fix(clone): isolate cloned arrays from source documents - #16281
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vkarpov15 merged 2 commits intoMay 14, 2026
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Pull request overview
This PR fixes a $clone() isolation bug where cloned Mongoose arrays could still be internally parented to the source document, allowing modifications on the clone (and even clone-time population) to mark the original document as modified. The changes ensure cloned document arrays have correct subdocument indexes after source mutations and that both document arrays and primitive arrays don’t leak modification tracking back to the original.
Changes:
- Restamp cloned document-array subdocument indexes during clone array population (while suppressing change tracking).
- Add regression tests to ensure
$clone()doesn’t mutate the original document’smodifiedPaths()for primitive arrays and doesn’t propagate modifications from clone to original. - Add test coverage for cloning document arrays with
nullentries and for index correctness after source array edits.
Reviewed changes
Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.
| File | Description |
|---|---|
| test/document.test.js | Adds regression coverage for clone isolation: subdoc index correctness, null entries in doc arrays, and primitive array modified state isolation. |
| lib/helpers/clone.js | Restamps subdocument indexes during retained document-array cloning while avoiding marking either source or clone modified. |
AbdelrahmanHafez
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May 13, 2026 19:22
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AbdelrahmanHafez
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vkarpov15
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This is great, thanks 👍
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* test(document): cover clone array isolation edge cases * fix(clone): refresh cloned document array indexes
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I also cherry-picked this into 8.x branch. |
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re #15958
$clone()was still leaving one parent pointer connected to the source document. We fixed the parent pointers on cloned subdocs, but retained Mongoose arrays were still constructed with the source document as their internal array parent. That meant cloning could mark the original document modified while populating the clone, and later writes to a cloned array could bubblemarkModified()back to the original.This PR: