Fixed #20098 -- Added a check for model Meta.db_table collisions.

tests/check_framework/test_model_checks.py

@@ -0,0 +1,75 @@
+from django.core import checks
+from django.core.checks import Error
+from django.db import models
+from django.test import SimpleTestCase
+from django.test.utils import (
+    isolate_apps, modify_settings, override_system_checks,
+)
+
+
+@isolate_apps('check_framework', attr_name='apps')
+@override_system_checks([checks.model_checks.check_all_models])
+class DuplicateDBTableTests(SimpleTestCase):
+    def test_collision_in_same_app(self):
+        class Model1(models.Model):
+            class Meta:
+                db_table = 'test_table'
+
+        class Model2(models.Model):
+            class Meta:
+                db_table = 'test_table'
+
+        self.assertEqual(checks.run_checks(app_configs=self.apps.get_app_configs()), [
+            Error(
+                "db_table 'test_table' is used by multiple models: "
+                "check_framework.Model1, check_framework.Model2.",
+                obj='test_table',
+                id='models.E028',
+            )
+        ])
+
+    @modify_settings(INSTALLED_APPS={'append': 'basic'})
+    @isolate_apps('basic', 'check_framework', kwarg_name='apps')
+    def test_collision_across_apps(self, apps):
+        class Model1(models.Model):
+            class Meta:
+                app_label = 'basic'
+                db_table = 'test_table'
+
+        class Model2(models.Model):
+            class Meta:
+                app_label = 'check_framework'
+                db_table = 'test_table'
+
+        self.assertEqual(checks.run_checks(app_configs=apps.get_app_configs()), [
+            Error(
+                "db_table 'test_table' is used by multiple models: "
+                "basic.Model1, check_framework.Model2.",
+                obj='test_table',
+                id='models.E028',
+            )
+        ])
+
+    def test_no_collision_for_unmanaged_models(self):
+        class Unmanaged(models.Model):
+            class Meta:
+                db_table = 'test_table'
+                managed = False
+
+        class Managed(models.Model):
+            class Meta:
+                db_table = 'test_table'
+
+        self.assertEqual(checks.run_checks(app_configs=self.apps.get_app_configs()), [])
+
+    def test_no_collision_for_proxy_models(self):
+        class Model(models.Model):
+            class Meta:
+                db_table = 'test_table'
+
+        class ProxyModel(Model):
+            class Meta:
+                proxy = True
+
+        self.assertEqual(Model._meta.db_table, ProxyModel._meta.db_table)
+        self.assertEqual(checks.run_checks(app_configs=self.apps.get_app_configs()), [])