fix(connection): snapshot Date in heartbeat handler and flush queue on recovery

[andreialecu]

Summary

Fixes #16183. Two related bugs in the heartbeat staleness check:

• Missing Date snapshot: drivers/node-mongodb-native/connection.js used the global Date.now() in the serverHeartbeatSucceeded handler instead of a snapshotted copy (like lib/connection.js already does). When test frameworks fake globalThis.Date, _lastHeartbeatAt gets a fake timestamp while the readyState getter uses the real Date.now(), causing false staleness detection.

• No recovery path for buffered operations: When a stale heartbeat causes readyState to report disconnected, operations buffer into _queue. When the next heartbeat refreshes _lastHeartbeatAt, readyState returns connected again, but the queue is never flushed because _readyState never actually changed — so no state change event fires and onOpen() is never called. This extracts _flushQueue() from onOpen() and calls it from the heartbeat handler when the connection is no longer stale.

Test plan

• Added test: heartbeat handler uses snapshotted Date, not affected by faked globalThis.Date
• Added test: buffered operations flush when heartbeat refreshes stale connection
• Added test: child db (useDb()) queues also flush on heartbeat recovery
• Existing connection pool sharing tests all pass
• ESLint passes on changed files

[Copilot]

Pull request overview

This PR fixes connection staleness false-positives and ensures buffered operations resume after a stale-heartbeat “recovery”, aligning the node-mongodb-native driver connection behavior with the core Connection implementation and preventing hangs like startSession() timing out under Date-mocking test frameworks.

Changes:

• Snapshot globalThis.Date in lib/drivers/node-mongodb-native/connection.js so heartbeat timestamps use the real clock even if globalThis.Date is later faked.
• Flush buffered connection operations from the heartbeat success handler when a previously-stale connection becomes non-stale again (including useDb() child connections).
• Extract queue-flushing into Connection.prototype._flushQueue() and add tests covering the fixed scenarios.

Reviewed changes

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

File	Description
test/connection.test.js	Adds regression tests for Date snapshotting and queue flushing on heartbeat recovery (including child dbs).
lib/drivers/node-mongodb-native/connection.js	Snapshots Date and flushes _queue / child queues on serverHeartbeatSucceeded when the connection is no longer stale.
lib/connection.js	Refactors onOpen() to call a new _flushQueue() helper method.

[vkarpov15]

Good catch, thanks 👍