Merge pull request #2596 from PistachioCannoli/fix-2325-textinput-val…

…idation

android/src/toga_android/widgets/textinput.py

@@ -111,8 +111,7 @@ def is_valid(self):
         return self.native.getError() is None
 
     def _on_change(self):
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def _on_confirm(self):
         self.interface.on_confirm()

changes/2325.bugfix.rst

@@ -0,0 +1 @@
+Invocation order of TextInput on_change and validation is now correct.

cocoa/src/toga_cocoa/widgets/textinput.py

@@ -213,8 +213,7 @@ def get_value(self):
 
     def set_value(self, value):
         self.native.stringValue = value
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def rehint(self):
         # Height of a text input is known and fixed.

core/src/toga/widgets/textinput.py

@@ -181,6 +181,11 @@ def _validate(self):
         else:
             self._impl.clear_error()
 
+    def _value_changed(self):
+        """Validate the current value of the widget and invoke the on_change handler."""
+        self._validate()
+        self.on_change()
+
     @property
     def on_confirm(self) -> callable:
         """The handler to invoke when the user accepts the value of the widget,

core/tests/widgets/test_textinput.py

@@ -3,6 +3,7 @@
 import pytest
 
 import toga
+from toga.validators import Number
 from toga_dummy.utils import (
     EventLog,
     assert_action_not_performed,
@@ -113,6 +114,35 @@ def test_value(widget, value, expected, validator):
     on_change_handler.assert_called_once_with(widget)
 
 
+def test_validation_order():
+    """Widget value validation is performed in the correct order."""
+    results = {}
+
+    def on_change(widget):
+        results["valid"] = widget.is_valid
+
+    # Define a validator that only accepts numbers
+    text_input = toga.TextInput(on_change=on_change, validators=[Number()])
+
+    # Widget is initially valid with a number
+    text_input.value = "1234"
+
+    # Change handler was invoked and results are checked
+    assert results["valid"]
+
+    # Widget is invalid with text
+    text_input.value = "hello"
+
+    # Change handler was invoked and results are checked
+    assert not results["valid"]
+
+    # Widget is valid again with a number
+    text_input.value = "1234"
+
+    # Confirm final results are True
+    assert results["valid"]
+
+
 @pytest.mark.parametrize(
     "value, expected",
     [

docs/reference/api/widgets/textinput.rst

@@ -71,6 +71,8 @@ The input can also be provided a list of :ref:`validators <validators>`. A
 validator is a function that will be invoked whenever the content of the input
 changes. The function should return ``None`` if the current value of the input
 is valid; if the current value is invalid, it should return an error message.
+When ``on_change`` is invoked, the field will automatically be validated based on
+specified validators.
 
 Notes
 -----

dummy/src/toga_dummy/widgets/textinput.py

@@ -36,8 +36,7 @@ def is_valid(self):
         return self._get_value("valid")
 
     def simulate_change(self):
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def simulate_confirm(self):
         self.interface.on_confirm()

gtk/src/toga_gtk/widgets/textinput.py

@@ -16,8 +16,7 @@ def create(self):
         self.native.connect("key-press-event", self.gtk_key_press_event)
 
     def gtk_on_change(self, entry):
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def gtk_focus_in_event(self, entry, user_data):
         self.interface.on_gain_focus()

iOS/src/toga_iOS/widgets/textinput.py

@@ -29,8 +29,7 @@ def textFieldDidBeginEditing_(self, textField) -> None:
 
     @objc_method
     def textFieldDidChange_(self, textField) -> None:
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     @objc_method
     def textFieldDidEndEditing_(self, textField) -> None:
@@ -127,8 +126,7 @@ def get_value(self):
 
     def set_value(self, value):
         self.native.text = value
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def set_alignment(self, value):
         self.native.textAlignment = NSTextAlignment(value)

winforms/src/toga_winforms/widgets/textinput.py

@@ -76,8 +76,7 @@ def rehint(self):
         )
 
     def winforms_text_changed(self, sender, event):
-        self.interface.on_change()
-        self.interface._validate()
+        self.interface._value_changed()
 
     def winforms_key_press(self, sender, event):
         if ord(event.KeyChar) == int(WinForms.Keys.Enter):