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

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):
     """