From d381914aef50e04ca44b9d7bb9274c8351f5b9bf Mon Sep 17 00:00:00 2001
From: michaldabski <contact@michaldabski.com>
Date: Thu, 15 Jun 2017 21:44:20 +0100
Subject: [PATCH] Fixed #28313 -- Added model name max length check of 100
 characters in contrib.contentttypes.

---
 django/contrib/contenttypes/apps.py     |  5 ++++-
 django/contrib/contenttypes/checks.py   | 21 +++++++++++++++++++++
 docs/ref/checks.txt                     |  1 +
 tests/contenttypes_tests/test_checks.py | 18 ++++++++++++++++++
 4 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/django/contrib/contenttypes/apps.py b/django/contrib/contenttypes/apps.py
index 095dbf5615..1a8e25b98e 100644
--- a/django/contrib/contenttypes/apps.py
+++ b/django/contrib/contenttypes/apps.py
@@ -1,5 +1,7 @@
 from django.apps import AppConfig
-from django.contrib.contenttypes.checks import check_generic_foreign_keys
+from django.contrib.contenttypes.checks import (
+    check_generic_foreign_keys, check_model_name_lengths,
+)
 from django.core import checks
 from django.db.models.signals import post_migrate, pre_migrate
 from django.utils.translation import gettext_lazy as _
@@ -17,3 +19,4 @@ class ContentTypesConfig(AppConfig):
         pre_migrate.connect(inject_rename_contenttypes_operations, sender=self)
         post_migrate.connect(create_contenttypes)
         checks.register(check_generic_foreign_keys, checks.Tags.models)
+        checks.register(check_model_name_lengths, checks.Tags.models)
diff --git a/django/contrib/contenttypes/checks.py b/django/contrib/contenttypes/checks.py
index d21df40f46..3e802ea26b 100644
--- a/django/contrib/contenttypes/checks.py
+++ b/django/contrib/contenttypes/checks.py
@@ -1,6 +1,7 @@
 from itertools import chain
 
 from django.apps import apps
+from django.core.checks import Error
 
 
 def check_generic_foreign_keys(app_configs=None, **kwargs):
@@ -18,3 +19,23 @@ def check_generic_foreign_keys(app_configs=None, **kwargs):
     for field in fields:
         errors.extend(field.check())
     return errors
+
+
+def check_model_name_lengths(app_configs=None, **kwargs):
+    if app_configs is None:
+        models = apps.get_models()
+    else:
+        models = chain.from_iterable(app_config.get_models() for app_config in app_configs)
+    errors = []
+    for model in models:
+        if len(model._meta.model_name) > 100:
+            errors.append(
+                Error(
+                    'Model names must be at most 100 characters (got %d).' % (
+                        len(model._meta.model_name),
+                    ),
+                    obj=model,
+                    id='contenttypes.E005',
+                )
+            )
+    return errors
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index 64fd6b68aa..b4d1fd4089 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -668,6 +668,7 @@ The following checks are performed when a model contains a
 * **contenttypes.E003**: ``<field>`` is not a ``ForeignKey``.
 * **contenttypes.E004**: ``<field>`` is not a ``ForeignKey`` to
   ``contenttypes.ContentType``.
+* **contenttypes.E005**: Model names must be at most 100 characters.
 
 ``sites``
 ---------
diff --git a/tests/contenttypes_tests/test_checks.py b/tests/contenttypes_tests/test_checks.py
index 6b33107de2..44cd3c2758 100644
--- a/tests/contenttypes_tests/test_checks.py
+++ b/tests/contenttypes_tests/test_checks.py
@@ -1,5 +1,6 @@
 from unittest import mock
 
+from django.contrib.contenttypes.checks import check_model_name_lengths
 from django.contrib.contenttypes.fields import (
     GenericForeignKey, GenericRelation,
 )
@@ -216,3 +217,20 @@ class GenericRelationTests(SimpleTestCase):
                 id='fields.E001',
             )
         ])
+
+
+@isolate_apps('contenttypes_tests', attr_name='apps')
+class ModelCheckTests(SimpleTestCase):
+    def test_model_name_too_long(self):
+        model = type('A' * 101, (models.Model,), {'__module__': self.__module__})
+        self.assertEqual(check_model_name_lengths(self.apps.get_app_configs()), [
+            checks.Error(
+                'Model names must be at most 100 characters (got 101).',
+                obj=model,
+                id='contenttypes.E005',
+            )
+        ])
+
+    def test_model_name_max_length(self):
+        type('A' * 100, (models.Model,), {'__module__': self.__module__})
+        self.assertEqual(check_model_name_lengths(self.apps.get_app_configs()), [])