Refs #31055 -- Made long column names checks support databases aware.

django/db/models/base.py

@@ -1258,7 +1258,7 @@ class Model(metaclass=ModelBase):
             errors += [
                 *cls._check_fields(**kwargs),
                 *cls._check_m2m_through_same_relationship(),
-                *cls._check_long_column_names(),
+                *cls._check_long_column_names(databases),
             ]
             clash_errors = (
                 *cls._check_id_field(),
@@ -1763,17 +1763,19 @@ class Model(metaclass=ModelBase):
         return errors
 
     @classmethod
-    def _check_long_column_names(cls):
+    def _check_long_column_names(cls, databases):
         """
         Check that any auto-generated column names are shorter than the limits
         for each database in which the model will be created.
         """
+        if not databases:
+            return []
         errors = []
         allowed_len = None
         db_alias = None
 
         # Find the minimum max allowed length among all specified db_aliases.
-        for db in settings.DATABASES:
+        for db in databases:
             # skip databases where the model won't be created
             if not router.allow_migrate_model(db, cls):
                 continue

tests/invalid_models_tests/test_models.py

@@ -1,6 +1,5 @@
 import unittest
 
-from django.conf import settings
 from django.core.checks import Error, Warning
 from django.core.checks.model_checks import _check_lazy_references
 from django.db import connection, connections, models
@@ -18,7 +17,7 @@ def get_max_column_name_length():
     allowed_len = None
     db_alias = None
 
-    for db in settings.DATABASES:
+    for db in ('default', 'other'):
         connection = connections[db]
         max_name_length = connection.ops.max_name_length()
         if max_name_length is not None and not connection.features.truncates_names:
@@ -408,7 +407,7 @@ class FieldNamesTests(SimpleTestCase):
             db_column=long_field_name
         ).contribute_to_class(m2mcomplex, long_field_name)
 
-        errors = ModelWithLongField.check()
+        errors = ModelWithLongField.check(databases=('default', 'other'))
 
         # First error because of M2M field set on the model with long name.
         m2m_long_name = "verylongmodelnamezzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzzz_id"
@@ -446,6 +445,9 @@ class FieldNamesTests(SimpleTestCase):
         )
 
         self.assertEqual(errors, expected)
+        # Check for long column names is called only for specified database
+        # aliases.
+        self.assertEqual(ModelWithLongField.check(databases=None), [])
 
     @unittest.skipIf(max_column_name_length is None, "The database doesn't have a column name length limit.")
     def test_local_field_long_column_name(self):
@@ -462,7 +464,7 @@ class FieldNamesTests(SimpleTestCase):
         long_field_name2 = 'b' * (self.max_column_name_length + 1)
         models.CharField(max_length=11).contribute_to_class(ModelWithLongField, long_field_name)
         models.CharField(max_length=11, db_column='vlmn').contribute_to_class(ModelWithLongField, long_field_name2)
-        self.assertEqual(ModelWithLongField.check(), [
+        self.assertEqual(ModelWithLongField.check(databases=('default', 'other')), [
             Error(
                 'Autogenerated column name too long for field "%s". '
                 'Maximum length is "%s" for database "%s".'
@@ -472,6 +474,9 @@ class FieldNamesTests(SimpleTestCase):
                 id='models.E018',
             )
         ])
+        # Check for long column names is called only for specified database
+        # aliases.
+        self.assertEqual(ModelWithLongField.check(databases=None), [])
 
     def test_including_separator(self):
         class Model(models.Model):