Fixed #29056 -- Fixed HTML5 validation of required SelectDateWidget.

placeholder is required for "select" with "required" attribute.

django/forms/widgets.py

@@ -979,7 +979,11 @@ class SelectDateWidget(Widget):
         date_context['year'] = self.select_widget(attrs, choices=year_choices).get_context(
             name=year_name,
             value=context['widget']['value']['year'],
-            attrs={**context['widget']['attrs'], 'id': 'id_%s' % year_name},
+            attrs={
+                **context['widget']['attrs'],
+                'id': 'id_%s' % year_name,
+                'placeholder': _('Year') if self.is_required else False,
+            },
         )
         month_choices = list(self.months.items())
         if not self.is_required:
@@ -988,7 +992,11 @@ class SelectDateWidget(Widget):
         date_context['month'] = self.select_widget(attrs, choices=month_choices).get_context(
             name=month_name,
             value=context['widget']['value']['month'],
-            attrs={**context['widget']['attrs'], 'id': 'id_%s' % month_name},
+            attrs={
+                **context['widget']['attrs'],
+                'id': 'id_%s' % month_name,
+                'placeholder': _('Month') if self.is_required else False,
+            },
         )
         day_choices = [(i, i) for i in range(1, 32)]
         if not self.is_required:
@@ -997,7 +1005,11 @@ class SelectDateWidget(Widget):
         date_context['day'] = self.select_widget(attrs, choices=day_choices,).get_context(
             name=day_name,
             value=context['widget']['value']['day'],
-            attrs={**context['widget']['attrs'], 'id': 'id_%s' % day_name},
+            attrs={
+                **context['widget']['attrs'],
+                'id': 'id_%s' % day_name,
+                'placeholder': _('Day') if self.is_required else False,
+            },
         )
         subwidgets = []
         for field in self._parse_date_fmt():

docs/releases/3.0.txt

@@ -373,6 +373,10 @@ Miscellaneous
 
 * Support for ``pywatchman`` < 1.2.0 is removed.
 
+* HTML rendered by :class:`~django.forms.SelectDateWidget` for required fields
+  now have the ``placeholder`` attribute, which mainly may require some
+  adjustments in tests that compare HTML.
+
 .. _deprecated-features-3.0:
 
 Features deprecated in 3.0

tests/forms_tests/widget_tests/test_selectdatewidget.py

@@ -314,6 +314,46 @@ class SelectDateWidgetTest(WidgetTest):
         self.assertFalse(GetNotRequiredDate().fields['mydate'].widget.is_required)
         self.assertTrue(GetRequiredDate().fields['mydate'].widget.is_required)
 
+    def test_selectdate_required_placeholder(self):
+        for required in (True, False):
+            field = DateField(widget=SelectDateWidget(years=('2018', '2019')), required=required)
+            self.check_html(field.widget, 'my_date', '', html=(
+                """
+                <select name="my_date_month" id="id_my_date_month" %(m_placeholder)s>
+                    %(empty)s
+                    <option value="1">January</option>
+                    <option value="2">February</option>
+                    <option value="3">March</option>
+                    <option value="4">April</option>
+                    <option value="5">May</option>
+                    <option value="6">June</option>
+                    <option value="7">July</option>
+                    <option value="8">August</option>
+                    <option value="9">September</option>
+                    <option value="10">October</option>
+                    <option value="11">November</option>
+                    <option value="12">December</option>
+                </select>
+                <select name="my_date_day" id="id_my_date_day" %(d_placeholder)s>
+                    %(empty)s
+                    %(days_options)s
+                </select>
+                <select name="my_date_year" id="id_my_date_year" %(y_placeholder)s>
+                    %(empty)s
+                    <option value="2018">2018</option>
+                    <option value="2019">2019</option>
+                </select>
+                """ % {
+                    'days_options': '\n'.join(
+                        '<option value="%s">%s</option>' % (i, i) for i in range(1, 32)
+                    ),
+                    'm_placeholder': 'placeholder="Month"' if required else '',
+                    'd_placeholder': 'placeholder="Day"' if required else '',
+                    'y_placeholder': 'placeholder="Year"' if required else '',
+                    'empty': '' if required else '<option selected value="">---</option>',
+                }
+            ))
+
     def test_selectdate_empty_label(self):
         w = SelectDateWidget(years=('2014',), empty_label='empty_label')