fix(api): guard document rename when linked file row is missing (#15536)

## Summary
Fixes #15534 — `update_document_name_only()` crashes with
`AttributeError` when `File2Document` exists but the linked `File` row
was deleted.

`update_document_name_only()` in `document_api_service.py` called
`FileService.get_by_id()` when a `File2Document` row existed, then
accessed `file.id` without checking the lookup result. An orphan
`File2Document` link (file deleted, mapping left behind) caused document
rename via `PATCH /api/v1/datasets/{dataset_id}/documents/{document_id}`
to return HTTP 500.

This PR mirrors guards used in `file2document_api.py` and
`file_api_service.py`: skip the optional file rename when the file is
missing, and still update the document record and search index.

## Changes
- `api/apps/services/document_api_service.py` — check `e and file`
before `FileService.update_by_id`
- `test/unit_test/api/apps/services/test_update_document_name_only.py` —
regression tests (orphan link + happy path)

## Test plan
- [x] `pytest
test/unit_test/api/apps/services/test_update_document_name_only.py -v`
- [ ] Manual: PATCH document `name` when `File2Document` points to a
non-existent `file_id` → 200, document/index renamed, no 500

api/apps/services/document_api_service.py

@@ -39,7 +39,8 @@ def update_document_name_only(document_id, req_doc_name):
     informs = File2DocumentService.get_by_document_id(document_id)
     if informs:
         e, file = FileService.get_by_id(informs[0].file_id)
-        FileService.update_by_id(file.id, {"name": req_doc_name})
+        if e and file:
+            FileService.update_by_id(file.id, {"name": req_doc_name})
     # Add logic to update index - refer to rename method in document_app.py
     tenant_id = DocumentService.get_tenant_id(document_id)
     title_tks = rag_tokenizer.tokenize(req_doc_name)

test/unit_test/api/apps/services/test_update_document_name_only.py

@@ -0,0 +1,145 @@
+#
+#  Copyright 2026 The InfiniFlow Authors. All Rights Reserved.
+#
+#  Licensed under the Apache License, Version 2.0 (the "License");
+#  you may not use this file except in compliance with the License.
+#  You may obtain a copy of the License at
+#
+#      http://www.apache.org/licenses/LICENSE-2.0
+#
+#  Unless required by applicable law or agreed to in writing, software
+#  distributed under the License is distributed on an "AS IS" BASIS,
+#  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+#  See the License for the specific language governing permissions and
+#  limitations under the License.
+#
+"""Regression tests for update_document_name_only() in document_api_service."""
+
+import importlib.util
+import sys
+from pathlib import Path
+from types import ModuleType, SimpleNamespace
+from unittest.mock import MagicMock
+
+import pytest
+
+pytestmark = pytest.mark.p2
+
+
+def _stub(monkeypatch, name, **attrs):
+    mod = ModuleType(name)
+    for key, value in attrs.items():
+        setattr(mod, key, value)
+    monkeypatch.setitem(sys.modules, name, mod)
+    if "." in name:
+        parent_name, _, child_name = name.rpartition(".")
+        parent_mod = sys.modules.get(parent_name)
+        if parent_mod is not None:
+            monkeypatch.setattr(parent_mod, child_name, mod, raising=False)
+    return mod
+
+
+def _load_update_document_name_only_module(monkeypatch, *, file_lookup):
+    file_update = MagicMock()
+    doc_store_update = MagicMock()
+    doc = SimpleNamespace(id="doc-1", kb_id="kb-1")
+    f2d_row = SimpleNamespace(file_id="missing-file-id")
+
+    _stub(
+        monkeypatch,
+        "api.db.services.document_service",
+        DocumentService=SimpleNamespace(
+            update_by_id=lambda doc_id, data: True,
+            get_tenant_id=lambda doc_id: "tenant-1",
+            get_by_id=lambda doc_id: (True, doc),
+        ),
+    )
+    _stub(
+        monkeypatch,
+        "api.db.services.file2document_service",
+        File2DocumentService=SimpleNamespace(
+            get_by_document_id=lambda doc_id: [f2d_row],
+        ),
+    )
+    _stub(
+        monkeypatch,
+        "api.db.services.file_service",
+        FileService=SimpleNamespace(
+            get_by_id=file_lookup,
+            update_by_id=file_update,
+        ),
+    )
+    _stub(
+        monkeypatch,
+        "api.utils.api_utils",
+        get_error_data_result=lambda **kwargs: kwargs,
+        server_error_response=lambda e: {"error": str(e)},
+        get_parser_config=lambda doc: {},
+    )
+    _stub(monkeypatch, "api.utils.validation_utils", UpdateDocumentReq=object)
+    _stub(monkeypatch, "api.utils", validation_utils=sys.modules["api.utils.validation_utils"])
+    _stub(monkeypatch, "common.constants", TaskStatus=SimpleNamespace(RUNNING=SimpleNamespace(value="1")))
+    _stub(
+        monkeypatch,
+        "common.settings",
+        docStoreConn=SimpleNamespace(
+            index_exist=lambda idx, kb_id: True,
+            update=doc_store_update,
+        ),
+    )
+    _stub(
+        monkeypatch,
+        "rag.nlp.search",
+        index_name=lambda tenant_id: f"idx-{tenant_id}",
+    )
+    _stub(
+        monkeypatch,
+        "rag.nlp.rag_tokenizer",
+        tokenize=lambda text: [text],
+        fine_grained_tokenize=lambda tokens: tokens,
+    )
+
+    module_path = (
+        Path(__file__).resolve().parents[5]
+        / "api"
+        / "apps"
+        / "services"
+        / "document_api_service.py"
+    )
+    spec = importlib.util.spec_from_file_location(
+        "test_update_document_name_only_module", module_path
+    )
+    module = importlib.util.module_from_spec(spec)
+    monkeypatch.setitem(sys.modules, "test_update_document_name_only_module", module)
+    spec.loader.exec_module(module)
+    return module, file_update, doc_store_update
+
+
+@pytest.mark.p2
+def test_update_document_name_only_skips_missing_linked_file(monkeypatch):
+    """Orphan File2Document rows must not crash rename with AttributeError."""
+    module, file_update, doc_store_update = _load_update_document_name_only_module(
+        monkeypatch,
+        file_lookup=lambda file_id: (False, None),
+    )
+
+    result = module.update_document_name_only("doc-1", "renamed.pdf")
+
+    assert result is None
+    file_update.assert_not_called()
+    doc_store_update.assert_called_once()
+
+
+@pytest.mark.p2
+def test_update_document_name_only_updates_linked_file_when_present(monkeypatch):
+    linked_file = SimpleNamespace(id="file-1")
+    module, file_update, doc_store_update = _load_update_document_name_only_module(
+        monkeypatch,
+        file_lookup=lambda file_id: (True, linked_file),
+    )
+
+    result = module.update_document_name_only("doc-1", "renamed.pdf")
+
+    assert result is None
+    file_update.assert_called_once_with("file-1", {"name": "renamed.pdf"})
+    doc_store_update.assert_called_once()