From e9d1f1182aaccaa8b60cf6a3491f0103d2bb0229 Mon Sep 17 00:00:00 2001
From: MattBlack85 <promat85@gmail.com>
Date: Tue, 18 Nov 2014 15:03:13 +0100
Subject: [PATCH] Fixed #23801 -- Added warning when max_length is used with
 IntegerField

---
 django/db/models/fields/__init__.py           | 17 +++++++++++++++++
 docs/ref/checks.txt                           |  1 +
 .../test_ordinary_fields.py                   | 19 +++++++++++++++++++
 3 files changed, 37 insertions(+)

diff --git a/django/db/models/fields/__init__.py b/django/db/models/fields/__init__.py
index 552f868de2..2c3efbb689 100644
--- a/django/db/models/fields/__init__.py
+++ b/django/db/models/fields/__init__.py
@@ -1704,6 +1704,23 @@ class IntegerField(Field):
     }
     description = _("Integer")
 
+    def check(self, **kwargs):
+        errors = super(IntegerField, self).check(**kwargs)
+        errors.extend(self._check_max_length_warning())
+        return errors
+
+    def _check_max_length_warning(self):
+        if self.max_length is not None:
+            return [
+                checks.Warning(
+                    "'max_length' is ignored when used with IntegerField",
+                    hint="Remove 'max_length' from field",
+                    obj=self,
+                    id='fields.W122',
+                )
+            ]
+        return []
+
     @cached_property
     def validators(self):
         # These validators can't be added at field initialization time since
diff --git a/docs/ref/checks.txt b/docs/ref/checks.txt
index f1b34fade4..86b287c0f2 100644
--- a/docs/ref/checks.txt
+++ b/docs/ref/checks.txt
@@ -82,6 +82,7 @@ Fields
 * **fields.E110**: ``BooleanField``\s do not accept null values.
 * **fields.E120**: ``CharField``\s must define a ``max_length`` attribute.
 * **fields.E121**: ``max_length`` must be a positive integer.
+* **fields.W122**: ``max_length`` is ignored when used with ``IntegerField``.
 * **fields.E130**: ``DecimalField``\s must define a ``decimal_places`` attribute.
 * **fields.E131**: ``decimal_places`` must be a non-negative integer.
 * **fields.E132**: ``DecimalField``\s must define a ``max_digits`` attribute.
diff --git a/tests/invalid_models_tests/test_ordinary_fields.py b/tests/invalid_models_tests/test_ordinary_fields.py
index 90c2026be9..c98d218b09 100644
--- a/tests/invalid_models_tests/test_ordinary_fields.py
+++ b/tests/invalid_models_tests/test_ordinary_fields.py
@@ -513,6 +513,25 @@ class ImageFieldTests(IsolatedModelsTestCase):
         self.assertEqual(errors, expected)
 
 
+class IntegerFieldTests(IsolatedModelsTestCase):
+
+    def test_max_length_warning(self):
+        class Model(models.Model):
+            value = models.IntegerField(max_length=2)
+
+        value = Model._meta.get_field('value')
+        errors = Model.check()
+        expected = [
+            DjangoWarning(
+                "'max_length' is ignored when used with IntegerField",
+                hint="Remove 'max_length' from field",
+                obj=value,
+                id='fields.W122',
+            )
+        ]
+        self.assertEqual(errors, expected)
+
+
 class TimeFieldTests(IsolatedModelsTestCase):
 
     def test_fix_default_value(self):