
         interface.window.factory.not_implemented("Window.open_file_dialog()")
@@ -156,7 +146,6 @@ def __init__(
         title,
         initial_directory,
         multiple_select,
-        on_result=None,
     ):
         super().__init__(interface=interface)
         interface.window.factory.not_implemented("Window.select_folder_dialog()")

android/src/toga_android/widgets/webview.py

@@ -9,26 +9,17 @@
 
 
 class ReceiveString(dynamic_proxy(ValueCallback)):
-    def __init__(self, future, on_result):
+    def __init__(self, result):
         super().__init__()
-        self.future = future
-        self.on_result = on_result
+        self.result = result
 
     def onReceiveValue(self, value):
         # If the evaluation fails, a message is written to Logcat, but the value sent to
         # the callback will be "null", with no way to distinguish it from an actual null
         # return value.
-        result = json.loads(value)
+        res = json.loads(value)
 
-        # Because this method is called directly from the Android event loop, calling
-        # set_result on a timed-out future would crash the whole testbed with an
-        # InvalidStateError.
-        if self.future.cancelled():  # pragma: nocover
-            pass
-        else:
-            self.future.set_result(result)
-            if self.on_result:
-                self.on_result(result)
+        self.result.set_result(res)
 
 
 class WebView(Widget):
@@ -77,9 +68,7 @@ def set_user_agent(self, value):
         )
 
     def evaluate_javascript(self, javascript, on_result=None):
-        result = JavaScriptResult()
+        result = JavaScriptResult(on_result)
 
-        self.native.evaluateJavascript(
-            javascript, ReceiveString(result.future, on_result)
-        )
+        self.native.evaluateJavascript(javascript, ReceiveString(result))
         return result

changes/2264.misc.rst

@@ -0,0 +1 @@
+Synchronous ``on_result`` handling was merged into AsyncResult.

changes/2264.removal.rst

@@ -0,0 +1 @@
+The use of synchronous ``on_result`` callbacks on dialogs and ``Webview.evaluate_javascript()`` calls has been deprecated. These methods should be used in their asynchronous form.

cocoa/src/toga_cocoa/dialogs.py

@@ -31,11 +31,9 @@ def __init__(
         message,
         alert_style,
         completion_handler,
-        on_result=None,
-        **kwargs
+        **kwargs,
     ):
         super().__init__(interface=interface)
-        self.on_result = on_result
 
         self.native = NSAlert.alloc().init()
         self.native.icon = interface.app.icon._impl.native
@@ -54,39 +52,31 @@ def build_dialog(self):
         pass
 
     def completion_handler(self, return_value: int) -> None:
-        self.on_result(None)
-
-        self.interface.future.set_result(None)
+        self.interface.set_result(None)
 
     def bool_completion_handler(self, return_value: int) -> None:
-        result = return_value == NSAlertFirstButtonReturn
-
-        self.on_result(result)
-
-        self.interface.future.set_result(result)
+        self.interface.set_result(return_value == NSAlertFirstButtonReturn)
 
 
 class InfoDialog(NSAlertDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             alert_style=NSAlertStyle.Informational,
             completion_handler=self.completion_handler,
-            on_result=on_result,
         )
 
 
 class QuestionDialog(NSAlertDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             alert_style=NSAlertStyle.Informational,
             completion_handler=self.bool_completion_handler,
-            on_result=on_result,
         )
 
     def build_dialog(self):
@@ -95,14 +85,13 @@ def build_dialog(self):
 
 
 class ConfirmDialog(NSAlertDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             alert_style=NSAlertStyle.Informational,
             completion_handler=self.bool_completion_handler,
-            on_result=on_result,
         )
 
     def build_dialog(self):
@@ -111,19 +100,18 @@ def build_dialog(self):
 
 
 class ErrorDialog(NSAlertDialog):
-    def __init__(self, interface, title, message, on_result=None):
+    def __init__(self, interface, title, message):
         super().__init__(
             interface=interface,
             title=title,
             message=message,
             alert_style=NSAlertStyle.Critical,
             completion_handler=self.completion_handler,
-            on_result=on_result,
         )
 
 
 class StackTraceDialog(NSAlertDialog):
-    def __init__(self, interface, title, message, on_result=None, **kwargs):
+    def __init__(self, interface, title, message, **kwargs):
         if kwargs.get("retry"):
             completion_handler = self.bool_completion_handler
         else:
@@ -135,7 +123,6 @@ def __init__(self, interface, title, message, on_result=None, **kwargs):
             message=message,
             alert_style=NSAlertStyle.Critical,
             completion_handler=completion_handler,
-            on_result=on_result,
             **kwargs,
         )
 
@@ -216,18 +203,15 @@ def single_path_completion_handler(self, return_value: int) -> None:
         else:
             result = None
 
-        self.on_result(result)
-        self.interface.future.set_result(result)
+        self.interface.set_result(result)
 
     def multi_path_completion_handler(self, return_value: int) -> None:
         if return_value == NSModalResponseOK:
             result = [Path(url.path) for url in self.selected_paths()]
         else:
             result = None
 
-        self.on_result(result)
-
-        self.interface.future.set_result(result)
+        self.interface.set_result(result)
 
 
 class SaveFileDialog(FileDialog):
@@ -247,7 +231,6 @@ def __init__(
             initial_directory=initial_directory,
             file_types=None,  # File types aren't offered by Cocoa save panels.
             multiple_select=False,
-            on_result=on_result,
         )
 
     def create_panel(self, multiple_select):
@@ -271,7 +254,6 @@ def __init__(
             initial_directory=initial_directory,
             file_types=file_types,
             multiple_select=multiple_select,
-            on_result=on_result,
         )
 
     def create_panel(self, multiple_select):
@@ -298,7 +280,6 @@ def __init__(
             initial_directory=initial_directory,
             file_types=None,
             multiple_select=multiple_select,
-            on_result=on_result,
         )
 
     def create_panel(self, multiple_select):

cocoa/src/toga_cocoa/widgets/webview.py

@@ -7,19 +7,14 @@
 from .base import Widget
 
 
-def js_completion_handler(future, on_result=None):
+def js_completion_handler(result):
     def _completion_handler(res: objc_id, error: objc_id) -> None:
         if error:
             error = py_from_ns(error)
             exc = RuntimeError(str(error))
-            future.set_exception(exc)
-            if on_result:
-                on_result(None, exception=exc)
+            result.set_exception(exc)
         else:
-            result = py_from_ns(res)
-            future.set_result(result)
-            if on_result:
-                on_result(result)
+            result.set_result(py_from_ns(res))
 
     return _completion_handler
 
@@ -84,13 +79,10 @@ def set_user_agent(self, value):
         self.native.customUserAgent = value
 
     def evaluate_javascript(self, javascript: str, on_result=None) -> str:
-        result = JavaScriptResult()
+        result = JavaScriptResult(on_result=on_result)
         self.native.evaluateJavaScript(
             javascript,
-            completionHandler=js_completion_handler(
-                future=result.future,
-                on_result=on_result,
-            ),
+            completionHandler=js_completion_handler(result),
         )
 
         return result

core/src/toga/handlers.py

@@ -2,6 +2,7 @@
 import inspect
 import sys
 import traceback
+import warnings
 from abc import ABC
 
 
@@ -112,10 +113,38 @@ def _handler(*args, **kwargs):
 
 
 class AsyncResult(ABC):
-    def __init__(self):
+    def __init__(self, on_result=None):
         loop = asyncio.get_event_loop()
         self.future = loop.create_future()
 
+        ######################################################################
+        # 2023-12: Backwards compatibility
+        ######################################################################
+        if on_result:
+            warnings.warn(
+                "Synchronous `on_result` handlers have been deprecated; use `await` on the asynchronous result",
+                DeprecationWarning,
+            )
+
+            self.on_result = on_result
+        else:
+            self.on_result = None
+        ######################################################################
+        # End backwards compatibility.
+        ######################################################################
+
+    def set_result(self, result):
+        if not self.future.cancelled():
+            self.future.set_result(result)
+            if self.on_result:
+                self.on_result(result)
+
+    def set_exception(self, exc):
+        if not self.future.cancelled():
+            self.future.set_exception(exc)
+            if self.on_result:
+                self.on_result(None, exception=exc)
+
     def __repr__(self):
         return f"<Async {self.RESULT_TYPE} result; future={self.future}>"