Fixed #27370 -- Prevented Select widget from using 'required' with a non-empty first value.

AUTHORS

@@ -397,6 +397,7 @@ answer newbie questions, and generally made Django that much better:
     Jorge Bastida <me@jorgebastida.com>
     Jorge Gajon <gajon@gajon.org>
     José Tomás Tocino García <josetomas.tocino@gmail.com>
+    Josef Rousek <josef.rousek@gmail.com>
     Joseph Kocherhans <joseph@jkocherhans.com>
     Josh Smeaton <josh.smeaton@gmail.com>
     Joshua Ginsberg <jag@flowtheory.net>

django/forms/widgets.py

@@ -680,6 +680,28 @@ class Select(ChoiceWidget):
             context['widget']['attrs']['multiple'] = 'multiple'
         return context
 
+    @staticmethod
+    def _choice_has_empty_value(choice):
+        """Return True if the choice's value is empty string or None."""
+        value, _ = choice
+        return (
+            (isinstance(value, six.string_types) and not bool(value)) or
+            value is None
+        )
+
+    def use_required_attribute(self, initial):
+        """
+        Don't render 'required' if the first <option> has a value, as that's
+        invalid HTML.
+        """
+        use_required_attribute = super(Select, self).use_required_attribute(initial)
+        # 'required' is always okay for <select multiple>.
+        if self.allow_multiple_selected:
+            return use_required_attribute
+
+        first_choice = next(iter(self.choices), None)
+        return use_required_attribute and first_choice is not None and self._choice_has_empty_value(first_choice)
+
 
 class NullBooleanSelect(Select):
     """

tests/forms_tests/field_tests/test_choicefield.py

@@ -82,7 +82,7 @@ class ChoiceFieldTest(FormFieldAssertionsMixin, SimpleTestCase):
         f = ChoiceField(choices=[('J', 'John'), ('P', 'Paul')], disabled=True)
         self.assertWidgetRendersTo(
             f,
-            '<select id="id_f" name="f" disabled required><option value="J">John</option>'
+            '<select id="id_f" name="f" disabled><option value="J">John</option>'
             '<option value="P">Paul</option></select>'
         )
 

tests/forms_tests/tests/test_forms.py

@@ -502,12 +502,12 @@ class FormsTestCase(SimpleTestCase):
             language = ChoiceField(choices=[('P', 'Python'), ('J', 'Java')])
 
         f = FrameworkForm(auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select name="language">
 <option value="P">Python</option>
 <option value="J">Java</option>
 </select>""")
         f = FrameworkForm({'name': 'Django', 'language': 'P'}, auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select name="language">
 <option value="P" selected>Python</option>
 <option value="J">Java</option>
 </select>""")
@@ -531,12 +531,12 @@ class FormsTestCase(SimpleTestCase):
             language = ChoiceField(choices=[('P', 'Python'), ('J', 'Java')], widget=Select(attrs={'class': 'foo'}))
 
         f = FrameworkForm(auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language">
 <option value="P">Python</option>
 <option value="J">Java</option>
 </select>""")
         f = FrameworkForm({'name': 'Django', 'language': 'P'}, auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language">
 <option value="P" selected>Python</option>
 <option value="J">Java</option>
 </select>""")
@@ -552,12 +552,12 @@ class FormsTestCase(SimpleTestCase):
             )
 
         f = FrameworkForm(auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language">
 <option value="P">Python</option>
 <option value="J">Java</option>
 </select>""")
         f = FrameworkForm({'name': 'Django', 'language': 'P'}, auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select class="foo" name="language">
 <option value="P" selected>Python</option>
 <option value="J">Java</option>
 </select>""")
@@ -568,10 +568,10 @@ class FormsTestCase(SimpleTestCase):
             language = ChoiceField()
 
         f = FrameworkForm(auto_id=False)
-        self.assertHTMLEqual(str(f['language']), """<select name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select name="language">
 </select>""")
         f.fields['language'].choices = [('P', 'Python'), ('J', 'Java')]
-        self.assertHTMLEqual(str(f['language']), """<select name="language" required>
+        self.assertHTMLEqual(str(f['language']), """<select name="language">
 <option value="P">Python</option>
 <option value="J">Java</option>
 </select>""")
@@ -2363,37 +2363,37 @@ Password: <input type="password" name="password" required />
             is_cool = NullBooleanField()
 
         p = Person({'name': 'Joe'}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1" selected>Unknown</option>
 <option value="2">Yes</option>
 <option value="3">No</option>
 </select>""")
         p = Person({'name': 'Joe', 'is_cool': '1'}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1" selected>Unknown</option>
 <option value="2">Yes</option>
 <option value="3">No</option>
 </select>""")
         p = Person({'name': 'Joe', 'is_cool': '2'}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1">Unknown</option>
 <option value="2" selected>Yes</option>
 <option value="3">No</option>
 </select>""")
         p = Person({'name': 'Joe', 'is_cool': '3'}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1">Unknown</option>
 <option value="2">Yes</option>
 <option value="3" selected>No</option>
 </select>""")
         p = Person({'name': 'Joe', 'is_cool': True}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1">Unknown</option>
 <option value="2" selected>Yes</option>
 <option value="3">No</option>
 </select>""")
         p = Person({'name': 'Joe', 'is_cool': False}, auto_id=False)
-        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool" required>
+        self.assertHTMLEqual(str(p['is_cool']), """<select name="is_cool">
 <option value="1">Unknown</option>
 <option value="2">Yes</option>
 <option value="3" selected>No</option>
@@ -2759,7 +2759,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
             """<li class="required error"><ul class="errorlist"><li>This field is required.</li></ul>
 <label class="required" for="id_name">Name:</label> <input type="text" name="name" id="id_name" required /></li>
 <li class="required"><label class="required" for="id_is_cool">Is cool:</label>
-<select name="is_cool" id="id_is_cool" required>
+<select name="is_cool" id="id_is_cool">
 <option value="1" selected>Unknown</option>
 <option value="2">Yes</option>
 <option value="3">No</option>
@@ -2775,7 +2775,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
 <p class="required error"><label class="required" for="id_name">Name:</label>
 <input type="text" name="name" id="id_name" required /></p>
 <p class="required"><label class="required" for="id_is_cool">Is cool:</label>
-<select name="is_cool" id="id_is_cool" required>
+<select name="is_cool" id="id_is_cool">
 <option value="1" selected>Unknown</option>
 <option value="2">Yes</option>
 <option value="3">No</option>
@@ -2793,7 +2793,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
 <td><ul class="errorlist"><li>This field is required.</li></ul>
 <input type="text" name="name" id="id_name" required /></td></tr>
 <tr class="required"><th><label class="required" for="id_is_cool">Is cool:</label></th>
-<td><select name="is_cool" id="id_is_cool" required>
+<td><select name="is_cool" id="id_is_cool">
 <option value="1" selected>Unknown</option>
 <option value="2">Yes</option>
 <option value="3">No</option>
@@ -3516,7 +3516,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
             '<p><label for="id_f2">F2:</label> <input id="id_f2" maxlength="30" name="f2" type="text" /></p>'
             '<p><label for="id_f3">F3:</label> <textarea cols="40" id="id_f3" name="f3" rows="10" required>'
             '</textarea></p>'
-            '<p><label for="id_f4">F4:</label> <select id="id_f4" name="f4" required>'
+            '<p><label for="id_f4">F4:</label> <select id="id_f4" name="f4">'
             '<option value="P">Python</option>'
             '<option value="J">Java</option>'
             '</select></p>',
@@ -3528,7 +3528,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
             '<li><label for="id_f2">F2:</label> <input id="id_f2" maxlength="30" name="f2" type="text" /></li>'
             '<li><label for="id_f3">F3:</label> <textarea cols="40" id="id_f3" name="f3" rows="10" required>'
             '</textarea></li>'
-            '<li><label for="id_f4">F4:</label> <select id="id_f4" name="f4" required>'
+            '<li><label for="id_f4">F4:</label> <select id="id_f4" name="f4">'
             '<option value="P">Python</option>'
             '<option value="J">Java</option>'
             '</select></li>',
@@ -3542,7 +3542,7 @@ Good luck picking a username that doesn&#39;t already exist.</p>
             '<tr><th><label for="id_f3">F3:</label></th>'
             '<td><textarea cols="40" id="id_f3" name="f3" rows="10" required>'
             '</textarea></td></tr>'
-            '<tr><th><label for="id_f4">F4:</label></th><td><select id="id_f4" name="f4" required>'
+            '<tr><th><label for="id_f4">F4:</label></th><td><select id="id_f4" name="f4">'
             '<option value="P">Python</option>'
             '<option value="J">Java</option>'
             '</select></td></tr>',

tests/forms_tests/tests/tests.py

@@ -109,12 +109,12 @@ class ModelFormCallableModelDefault(TestCase):
         ChoiceOptionModel.objects.create(id=3, name='option 3')
         self.assertHTMLEqual(
             ChoiceFieldForm().as_p(),
-            """<p><label for="id_choice">Choice:</label> <select name="choice" id="id_choice" required>
+            """<p><label for="id_choice">Choice:</label> <select name="choice" id="id_choice">
 <option value="1" selected>ChoiceOption 1</option>
 <option value="2">ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>
 </select><input type="hidden" name="initial-choice" value="1" id="initial-id_choice" /></p>
-<p><label for="id_choice_int">Choice int:</label> <select name="choice_int" id="id_choice_int" required>
+<p><label for="id_choice_int">Choice int:</label> <select name="choice_int" id="id_choice_int">
 <option value="1" selected>ChoiceOption 1</option>
 <option value="2">ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>
@@ -145,12 +145,12 @@ class ModelFormCallableModelDefault(TestCase):
                 'multi_choice': [obj2, obj3],
                 'multi_choice_int': ChoiceOptionModel.objects.exclude(name="default"),
             }).as_p(),
-            """<p><label for="id_choice">Choice:</label> <select name="choice" id="id_choice" required>
+            """<p><label for="id_choice">Choice:</label> <select name="choice" id="id_choice">
 <option value="1">ChoiceOption 1</option>
 <option value="2" selected>ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>
 </select><input type="hidden" name="initial-choice" value="2" id="initial-id_choice" /></p>
-<p><label for="id_choice_int">Choice int:</label> <select name="choice_int" id="id_choice_int" required>
+<p><label for="id_choice_int">Choice int:</label> <select name="choice_int" id="id_choice_int">
 <option value="1">ChoiceOption 1</option>
 <option value="2" selected>ChoiceOption 2</option>
 <option value="3">ChoiceOption 3</option>

tests/forms_tests/widget_tests/test_select.py

@@ -294,3 +294,23 @@ class SelectTest(WidgetTest):
         self.assertIsNot(widget.choices, obj.choices)
         self.assertEqual(widget.attrs, obj.attrs)
         self.assertIsNot(widget.attrs, obj.attrs)
+
+    def test_doesnt_render_required_when_impossible_to_select_empty_field(self):
+        widget = self.widget(choices=[('J', 'John'), ('P', 'Paul')])
+        self.assertIs(widget.use_required_attribute(initial=None), False)
+
+    def test_renders_required_when_possible_to_select_empty_field_str(self):
+        widget = self.widget(choices=[('', 'select please'), ('P', 'Paul')])
+        self.assertIs(widget.use_required_attribute(initial=None), True)
+
+    def test_renders_required_when_possible_to_select_empty_field_list(self):
+        widget = self.widget(choices=[['', 'select please'], ['P', 'Paul']])
+        self.assertIs(widget.use_required_attribute(initial=None), True)
+
+    def test_renders_required_when_possible_to_select_empty_field_none(self):
+        widget = self.widget(choices=[(None, 'select please'), ('P', 'Paul')])
+        self.assertIs(widget.use_required_attribute(initial=None), True)
+
+    def test_doesnt_render_required_when_no_choices_are_available(self):
+        widget = self.widget(choices=[])
+        self.assertIs(widget.use_required_attribute(initial=None), False)

tests/model_forms/tests.py

@@ -2635,11 +2635,11 @@ class OtherModelFormTests(TestCase):
             <p><label for="id_date_published">Date published:</label>
                 <input id="id_date_published" name="date_published" type="text" value="{0}" required />
                 <input id="initial-id_date_published" name="initial-date_published" type="hidden" value="{0}" /></p>
-            <p><label for="id_mode">Mode:</label> <select id="id_mode" name="mode" required>
+            <p><label for="id_mode">Mode:</label> <select id="id_mode" name="mode">
                 <option value="di" selected>direct</option>
                 <option value="de">delayed</option></select>
                 <input id="initial-id_mode" name="initial-mode" type="hidden" value="di" /></p>
-           <p><label for="id_category">Category:</label> <select id="id_category" name="category" required>
+           <p><label for="id_category">Category:</label> <select id="id_category" name="category">
                 <option value="1">Games</option>
                 <option value="2">Comics</option>
                 <option value="3" selected>Novel</option></select>