PYTHON-5782 Coverage increase for `message.py` by aclark4life · Pull Request #2772 · mongodb/mongo-python-driver

aclark4life · 2026-04-23T21:42:44Z

PYTHON-5782

Changes in this PR

Adds test/test_message.py with unit tests for pymongo/message.py.

Tests cover:

Result / error conversion

_convert_exception() — converts an Exception into an errmsg/errtype failure document for event publishing
_convert_client_bulk_exception() — same as above but also captures the error code, used by the client-level bulk write API
_convert_write_result() — converts a legacy GLE (Get Last Error) write result into write-command format, handling insert/update/delete/upsert, wtimeout, and errInfo branches
_raise_document_too_large() — raises DocumentTooLarge with a size-aware message for inserts or a generic message for other operations

Wire-format message construction

_op_msg() — builds an OP_MSG wire message, injecting $db and $readPreference, and temporarily popping document-sequence fields before encoding

Command builders

_gen_find_command() — builds a find command document from a query spec, applying projections, skip/limit, batch size, read concern, collation, and cursor options
_gen_get_more_command() — builds a getMore command document, conditionally including batch size, maxTimeMS, and comment (gated on wire version ≥ 9)

Read preference

_maybe_add_read_preference() — injects $readPreference into a query spec for non-primary modes, skipping plain secondaryPreferred when no tags or maxStalenessSeconds are set

Test Plan

Added unit tests using a real ZlibContext for compression paths and a MagicMock connection for _gen_get_more_command. Focuses on the pure-Python code paths without requiring a live MongoDB server.

hatch run test:test test/test_message.py -v

Checklist

Checklist for Author

Did you update the changelog (if necessary)?
Is there test coverage?
Is any followup work tracked in a JIRA ticket? If so, add link(s).

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Does the title of the PR reference a JIRA Ticket?
Do you fully understand the implementation? (Would you be comfortable explaining how this code works to someone else?)
Is all relevant documentation (README or docstring) updated?

Copilot

Pull request overview

This PR adds a new unit test module to increase coverage of pymongo/message.py by exercising message-building utilities and related pure-Python helper functions without requiring a live MongoDB server.

Changes:

Adds test/test_message.py with unit tests for message helpers (read preference wrapping, command generation, write-result conversion).
Adds tests covering OP_MSG / OP_QUERY / OP_GET_MORE message construction in both compressed and uncompressed paths.
Adds tests for error conversion and document-too-large error formatting.

codecov-commenter · 2026-04-23T22:32:21Z

Codecov Report

✅ All modified and coverable lines are covered by tests.

📢 Thoughts on this report? Let us know!

Copilot

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Copilot reviewed 1 out of 1 changed files in this pull request and generated 3 comments.

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Copilot

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+from pymongo.compression_support import ZlibContext
+from pymongo.errors import DocumentTooLarge, OperationFailure
+from pymongo.message import (
+    _compress,
+    _convert_client_bulk_exception,
+    _convert_exception,
+    _convert_write_result,
+    _gen_find_command,
+    _gen_get_more_command,
+    _get_more_compressed,
+    _get_more_uncompressed,
+    _maybe_add_read_preference,
+    _op_msg,
+    _query_compressed,
+    _query_uncompressed,
+    _raise_document_too_large,
+)


- Replace _MockCtx with real ZlibContext(-1) to satisfy the SnappyContext | ZlibContext | ZstdContext union type - Annotate docs list as list to satisfy the Mapping invariance check - Add # type: ignore[arg-type] on _MockConn call sites for _gen_get_more_command (mocking AsyncConnection | Connection fully would require a much heavier stub)

Copilot

Pull request overview

Copilot reviewed 1 out of 1 changed files in this pull request and generated 2 comments.

+    def test_update_with_upserted_id(self):
+        cmd = {"updates": [{"q": {}, "u": {"_id": 42}}]}
+        result = _convert_write_result("update", cmd, {"n": 1, "upserted": 42})
+        self.assertIn("upserted", result)
+        self.assertEqual(result["upserted"][0]["_id"], 42)
+


+class TestOpMsg(unittest.TestCase):
+    def test_max_doc_size_zero_without_docs(self):
+        max_doc_size = _op_msg(0, {"ping": 1}, "testdb", None, _OPTS)[3]
+        self.assertEqual(max_doc_size, 0)
+


Address Copilot feedback: add tests for legacy upsert _id fallback in _convert_write_result and for the zlib-compressed _op_msg path.

Copilot

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Copilot reviewed 1 out of 1 changed files in this pull request and generated 1 comment.

+    def test_op_msg_compressed_zlib_header(self):
+        # Verify the compressed path is taken and produces a valid OP_COMPRESSED frame.
+        # Header layout (little-endian): [msgLen(4), reqId(4), responseTo(4), opCode(4),
+        #   originalOpcode(4), uncompressedSize(4), compressorId(1)]
+        ctx = ZlibContext(6)
+        _, msg, _, _ = _op_msg(0, {"ping": 1}, "testdb", None, _OPTS, ctx=ctx)


Guard zlib compression test with _have_zlib() skip condition.

Copilot

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Copilot reviewed 1 out of 1 changed files in this pull request and generated no new comments.

aclark4life · 2026-06-10T17:12:18Z

Test failures flaky:

  Error response from daemon: No such image: quay.io/pypa/manylinux_2_28_aarch64:2026.03.20-1
  Error response from daemon: Get "https://quay.io/v2/": context deadline exceeded

(api/gridfs/asynchronous/grid_file: line   10) timeout   http://dochub.mongodb.org/core/gridfsspec - HTTPSConnectionPool(host='dochub.mongodb.org', port=443): Read timed out. (read timeout=60)

NoahStapp · 2026-06-10T17:27:46Z

+        pref = SecondaryPreferred(tag_sets=[{"dc": "east"}])
+        spec: dict = {"find": "col"}
+        result = _maybe_add_read_preference(spec, pref)
+        self.assertIn("$readPreference", result)


This should make the same assertions as test_secondary_adds_read_preference for consistency.

NoahStapp · 2026-06-10T17:29:24Z

+        self.assertEqual(result["upserted"][0]["_id"], 42)
+
+    def test_update_legacy_upsert_id_from_update_doc(self):
+        # Pre-2.6 servers omit "upserted"; _id is extracted from the update doc (takes


We don't support servers <4.2, so no need to test them. Any code that still makes a distinction should be removed.

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aclark4life force-pushed the PYTHON-5782 branch from 45f0c94 to bde1957 Compare May 6, 2026 01:26

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aclark4life changed the title ~~PYTHON-5782 Increase code coverage for message.py~~ PYTHON-5782 Improve code coverage for message.py May 7, 2026

aclark4life changed the title ~~PYTHON-5782 Improve code coverage for message.py~~ PYTHON-5782 Improve coverage for message.py May 7, 2026

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aclark4life changed the title ~~PYTHON-5782 Improve coverage for message.py~~ PYTHON-5782 Improve coverage for message.py May 7, 2026

aclark4life changed the title ~~PYTHON-5782 Improve coverage for message.py~~ PYTHON-5782 Coverage improvements for message.py May 7, 2026

aclark4life changed the title ~~PYTHON-5782 Coverage improvements for message.py~~ PYTHON-5782 Coverage improvement for message.py May 7, 2026

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aclark4life changed the title ~~PYTHON-5782 Coverage improvement for message.py~~ PYTHON-5782 Coverage increase for message.py May 7, 2026

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aclark4life force-pushed the PYTHON-5782 branch 3 times, most recently from 98ecc43 to 3ab7aa5 Compare June 9, 2026 23:53

aclark4life added 6 commits June 10, 2026 12:21

PYTHON-5782 Increase code coverage for message.py from 76.87% to >=80%

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Consolidate 7 classes into one

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aclark4life force-pushed the PYTHON-5782 branch from 3ab7aa5 to 0b1e907 Compare June 10, 2026 16:39

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Address Copilot feedback: add tests for legacy upsert _id fallback in _convert_write_result and for the zlib-compressed _op_msg path.

aclark4life requested a review from Copilot June 10, 2026 16:55

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Guard zlib compression test with _have_zlib() skip condition.

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