PYTHON-5782 Coverage increase, remove old code in `message.py` by aclark4life · Pull Request #2772 · mongodb/mongo-python-driver

aclark4life · 2026-04-23T21:42:44Z

Changes in this PR

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

Also removes a dead code branch in _convert_write_result() — a legacy compatibility shim for MongoDB < 2.6 that manually reconstructed the upserted _id when it wasn't an ObjectId. MongoDB 2.6+ always returns the upserted field directly, so this branch was unreachable.

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).

Checklist for Reviewer

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

Pull request overview

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

Copilot

Pull request overview

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

Copilot

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

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 · 2026-06-10T17:29:24Z

+        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.

Copilot

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

NoahStapp · 2026-06-11T13:34:42Z

    elif operation == "update":
        if "upserted" in result:
            res["upserted"] = [{"index": 0, "_id": result["upserted"]}]
-        # Versions of MongoDB before 2.6 don't return the _id for an
-        # upsert if _id is not an ObjectId.
-        elif result.get("updatedExisting") is False and affected == 1:
-            # If _id is in both the update document *and* the query spec
-            # the update document _id takes precedence.
-            update = command["updates"][0]
-            _id = update["u"].get("_id", update["q"].get("_id"))
-            res["upserted"] = [{"index": 0, "_id": _id}]
    return res


Agreed that the PR should be updated to reflect that there's this minor refactor here.

NoahStapp · 2026-06-11T13:50:25Z

+
+    # _gen_find_command
+
+    def test_find_basic(self):


All of the calls to _gen_find_command and _gen_get_more_command should use keyword args for readability.

NoahStapp · 2026-06-11T13:52:24Z

+        self.assertEqual(max_doc_size, 0)
+
+    def test_op_msg_max_doc_size_matches_largest_encoded_doc(self):
+        docs = [{"_id": 1, "x": 2}, {"_id": 3, "x": 4}]


These encode to the same size, so the assert would pass regardless of how max_doc_size is set. One of these should be larger than the other to ensure correctness.

NoahStapp · 2026-06-11T13:57:39Z

+        with self.assertRaises(DocumentTooLarge) as ctx:
+            _raise_document_too_large("update", 2_000_000, 1_000_000)
+        self.assertIn("update", str(ctx.exception))


Suggested change

with self.assertRaises(DocumentTooLarge) as ctx:

_raise_document_too_large("update", 2_000_000, 1_000_000)

self.assertIn("update", str(ctx.exception))

with self.assertRaisesRegex(DocumentTooLarge, "update command document too large"):

_raise_document_too_large("update", 2_000_000, 1_000_000)

- 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)

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

Guard zlib compression test with _have_zlib() skip condition.

- Use keyword args in all _gen_find_command and _gen_get_more_command calls - Fix test_op_msg_max_doc_size_matches_largest_encoded_doc to use docs of different sizes so the max() assertion is meaningful - Use assertRaisesRegex with the exact message in test_raise_document_too_large_update_generic_message - Remove !r from the DocumentTooLarge message in _raise_document_too_large so it matches

Copilot

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

        # There's nothing intelligent we can say
        # about size for update and delete
-        raise DocumentTooLarge(f"{operation!r} command document too large")
+        raise DocumentTooLarge(f"{operation} command document too large")


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Copilot AI review requested due to automatic review settings April 23, 2026 21:42

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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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Comment thread test/test_message.py

Comment thread test/test_message.py Outdated

Comment thread test/test_message.py Outdated

aclark4life force-pushed the PYTHON-5782 branch 2 times, most recently from a6c8f8e to a8d9f92 Compare May 6, 2026 20:34

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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 increase for message.py~~ PYTHON-5782 Coverage increase & remove old code in message.py Jun 11, 2026

aclark4life changed the title ~~PYTHON-5782 Coverage increase & remove old code in message.py~~ PYTHON-5782 Coverage increase, remove old code in message.py Jun 11, 2026

aclark4life added 10 commits June 11, 2026 10:57

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

abf0a8b

Noah feedback

57ce025

Jib review

66087b3

Copilot review

f78377f

Claude review

655e89b

Consolidate 7 classes into one

0bef82a

Copilot review

9b68d59

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

Copilot review

e947411

Guard zlib compression test with _have_zlib() skip condition.

Noah feedback

9f89d1b

aclark4life force-pushed the PYTHON-5782 branch from a1c72eb to 9f89d1b Compare June 11, 2026 14:57

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Comment thread pymongo/message.py

# There's nothing intelligent we can say

# about size for update and delete

raise DocumentTooLarge(f"{operation!r} command document too large")

raise DocumentTooLarge(f"{operation} command document too large")

Merge branch 'master' into PYTHON-5782

ce1b47c

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