[1.7.x] Fixed #23674 -- Fixed a crash when a MultiValueField has invalid data.

Backport of 0dea81cd6d34b3e41cc4bbec99b5fdf06142b09e from master

django/forms/fields.py

@@ -1068,7 +1068,11 @@ class MultiValueField(Field):
             if not isinstance(initial, list):
                 initial = self.widget.decompress(initial)
         for field, initial, data in zip(self.fields, initial, data):
-            if field._has_changed(field.to_python(initial), data):
+            try:
+                initial = field.to_python(initial)
+            except ValidationError:
+                return True
+            if field._has_changed(initial, data):
                 return True
         return False
 

docs/releases/1.7.2.txt

@@ -119,3 +119,5 @@ Bugfixes
 * Fixed bug in ``makemigrations`` that created broken migration files when
   dealing with multiple table inheritance and inheriting from more than one
   model (:ticket:`23956`).
+
+* Fixed a crash when a ``MultiValueField`` has invalid data (:ticket:`23674`).

tests/forms_tests/tests/test_forms.py

@@ -1952,6 +1952,22 @@ class FormsTestCase(TestCase):
         self.assertFalse(id(field2.fields[0].choices) ==
                          id(field.fields[0].choices))
 
+    def test_multivalue_initial_data(self):
+        """
+        #23674 -- invalid initial data should not break form.changed_data()
+        """
+        class DateAgeField(MultiValueField):
+            def __init__(self, fields=(), *args, **kwargs):
+                fields = (DateField(label="Date"), IntegerField(label="Age"))
+                super(DateAgeField, self).__init__(fields=fields, *args, **kwargs)
+
+        class DateAgeForm(Form):
+            date_age = DateAgeField()
+
+        data = {"date_age": ["1998-12-06", 16]}
+        form = DateAgeForm(data, initial={"date_age": ["200-10-10", 14]})
+        self.assertTrue(form.has_changed())
+
     def test_multivalue_optional_subfields(self):
         class PhoneField(MultiValueField):
             def __init__(self, *args, **kwargs):