Add self-referential FK support and additional tests

- Fix transform_sql to update other_column for self-referential FKs
  when the referenced column is being renamed
- Skip FK validation during transform when update_incoming_fks=True
  since self-referential FKs temporarily reference non-existent columns
- Add tests for multiple tables referencing renamed column
- Add test for self-referential FK handling

sqlite_utils/db.py

@@ -1944,19 +1944,29 @@ class Table(Queryable):
                 finally:
                     self.db._skip_fk_validation = False
 
-        sqls = self.transform_sql(
-            types=types,
-            rename=rename,
-            drop=drop,
-            pk=pk,
-            not_null=not_null,
-            defaults=defaults,
-            drop_foreign_keys=drop_foreign_keys,
-            add_foreign_keys=add_foreign_keys,
-            foreign_keys=foreign_keys,
-            column_order=column_order,
-            keep_table=keep_table,
-        )
+        # Skip FK validation for main transform if update_incoming_fks is True
+        # because self-referential FKs will reference the new column name
+        # that only exists after the transform completes
+        if update_incoming_fks and rename:
+            self.db._skip_fk_validation = True
+        try:
+            sqls = self.transform_sql(
+                types=types,
+                rename=rename,
+                drop=drop,
+                pk=pk,
+                not_null=not_null,
+                defaults=defaults,
+                drop_foreign_keys=drop_foreign_keys,
+                add_foreign_keys=add_foreign_keys,
+                foreign_keys=foreign_keys,
+                column_order=column_order,
+                keep_table=keep_table,
+            )
+        finally:
+            if update_incoming_fks and rename:
+                self.db._skip_fk_validation = False
+
         pragma_foreign_keys_was_on = self.db.execute("PRAGMA foreign_keys").fetchone()[
             0
         ]
@@ -2034,6 +2044,9 @@ class Table(Queryable):
             for table, column, other_table, other_column in self.foreign_keys:
                 # Copy over old foreign keys, unless we are dropping them
                 if (drop_foreign_keys is None) or (column not in drop_foreign_keys):
+                    # For self-referential FKs, also update the referenced column if renamed
+                    if other_table == self.name:
+                        other_column = rename.get(other_column) or other_column
                     create_table_foreign_keys.append(
                         ForeignKey(
                             table,

tests/test_transform.py

@@ -708,3 +708,105 @@ def test_transform_update_incoming_fks_on_column_rename(fresh_db):
     assert fresh_db.execute("PRAGMA foreign_keys").fetchone()[0] == 1
     violations = list(fresh_db.execute("PRAGMA foreign_key_check").fetchall())
     assert violations == []
+
+
+def test_transform_update_incoming_fks_multiple_tables(fresh_db):
+    """
+    Test that update_incoming_fks=True updates FK constraints in multiple tables
+    when a referenced column is renamed.
+    """
+    fresh_db.execute("PRAGMA foreign_keys=ON")
+
+    # Create authors table with id as PK
+    fresh_db["authors"].insert({"id": 1, "name": "Alice"}, pk="id")
+
+    # Create multiple tables with FKs to authors.id
+    fresh_db["books"].insert(
+        {"id": 1, "title": "Book A", "author_id": 1},
+        pk="id",
+        foreign_keys=[("author_id", "authors", "id")],
+    )
+    fresh_db["articles"].insert(
+        {"id": 1, "headline": "Article A", "writer_id": 1},
+        pk="id",
+        foreign_keys=[("writer_id", "authors", "id")],
+    )
+    fresh_db["quotes"].insert(
+        {"id": 1, "text": "Quote A", "speaker_id": 1},
+        pk="id",
+        foreign_keys=[("speaker_id", "authors", "id")],
+    )
+
+    # Rename authors.id to authors.author_pk with update_incoming_fks=True
+    fresh_db["authors"].transform(
+        rename={"id": "author_pk"},
+        update_incoming_fks=True,
+    )
+
+    # Verify authors column was renamed
+    assert "author_pk" in fresh_db["authors"].columns_dict
+    assert "id" not in fresh_db["authors"].columns_dict
+
+    # Verify all FKs were updated
+    assert fresh_db["books"].foreign_keys == [
+        ForeignKey(table="books", column="author_id", other_table="authors", other_column="author_pk")
+    ]
+    assert fresh_db["articles"].foreign_keys == [
+        ForeignKey(table="articles", column="writer_id", other_table="authors", other_column="author_pk")
+    ]
+    assert fresh_db["quotes"].foreign_keys == [
+        ForeignKey(table="quotes", column="speaker_id", other_table="authors", other_column="author_pk")
+    ]
+
+    # Verify FK enforcement still works
+    violations = list(fresh_db.execute("PRAGMA foreign_key_check").fetchall())
+    assert violations == []
+
+
+def test_transform_update_incoming_fks_self_referential(fresh_db):
+    """
+    Test that update_incoming_fks=True handles self-referential FK constraints.
+    """
+    fresh_db.execute("PRAGMA foreign_keys=ON")
+
+    # Create employees table with self-referential FK (manager_id -> id)
+    fresh_db.execute("""
+        CREATE TABLE employees (
+            id INTEGER PRIMARY KEY,
+            name TEXT,
+            manager_id INTEGER REFERENCES employees(id)
+        )
+    """)
+    fresh_db["employees"].insert_all([
+        {"id": 1, "name": "CEO", "manager_id": None},
+        {"id": 2, "name": "VP", "manager_id": 1},
+        {"id": 3, "name": "Dev", "manager_id": 2},
+    ])
+
+    # Verify initial FK
+    assert fresh_db["employees"].foreign_keys == [
+        ForeignKey(table="employees", column="manager_id", other_table="employees", other_column="id")
+    ]
+
+    # Rename employees.id to employees.emp_id with update_incoming_fks=True
+    fresh_db["employees"].transform(
+        rename={"id": "emp_id"},
+        update_incoming_fks=True,
+    )
+
+    # Verify column was renamed
+    assert "emp_id" in fresh_db["employees"].columns_dict
+    assert "id" not in fresh_db["employees"].columns_dict
+
+    # Verify self-referential FK was updated
+    assert fresh_db["employees"].foreign_keys == [
+        ForeignKey(table="employees", column="manager_id", other_table="employees", other_column="emp_id")
+    ]
+
+    # Verify data integrity
+    rows = list(fresh_db.execute("SELECT * FROM employees ORDER BY emp_id").fetchall())
+    assert rows == [(1, "CEO", None), (2, "VP", 1), (3, "Dev", 2)]
+
+    # Verify FK enforcement still works
+    violations = list(fresh_db.execute("PRAGMA foreign_key_check").fetchall())
+    assert violations == []