Fixed #22206 -- Passed models.TextField.max_length to forms.CharField.maxlength

AUTHORS

@@ -666,6 +666,7 @@ answer newbie questions, and generally made Django that much better:
     Rachel Willmer <http://www.willmer.com/kb/>
     Jakub Wilk <ubanus@users.sf.net>
     Ian A Wilson <http://ianawilson.com>
+    Chris Wilson <chris+github@qwirx.com>
     Jakub Wiśniowski <restless.being@gmail.com>
     Maciej Wiśniowski <pigletto@gmail.com>
     wojtek

django/db/models/fields/__init__.py

@@ -1850,7 +1850,10 @@ class TextField(Field):
         return smart_text(value)
 
     def formfield(self, **kwargs):
-        defaults = {'widget': forms.Textarea}
+        # Passing max_length to forms.CharField means that the value's length
+        # will be validated twice. This is considered acceptable since we want
+        # the value in the form field (to pass into widget for example).
+        defaults = {'max_length': self.max_length, 'widget': forms.Textarea}
         defaults.update(kwargs)
         return super(TextField, self).formfield(**defaults)
 

django/forms/fields.py

@@ -223,7 +223,7 @@ class CharField(Field):
 
     def widget_attrs(self, widget):
         attrs = super(CharField, self).widget_attrs(widget)
-        if self.max_length is not None and isinstance(widget, TextInput):
+        if self.max_length is not None:
             # The HTML attribute is maxlength, not max_length.
             attrs.update({'maxlength': str(self.max_length)})
         return attrs

docs/ref/models/fields.txt

@@ -968,6 +968,13 @@ databases supported by Django.
 A large text field. The default form widget for this field is a
 :class:`~django.forms.Textarea`.
 
+.. versionchanged:: 1.7
+
+    If you specify a ``max_length`` attribute, it will be reflected in the
+    :class:`~django.forms.Textarea` widget of the auto-generated form field.
+    However it is not enforced at the model or database level. Use a
+    :class:`CharField` for that.
+
 .. admonition:: MySQL users
 
     If you are using this field with MySQLdb 1.2.1p2 and the ``utf8_bin``

docs/releases/1.7.txt

@@ -488,6 +488,10 @@ Forms
   Each radio button or checkbox includes an ``id_for_label`` attribute to
   output the element's ID.
 
+* The ``<textarea>`` tags rendered by :class:`~django.forms.Textarea` now
+  include a ``maxlength`` attribute if the :class:`~django.db.models.TextField`
+  model field has a ``max_length``.
+
 * :attr:`Field.choices<django.db.models.Field.choices>` now allows you to
   customize the "empty choice" label by including a tuple with an empty string
   or ``None`` for the key and the custom label as the value. The default blank

tests/forms_tests/tests/test_fields.py

@@ -38,7 +38,7 @@ from django.forms import (
     DecimalField, EmailField, Field, FileField, FilePathField, FloatField,
     Form, forms, HiddenInput, IntegerField, MultipleChoiceField,
     NullBooleanField, NumberInput, PasswordInput, RadioSelect, RegexField,
-    SplitDateTimeField, TextInput, TimeField, TypedChoiceField,
+    SplitDateTimeField, TextInput, Textarea, TimeField, TypedChoiceField,
     TypedMultipleChoiceField, URLField, ValidationError, Widget,
 )
 from django.test import SimpleTestCase
@@ -148,14 +148,13 @@ class FieldsTests(SimpleTestCase):
         # Return an empty dictionary if max_length is None
         f = CharField()
         self.assertEqual(f.widget_attrs(TextInput()), {})
-
+        self.assertEqual(f.widget_attrs(Textarea()), {})
-        # Or if the widget is not TextInput or PasswordInput
-        f = CharField(max_length=10)
-        self.assertEqual(f.widget_attrs(HiddenInput()), {})
 
         # Otherwise, return a maxlength attribute equal to max_length
+        f = CharField(max_length=10)
         self.assertEqual(f.widget_attrs(TextInput()), {'maxlength': '10'})
         self.assertEqual(f.widget_attrs(PasswordInput()), {'maxlength': '10'})
+        self.assertEqual(f.widget_attrs(Textarea()), {'maxlength': '10'})
 
     # IntegerField ################################################################
 

tests/model_fields/tests.py

@@ -203,6 +203,21 @@ class BooleanFieldTests(unittest.TestCase):
     def test_nullbooleanfield_to_python(self):
         self._test_to_python(models.NullBooleanField())
 
+    def test_charfield_textfield_max_length_passed_to_formfield(self):
+        """
+        Test that CharField and TextField pass their max_length attributes to
+        form fields created using their .formfield() method (#22206).
+        """
+        cf1 = models.CharField()
+        cf2 = models.CharField(max_length=1234)
+        self.assertIsNone(cf1.formfield().max_length)
+        self.assertEqual(1234, cf2.formfield().max_length)
+
+        tf1 = models.TextField()
+        tf2 = models.TextField(max_length=2345)
+        self.assertIsNone(tf1.formfield().max_length)
+        self.assertEqual(2345, tf2.formfield().max_length)
+
     def test_booleanfield_choices_blank(self):
         """
         Test that BooleanField with choices and defaults doesn't generate a

tests/model_forms/tests.py

@@ -533,7 +533,7 @@ class TestFieldOverridesByFormMeta(TestCase):
         form = FieldOverridesByFormMetaForm()
         self.assertHTMLEqual(
             str(form['name']),
-            '<textarea id="id_name" rows="10" cols="40" name="name"></textarea>',
+            '<textarea id="id_name" rows="10" cols="40" name="name" maxlength="20"></textarea>',
         )
         self.assertHTMLEqual(
             str(form['url']),