Refs #30172 -- Prevented removing a field's check or unique constraint from removing Meta constraints.

tests/schema/tests.py

@@ -7,7 +7,8 @@ from unittest import mock
 from django.db import (
     DatabaseError, IntegrityError, OperationalError, connection,
 )
-from django.db.models import Model
+from django.db.models import Model, Q
+from django.db.models.constraints import CheckConstraint, UniqueConstraint
 from django.db.models.deletion import CASCADE, PROTECT
 from django.db.models.fields import (
     AutoField, BigAutoField, BigIntegerField, BinaryField, BooleanField,
@@ -31,9 +32,10 @@ from .fields import (
 from .models import (
     Author, AuthorCharFieldWithIndex, AuthorTextFieldWithIndex,
     AuthorWithDefaultHeight, AuthorWithEvenLongerName, AuthorWithIndexedName,
-    Book, BookForeignObj, BookWeak, BookWithLongName, BookWithO2O,
-    BookWithoutAuthor, BookWithSlug, IntegerPK, Node, Note, NoteRename, Tag,
-    TagIndexed, TagM2MTest, TagUniqueRename, Thing, UniqueTest, new_apps,
+    AuthorWithUniqueName, Book, BookForeignObj, BookWeak, BookWithLongName,
+    BookWithO2O, BookWithoutAuthor, BookWithSlug, IntegerPK, Node, Note,
+    NoteRename, Tag, TagIndexed, TagM2MTest, TagUniqueRename, Thing,
+    UniqueTest, new_apps,
 )
 
 
@@ -1545,6 +1547,53 @@ class SchemaTests(TransactionTestCase):
         if not any(details['columns'] == ['height'] and details['check'] for details in constraints.values()):
             self.fail("No check constraint for height found")
 
+    @skipUnlessDBFeature('supports_column_check_constraints')
+    def test_remove_field_check_does_not_remove_meta_constraints(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(Author)
+        # Add the custom check constraint
+        constraint = CheckConstraint(check=Q(height__gte=0), name='author_height_gte_0_check')
+        custom_constraint_name = constraint.name
+        Author._meta.constraints = [constraint]
+        with connection.schema_editor() as editor:
+            editor.add_constraint(Author, constraint)
+        # Ensure the constraints exist
+        constraints = self.get_constraints(Author._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['height'] and details['check'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 1)
+        # Alter the column to remove field check
+        old_field = Author._meta.get_field('height')
+        new_field = IntegerField(null=True, blank=True)
+        new_field.set_attributes_from_name('height')
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, old_field, new_field, strict=True)
+        constraints = self.get_constraints(Author._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['height'] and details['check'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 0)
+        # Alter the column to re-add field check
+        new_field2 = Author._meta.get_field('height')
+        with connection.schema_editor() as editor:
+            editor.alter_field(Author, new_field, new_field2, strict=True)
+        constraints = self.get_constraints(Author._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['height'] and details['check'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 1)
+        # Drop the check constraint
+        with connection.schema_editor() as editor:
+            Author._meta.constraints = []
+            editor.remove_constraint(Author, constraint)
+
     def test_unique(self):
         """
         Tests removing and adding unique constraints to a single column.
@@ -1671,6 +1720,53 @@ class SchemaTests(TransactionTestCase):
         with self.assertRaises(IntegrityError):
             Tag.objects.create(title='bar', slug='foo')
 
+    @skipUnlessDBFeature('allows_multiple_constraints_on_same_fields')
+    def test_remove_field_unique_does_not_remove_meta_constraints(self):
+        with connection.schema_editor() as editor:
+            editor.create_model(AuthorWithUniqueName)
+        # Add the custom unique constraint
+        constraint = UniqueConstraint(fields=['name'], name='author_name_uniq')
+        custom_constraint_name = constraint.name
+        AuthorWithUniqueName._meta.constraints = [constraint]
+        with connection.schema_editor() as editor:
+            editor.add_constraint(AuthorWithUniqueName, constraint)
+        # Ensure the constraints exist
+        constraints = self.get_constraints(AuthorWithUniqueName._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['name'] and details['unique'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 1)
+        # Alter the column to remove field uniqueness
+        old_field = AuthorWithUniqueName._meta.get_field('name')
+        new_field = CharField(max_length=255)
+        new_field.set_attributes_from_name('name')
+        with connection.schema_editor() as editor:
+            editor.alter_field(AuthorWithUniqueName, old_field, new_field, strict=True)
+        constraints = self.get_constraints(AuthorWithUniqueName._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['name'] and details['unique'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 0)
+        # Alter the column to re-add field uniqueness
+        new_field2 = AuthorWithUniqueName._meta.get_field('name')
+        with connection.schema_editor() as editor:
+            editor.alter_field(AuthorWithUniqueName, new_field, new_field2, strict=True)
+        constraints = self.get_constraints(AuthorWithUniqueName._meta.db_table)
+        self.assertIn(custom_constraint_name, constraints)
+        other_constraints = [
+            name for name, details in constraints.items()
+            if details['columns'] == ['name'] and details['unique'] and name != custom_constraint_name
+        ]
+        self.assertEqual(len(other_constraints), 1)
+        # Drop the unique constraint
+        with connection.schema_editor() as editor:
+            AuthorWithUniqueName._meta.constraints = []
+            editor.remove_constraint(AuthorWithUniqueName, constraint)
+
     def test_unique_together(self):
         """
         Tests removing and adding unique_together constraints on a model.