Fixed #18468 -- Added support for comments on columns and tables.

Thanks Jared Chung, Tom Carrick, David Smith, Nick Pope, and Mariusz
Felisiak for reviews.

Co-authored-by: Mariusz Felisiak <felisiak.mariusz@gmail.com>
Co-authored-by: Nick Pope <nick@nickpope.me.uk>

3 files changed, 71 insertions, 1 deletions

diff --git a/tests/invalid_models_tests/test_models.py b/tests/invalid_models_tests/test_models.py
index 5a5aeccdf5..c07c83d79d 100644
--- a/tests/invalid_models_tests/test_models.py
+++ b/tests/invalid_models_tests/test_models.py
@@ -1872,6 +1872,37 @@ class OtherModelTests(SimpleTestCase):
         )
 
 
+@isolate_apps("invalid_models_tests")
+class DbTableCommentTests(TestCase):
+    def test_db_table_comment(self):
+        class Model(models.Model):
+            class Meta:
+                db_table_comment = "Table comment"
+
+        errors = Model.check(databases=self.databases)
+        expected = (
+            []
+            if connection.features.supports_comments
+            else [
+                Warning(
+                    f"{connection.display_name} does not support comments on tables "
+                    f"(db_table_comment).",
+                    obj=Model,
+                    id="models.W046",
+                ),
+            ]
+        )
+        self.assertEqual(errors, expected)
+
+    def test_db_table_comment_required_db_features(self):
+        class Model(models.Model):
+            class Meta:
+                db_table_comment = "Table comment"
+                required_db_features = {"supports_comments"}
+
+        self.assertEqual(Model.check(databases=self.databases), [])
+
+
 class MultipleAutoFieldsTests(TestCase):
     def test_multiple_autofields(self):
         msg = (
diff --git a/tests/invalid_models_tests/test_ordinary_fields.py b/tests/invalid_models_tests/test_ordinary_fields.py
index ef7f845a33..4e07c95956 100644
--- a/tests/invalid_models_tests/test_ordinary_fields.py
+++ b/tests/invalid_models_tests/test_ordinary_fields.py
@@ -1023,3 +1023,35 @@ class JSONFieldTests(TestCase):
             field = models.JSONField(default=callable_default)
 
         self.assertEqual(Model._meta.get_field("field").check(), [])
+
+
+@isolate_apps("invalid_models_tests")
+class DbCommentTests(TestCase):
+    def test_db_comment(self):
+        class Model(models.Model):
+            field = models.IntegerField(db_comment="Column comment")
+
+        errors = Model._meta.get_field("field").check(databases=self.databases)
+        expected = (
+            []
+            if connection.features.supports_comments
+            else [
+                DjangoWarning(
+                    f"{connection.display_name} does not support comments on columns "
+                    f"(db_comment).",
+                    obj=Model._meta.get_field("field"),
+                    id="fields.W163",
+                ),
+            ]
+        )
+        self.assertEqual(errors, expected)
+
+    def test_db_comment_required_db_features(self):
+        class Model(models.Model):
+            field = models.IntegerField(db_comment="Column comment")
+
+            class Meta:
+                required_db_features = {"supports_comments"}
+
+        errors = Model._meta.get_field("field").check(databases=self.databases)
+        self.assertEqual(errors, [])
diff --git a/tests/invalid_models_tests/test_relative_fields.py b/tests/invalid_models_tests/test_relative_fields.py
index 5b4bb45ff8..075bbaefbc 100644
--- a/tests/invalid_models_tests/test_relative_fields.py
+++ b/tests/invalid_models_tests/test_relative_fields.py
@@ -94,7 +94,9 @@ class RelativeFieldTests(SimpleTestCase):
             name = models.CharField(max_length=20)
 
         class ModelM2M(models.Model):
-            m2m = models.ManyToManyField(Model, null=True, validators=[lambda x: x])
+            m2m = models.ManyToManyField(
+                Model, null=True, validators=[lambda x: x], db_comment="Column comment"
+            )
 
         field = ModelM2M._meta.get_field("m2m")
         self.assertEqual(
@@ -110,6 +112,11 @@ class RelativeFieldTests(SimpleTestCase):
                     obj=field,
                     id="fields.W341",
                 ),
+                DjangoWarning(
+                    "db_comment has no effect on ManyToManyField.",
+                    obj=field,
+                    id="fields.W346",
+                ),
             ],
         )