Gracefully handle Foreign Key Constraint Errors (#4406)

Co-authored-by: Adam Sachs <[email protected]>

CHANGELOG.md

@@ -45,7 +45,9 @@ The types of changes are:
 ## [2.24.0](https://github.com/ethyca/fides/compare/2.23.3...2.24.0)
 
 ### Added
+
 - Adds fides_disable_banner config option to Fides.js [#4378](https://github.com/ethyca/fides/pull/4378)
+- Deletions that fail due to foreign key constraints will now be more clearly communicated [#4406](https://github.com/ethyca/fides/pull/4378)
 - Added support for a custom get preferences API call provided through Fides.init [#4375](https://github.com/ethyca/fides/pull/4375)
 - Hidden custom privacy request fields in the Privacy Center [#4370](https://github.com/ethyca/fides/pull/4370)
 - Backend System-level Cookie Support [#4383](https://github.com/ethyca/fides/pull/4383)
@@ -59,6 +61,7 @@ The types of changes are:
 - Adds more granularity to tracking consent method, updates custom savePreferencesFn and FidesUpdated event to take consent method [#4419](https://github.com/ethyca/fides/pull/4419)
 
 ### Changed
+
 - Add filtering and pagination to bulk vendor add table [#4351](https://github.com/ethyca/fides/pull/4351)
 - Determine if the TCF overlay needs to surface based on backend calculated version hash [#4356](https://github.com/ethyca/fides/pull/4356)
 - Moved Experiences and Preferences endpoints to Plus to take advantage of dynamic GVL  [#4367](https://github.com/ethyca/fides/pull/4367)

src/fides/api/db/crud.py

@@ -5,15 +5,17 @@
 from collections import defaultdict
 from typing import Any, Dict, List, Tuple
 
+from fastapi import HTTPException
 from loguru import logger as log
 from sqlalchemy import and_, column
 from sqlalchemy import delete as _delete
 from sqlalchemy import or_
 from sqlalchemy import update as _update
 from sqlalchemy.dialects.postgresql import Insert as _insert
-from sqlalchemy.exc import SQLAlchemyError
+from sqlalchemy.exc import IntegrityError, SQLAlchemyError
 from sqlalchemy.ext.asyncio import AsyncSession
 from sqlalchemy.future import select
+from starlette.status import HTTP_422_UNPROCESSABLE_ENTITY
 
 from fides.api.db.base import Base  # type: ignore[attr-defined]
 from fides.api.models.sql_models import (  # type: ignore[attr-defined]
@@ -308,6 +310,7 @@ async def delete_resource(
 
         async with async_session.begin():
             try:
+                # Automatically delete related resources if they are CTL objects
                 if hasattr(sql_model, "parent_key"):
                     log.debug("Deleting resource and its children")
                     query = (
@@ -324,6 +327,19 @@ async def delete_resource(
                     log.debug("Deleting resource")
                     query = _delete(sql_model).where(sql_model.fides_key == fides_key)
                 await async_session.execute(query)
+            except IntegrityError as err:
+                raw_error_text: str = err.orig.args[0]
+
+                if "violates foreign key constraint" in raw_error_text:
+                    error_message = "Failed to delete resource! Foreign key constraint found, try deleting related resources first."
+                else:
+                    error_message = "Failed to delete resource!"
+
+                log.bind(error="SQL Query integrity error!").error(raw_error_text)
+                raise HTTPException(
+                    status_code=HTTP_422_UNPROCESSABLE_ENTITY,
+                    detail=error_message,
+                )
             except SQLAlchemyError:
                 error = errors.QueryError()
                 log.bind(error=error.detail["error"]).info(  # type: ignore[index]

tests/ctl/database/test_crud.py

@@ -3,6 +3,7 @@
 from uuid import uuid4
 
 import pytest
+from fastapi import HTTPException
 from sqlalchemy.exc import SQLAlchemyError
 from sqlalchemy.ext.asyncio import AsyncSession
 
@@ -31,7 +32,6 @@ def fixture_created_resources(
     created_keys = []
     resource_type = request.param
     to_create = ["foo", "foo.bar", "foo.bar.baz", "foo.boo"]
-
     for key in to_create:
         parent_key = ".".join(key.split(".")[:-1]) if "." in key else None
 
@@ -73,6 +73,20 @@ async def test_cascade_delete_taxonomy_children(
     assert len(set(keys).intersection(remaining_keys)) == 0
 
 
+@pytest.mark.integration
+async def test_delete_fails_linked_resources(
+    linked_dataset,
+    async_session: AsyncSession,
+) -> None:
+    """Deleting a resource should fail if a linked resource (without cascade delete relationship) still exists."""
+    with pytest.raises(HTTPException) as e:
+        await delete_resource(
+            sql_models.Dataset, linked_dataset.fides_key, async_session
+        )
+
+    assert "try deleting related resources first" in str(e)
+
+
 @pytest.fixture(scope="function")
 def custom_field_definition_data_use(db):
     custom_field_definition_data = {