Fixed #16612 -- Improved has_changed detection for localized field values

Thanks Simon Charette for the review.

django/forms/fields.py

@@ -184,17 +184,13 @@ class Field(object):
         # For purposes of seeing whether something has changed, None is
         # the same as an empty string, if the data or inital value we get
         # is None, replace it w/ ''.
-        if data is None:
-            data_value = ''
-        else:
-            data_value = data
-        if initial is None:
-            initial_value = ''
-        else:
-            initial_value = initial
-        if force_text(initial_value) != force_text(data_value):
+        initial_value = initial if initial is not None else ''
+        try:
+            data = self.to_python(data)
+        except ValidationError:
             return True
-        return False
+        data_value = data if data is not None else ''
+        return initial_value != data_value
 
     def __deepcopy__(self, memo):
         result = copy.copy(self)
@@ -392,12 +388,6 @@ class BaseTemporalField(Field):
     def strptime(self, value, format):
         raise NotImplementedError('Subclasses must define this method.')
 
-    def _has_changed(self, initial, data):
-        try:
-            data = self.to_python(data)
-        except ValidationError:
-            return True
-        return self.to_python(initial) != data
 
 class DateField(BaseTemporalField):
     widget = DateInput

django/forms/forms.py

@@ -345,8 +345,8 @@ class BaseForm(object):
                 else:
                     initial_prefixed_name = self.add_initial_prefix(name)
                     hidden_widget = field.hidden_widget()
-                    initial_value = hidden_widget.value_from_datadict(
-                        self.data, self.files, initial_prefixed_name)
+                    initial_value = field.to_python(hidden_widget.value_from_datadict(
+                        self.data, self.files, initial_prefixed_name))
                 if hasattr(field.widget, '_has_changed'):
                     warnings.warn("The _has_changed method on widgets is deprecated,"
                         " define it at field level instead.",

django/forms/models.py

@@ -1012,6 +1012,11 @@ class ModelChoiceField(ChoiceField):
     def validate(self, value):
         return Field.validate(self, value)
 
+    def _has_changed(self, initial, data):
+        initial_value = initial if initial is not None else ''
+        data_value = data if data is not None else ''
+        return force_text(self.prepare_value(initial_value)) != force_text(data_value)
+
 class ModelMultipleChoiceField(ModelChoiceField):
     """A MultipleChoiceField whose choices are a model QuerySet."""
     widget = SelectMultiple
@@ -1059,3 +1064,14 @@ class ModelMultipleChoiceField(ModelChoiceField):
                 not hasattr(value, '_meta')):
             return [super(ModelMultipleChoiceField, self).prepare_value(v) for v in value]
         return super(ModelMultipleChoiceField, self).prepare_value(value)
+
+    def _has_changed(self, initial, data):
+        if initial is None:
+            initial = []
+        if data is None:
+            data = []
+        if len(initial) != len(data):
+            return True
+        initial_set = set([force_text(value) for value in initial])
+        data_set = set([force_text(value) for value in data])
+        return data_set != initial_set

tests/forms_tests/tests/fields.py

@@ -35,7 +35,9 @@ from decimal import Decimal
 from django.core.files.uploadedfile import SimpleUploadedFile
 from django.forms import *
 from django.test import SimpleTestCase
+from django.utils import formats
 from django.utils import six
+from django.utils import translation
 from django.utils._os import upath
 
 
@@ -256,6 +258,17 @@ class FieldsTests(SimpleTestCase):
         f = FloatField(localize=True)
         self.assertWidgetRendersTo(f, '<input id="id_f" name="f" type="text" />')
 
+    def test_floatfield_changed(self):
+        f = FloatField()
+        n = 4.35
+        self.assertFalse(f._has_changed(n, '4.3500'))
+
+        with translation.override('fr'):
+            with self.settings(USE_L10N=True):
+                f = FloatField(localize=True)
+                localized_n = formats.localize_input(n)  # -> '4,35' in French
+                self.assertFalse(f._has_changed(n, localized_n))
+
     # DecimalField ################################################################
 
     def test_decimalfield_1(self):
@@ -346,6 +359,18 @@ class FieldsTests(SimpleTestCase):
         f = DecimalField(localize=True)
         self.assertWidgetRendersTo(f, '<input id="id_f" name="f" type="text" />')
 
+    def test_decimalfield_changed(self):
+        f = DecimalField(max_digits=2, decimal_places=2)
+        d = Decimal("0.1")
+        self.assertFalse(f._has_changed(d, '0.10'))
+        self.assertTrue(f._has_changed(d, '0.101'))
+
+        with translation.override('fr'):
+            with self.settings(USE_L10N=True):
+                f = DecimalField(max_digits=2, decimal_places=2, localize=True)
+                localized_d = formats.localize_input(d)  # -> '0,1' in French
+                self.assertFalse(f._has_changed(d, localized_d))
+
     # DateField ###################################################################
 
     def test_datefield_1(self):
@@ -404,7 +429,6 @@ class FieldsTests(SimpleTestCase):
         f = DateField(input_formats=[format])
         d = datetime.date(2007, 9, 17)
         self.assertFalse(f._has_changed(d, '17/09/2007'))
-        self.assertFalse(f._has_changed(d.strftime(format), '17/09/2007'))
 
     def test_datefield_strptime(self):
         """Test that field.strptime doesn't raise an UnicodeEncodeError (#16123)"""
@@ -445,14 +469,10 @@ class FieldsTests(SimpleTestCase):
     def test_timefield_changed(self):
         t1 = datetime.time(12, 51, 34, 482548)
         t2 = datetime.time(12, 51)
-        format = '%H:%M'
-        f = TimeField(input_formats=[format])
+        f = TimeField(input_formats=['%H:%M', '%H:%M %p'])
         self.assertTrue(f._has_changed(t1, '12:51'))
         self.assertFalse(f._has_changed(t2, '12:51'))
-
-        format = '%I:%M %p'
-        f = TimeField(input_formats=[format])
-        self.assertFalse(f._has_changed(t2.strftime(format), '12:51 PM'))
+        self.assertFalse(f._has_changed(t2, '12:51 PM'))
 
     # DateTimeField ###############################################################
 
@@ -518,8 +538,6 @@ class FieldsTests(SimpleTestCase):
         f = DateTimeField(input_formats=[format])
         d = datetime.datetime(2006, 9, 17, 14, 30, 0)
         self.assertFalse(f._has_changed(d, '2006 09 17 2:30 PM'))
-        # Initial value may be a string from a hidden input
-        self.assertFalse(f._has_changed(d.strftime(format), '2006 09 17 2:30 PM'))
 
     # RegexField ##################################################################
 

tests/i18n/tests.py

@@ -15,7 +15,7 @@ from django.test.utils import override_settings
 from django.utils import translation
 from django.utils.formats import (get_format, date_format, time_format,
     localize, localize_input, iter_format_modules, get_format_modules,
-    number_format, sanitize_separators)
+    number_format, reset_format_cache, sanitize_separators)
 from django.utils.importlib import import_module
 from django.utils.numberformat import format as nformat
 from django.utils._os import upath
@@ -463,6 +463,7 @@ class FormattingTests(TestCase):
         fr_formats.THOUSAND_SEPARATOR = ''
         fr_formats.FIRST_DAY_OF_WEEK = 0
 
+        reset_format_cache()
         with translation.override('fr'):
             with self.settings(USE_THOUSAND_SEPARATOR=True, THOUSAND_SEPARATOR='!'):
                 self.assertEqual('', get_format('THOUSAND_SEPARATOR'))