fix: allow fetch responses from deleted users (#57)

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# Description

This PR allows returning records with deleted users' responses
(user_id=None). This change will allow SDK admins to work with those
responses.


**Type of change**

(Please delete options that are not relevant. Remember to title the PR
according to the type of change)

- [X] Bug fix (non-breaking change which fixes an issue)
- [ ] Breaking change (fix or feature that would cause existing
functionality to not work as expected)

**How Has This Been Tested**

(Please describe the tests that you ran to verify your changes. And
ideally, reference `tests`)

Tested locally

- [ ] Test A
- [ ] Test B

**Checklist**

- [X] I followed the style guidelines of this project
- [ ] I did a self-review of my code
- [ ] My changes generate no new warnings
- [X] I have added tests that prove my fix is effective or that my
feature works
- [ ] I filled out [the contributor form](https://tally.so/r/n9XrxK)
(see text above)
- [X] I have added relevant notes to the `CHANGELOG.md` file (See
https://keepachangelog.com/)

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

CHANGELOG.md

@@ -16,6 +16,10 @@ These are the section headers that we use:
 
 ## [Unreleased]()
 
+### Fixed
+
+- Fixed error when returning responses from deleted users (which contains user_id=None). ([#57](https://github.com/argilla-io/argilla-server/pull/57))
+
 ## [1.25.0](https://github.com/argilla-io/argilla-server/compare/v1.24.0...v1.25.0)
 
 >[!IMPORTANT]

src/argilla_server/schemas/v1/responses.py

@@ -49,7 +49,7 @@ class Response(BaseModel):
     values: Optional[Dict[str, ResponseValue]]
     status: ResponseStatus
     record_id: UUID
-    user_id: UUID
+    user_id: Optional[UUID] = None  # Responses for delete users will have this field as None but still be present
     inserted_at: datetime
     updated_at: datetime
 

tests/unit/api/v1/test_datasets.py

@@ -91,6 +91,7 @@
     LabelSelectionQuestionFactory,
     MetadataPropertyFactory,
     MultiLabelSelectionQuestionFactory,
+    OwnerFactory,
     QuestionFactory,
     RatingQuestionFactory,
     RecordFactory,
@@ -5459,3 +5460,36 @@ async def create_dataset_with_user_responses(
         ]
 
         return dataset, questions, records, responses, suggestions
+
+    async def test_get_record_with_response_for_deleted_user(
+        self,
+        async_client: "AsyncClient",
+        db: "AsyncSession",
+        mock_search_engine: "SearchEngine",
+        owner: User,
+        owner_auth_header: dict,
+    ):
+        record = await RecordFactory.create()
+        user = await OwnerFactory.create()
+        response = await ResponseFactory.create(record=record, user=user)
+
+        mock_search_engine.search.return_value = SearchResponses(
+            items=[SearchResponseItem(record_id=record.id)], total=1
+        )
+
+        await db.delete(user)
+
+        http_response = await async_client.get(
+            f"/api/v1/datasets/{record.dataset.id}/records",
+            params={"include": ["responses"]},
+            headers=owner_auth_header,
+        )
+
+        response_json = http_response.json()
+        assert http_response.status_code == 200
+
+        response_items = response_json["items"]
+        assert len(response_items) == 1
+        assert response_items[0]["id"] == str(record.id)
+        assert response_items[0]["responses"][0]["id"] == str(response.id)
+        assert response_items[0]["responses"][0]["user_id"] is None

tests/unit/api/v1/test_records.py

@@ -13,15 +13,15 @@
 #  limitations under the License.
 
 from datetime import datetime
-from typing import TYPE_CHECKING, Any, Callable, Type
+from typing import TYPE_CHECKING, Any, Awaitable, Callable, Type
 from unittest.mock import call
 from uuid import UUID, uuid4
 
 import pytest
 from argilla_server.constants import API_KEY_HEADER_NAME
 from argilla_server.enums import ResponseStatus
 from argilla_server.models import Dataset, Record, Response, Suggestion, User, UserRole
-from argilla_server.search_engine import SearchEngine
+from argilla_server.search_engine import SearchEngine, SearchResponseItem, SearchResponses
 from sqlalchemy import func, select
 from sqlalchemy.orm import Session
 
@@ -922,7 +922,7 @@ async def test_create_record_response_with_wrong_response_value(
         self,
         async_client: "AsyncClient",
         owner_auth_header: dict,
-        create_questions_func: Callable[["Dataset"], None],
+        create_questions_func: Callable[["Dataset"], Awaitable[None]],
         responses: dict,
         expected_error_msg: str,
     ):