[1.7.x] Fixed #22502 -- Fixed microseconds/default/form interaction

Made explicit lack of microsecond handling by built-in datetime form
fields. Used that explicitness to appropriately nix microsecond
values in bound fields. Thanks Claude Paroz for the review.
Backport of a5de0df5 from master.

AUTHORS

@@ -136,6 +136,7 @@ answer newbie questions, and generally made Django that much better:
     btoll@bestweb.net
     Jonathan Buchanan <jonathan.buchanan@gmail.com>
     Jacob Burch <jacobburch@gmail.com>
+    Stephen Burrows <stephen.r.burrows@gmail.com>
     Max Burstein <http://maxburstein.com>
     Keith Bussell <kbussell@gmail.com>
     C8E

django/forms/forms.py

@@ -6,6 +6,7 @@ from __future__ import unicode_literals
 
 from collections import OrderedDict
 import copy
+import datetime
 import warnings
 
 from django.core.exceptions import ValidationError, NON_FIELD_ERRORS
@@ -590,6 +591,11 @@ class BoundField(object):
             data = self.form.initial.get(self.name, self.field.initial)
             if callable(data):
                 data = data()
+                # If this is an auto-generated default date, nix the
+                # microseconds for standardized handling. See #22502.
+                if (isinstance(data, (datetime.datetime, datetime.time)) and
+                        not getattr(self.field.widget, 'supports_microseconds', True)):
+                    data = data.replace(microsecond=0)
         else:
             data = self.field.bound_data(
                 self.data, self.form.initial.get(self.name, self.field.initial)

django/forms/widgets.py

@@ -429,6 +429,7 @@ class Textarea(Widget):
 
 class DateTimeBaseInput(TextInput):
     format_key = ''
+    supports_microseconds = False
 
     def __init__(self, attrs=None, format=None):
         super(DateTimeBaseInput, self).__init__(attrs)
@@ -863,6 +864,7 @@ class SplitDateTimeWidget(MultiWidget):
     """
     A Widget that splits datetime input into two <input type="text"> boxes.
     """
+    supports_microseconds = False
 
     def __init__(self, attrs=None, date_format=None, time_format=None):
         widgets = (DateInput(attrs=attrs, format=date_format),

tests/forms_tests/tests/test_forms.py

@@ -10,10 +10,10 @@ from django.core.files.uploadedfile import SimpleUploadedFile
 from django.core.validators import RegexValidator
 from django.forms import (
     BooleanField, CharField, CheckboxSelectMultiple, ChoiceField, DateField,
-    EmailField, FileField, FloatField, Form, forms, HiddenInput, IntegerField,
-    MultipleChoiceField, MultipleHiddenInput, MultiValueField,
+    DateTimeField, EmailField, FileField, FloatField, Form, forms, HiddenInput,
+    IntegerField, MultipleChoiceField, MultipleHiddenInput, MultiValueField,
     NullBooleanField, PasswordInput, RadioSelect, Select, SplitDateTimeField,
-    Textarea, TextInput, ValidationError, widgets,
+    Textarea, TextInput, TimeField, ValidationError, widgets
 )
 from django.forms.utils import ErrorList
 from django.http import QueryDict
@@ -1287,6 +1287,29 @@ class FormsTestCase(TestCase):
         self.assertEqual(bound['password'].value(), 'foo')
         self.assertEqual(unbound['password'].value(), None)
 
+    def test_initial_datetime_values(self):
+        now = datetime.datetime.now()
+        # Nix microseconds (since they should be ignored). #22502
+        now_no_ms = now.replace(microsecond=0)
+        if now == now_no_ms:
+            now = now.replace(microsecond=1)
+
+        def delayed_now():
+            return now
+
+        def delayed_now_time():
+            return now.time()
+
+        class DateTimeForm(Form):
+            auto_timestamp = DateTimeField(initial=delayed_now)
+            auto_time_only = TimeField(initial=delayed_now_time)
+            supports_microseconds = DateTimeField(initial=delayed_now, widget=TextInput)
+
+        unbound = DateTimeForm()
+        self.assertEqual(unbound['auto_timestamp'].value(), now_no_ms)
+        self.assertEqual(unbound['auto_time_only'].value(), now_no_ms.time())
+        self.assertEqual(unbound['supports_microseconds'].value(), now)
+
     def test_help_text(self):
         # You can specify descriptive text for a field by using the 'help_text' argument)
         class UserRegistration(Form):