Fixed #26238 -- Raised explicit error for non-editable field in ModelForm

Thanks Luke Crouch for the report and Simon Charette for the review.

django/forms/models.py

@@ -148,6 +148,12 @@ def fields_for_model(model, fields=None, exclude=None, widgets=None,
                                if isinstance(f, ModelField)]
     for f in sorted(chain(opts.concrete_fields, sortable_virtual_fields, opts.many_to_many)):
         if not getattr(f, 'editable', False):
+            if (fields is not None and f.name in fields and
+                    (exclude is None or f.name not in exclude)):
+                raise FieldError(
+                    "'%s' cannot be specified for %s model form as it is a non-editable field" % (
+                        f.name, model.__name__)
+                )
             continue
         if fields is not None and f.name not in fields:
             continue

docs/ref/models/fields.txt

@@ -415,7 +415,8 @@ guaranteed to fit numbers from ``-9223372036854775808`` to
 
 A field to store raw binary data. It only supports ``bytes`` assignment. Be
 aware that this field has limited functionality. For example, it is not possible
-to filter a queryset on a ``BinaryField`` value.
+to filter a queryset on a ``BinaryField`` value. It is also not possible to
+include a ``BinaryField`` in a :class:`~django.forms.ModelForm`.
 
 .. admonition:: Abusing ``BinaryField``
 

tests/model_forms/tests.py

@@ -2282,6 +2282,21 @@ class ModelOtherFieldTests(SimpleTestCase):
         self.assertTrue(HomepageForm({'url': 'http://www.example.com:8000/test'}).is_valid())
         self.assertTrue(HomepageForm({'url': 'http://example.com/foo/bar'}).is_valid())
 
+    def test_modelform_non_editable_field(self):
+        """
+        When explicitely including a non-editable field in a ModelForm, the
+        error message should be explicit.
+        """
+        # 'created', non-editable, is excluded by default
+        self.assertNotIn('created', ArticleForm().fields)
+
+        msg = "'created' cannot be specified for Article model form as it is a non-editable field"
+        with self.assertRaisesMessage(FieldError, msg):
+            class InvalidArticleForm(forms.ModelForm):
+                class Meta:
+                    model = Article
+                    fields = ('headline', 'created')
+
     def test_http_prefixing(self):
         """
         If the http:// prefix is omitted on form input, the field adds it again. (Refs #13613)