Chroma 1.5.x can return ``None`` inside the ``metadatas`` / ``documents``
lists of a query/get result for partially-flushed rows. The codebase
already has a systemic None-guard pattern (merged #999, #1013, #1019)
but three call sites were still unguarded:
* ``mcp_server.tool_check_duplicate`` (``mcp_server.py:487-488``) —
``meta = results["metadatas"][0][i]`` followed by ``meta.get(...)``
raises ``AttributeError: 'NoneType' object has no attribute 'get'``.
The broad ``except Exception`` wrapper (line 504) swallows it and
returns an uninformative ``"Duplicate check failed"``.
* ``layers.Layer1.generate`` (``layers.py:126``) — iterates
``zip(docs, metas)`` and calls ``meta.get(key)`` in the importance
loop. A single None metadata blows up the entire wake-up render.
* ``layers.Layer2.retrieve`` (``layers.py:224``) — same pattern, same
crash path for the on-demand render.
Apply the same ``meta = meta or {}`` / ``doc = doc or ""`` idiom used
by the merged guards in the search path. Three-line additions, no
behaviour change on well-formed results.
Tests added:
* ``test_check_duplicate_handles_none_metadata`` — mocks the collection
query to return ``None`` for one metadata and document, asserts the
call does not crash and the sentinel-rendered entry has wing/room "?"
and empty content.
* ``test_layer1_handles_none_metadata`` / ``_handles_none_document``
* ``test_layer2_handles_none_metadata``
Relationship to other open PRs:
* **#1019** guarded ``searcher.py`` loops. This PR extends the same
guard to the three call sites #1019 did not touch.
* **#979** fixed ``tool_check_duplicate`` negative similarity but left
the None-metadata path unguarded.
* Does not overlap **#1013** (``Layer3.search_raw``) or **#999**.
eldar702
4949aab68b