fix(shared): fix deepMerge data-corruption bugs and add tests

[kridaydave]

Fixes two deepMerge bugs: it destroyed Date/Map/class-instance values (prototype loss) and silently discarded the entire base on a primitive patch.

• Only recurse into plain objects now; Date/Map/instances are overwritten whole.
• Throw on a primitive patch instead of dropping the base (null still allowed).
• Added regression tests in Struct.test.ts and Struct.edgeCases.test.ts.

All gates green (typecheck, check, test).

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Note

Medium Risk
Shared utility behavior change: callers that passed a non-null primitive or array as the top-level patch will now throw instead of getting a silent wrong result; merge semantics for non-plain nested values also change.

Overview
deepMerge in Struct.ts now recurses only when both sides are plain objects (Object.prototype), so Date, Map, class instances, arrays, and functions are replaced wholesale instead of being walked like nested records (which broke Date prototypes and similar values).

Invalid top-level patches throw instead of silently returning a primitive and dropping the base object; null at the top level is still allowed.

New Struct.test.ts and Struct.edgeCases.test.ts lock in normal merge behavior and document remaining quirks (array overwrite, null not skipped, shallow copy of nested refs).

^{Reviewed by Cursor Bugbot for commit 3405a01. Bugbot is set up for automated code reviews on this repo. Configure here.}

Note

Fix data-corruption bugs in deepMerge and add test coverage

• Introduces isPlainObject in Struct.ts to restrict recursion to plain objects; dates, maps, and class instances are now overwritten rather than recursively merged.
• deepMerge now throws when the top-level patch is a non-null primitive (e.g. number, array, function) instead of silently returning it.
• Adds primary tests in Struct.test.ts and edge-case tests in Struct.edgeCases.test.ts documenting both corrected and remaining lossy behaviors.
• Behavioral Change: callers passing a primitive or array as the top-level patch will now receive a thrown error instead of a silent no-op overwrite.

^{Macroscope summarized 3405a01.}

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[macroscopeapp]

Approvability

Verdict: Needs human review

This bug fix introduces meaningful runtime behavior changes to a shared deepMerge utility: new exception pathways for primitive patches and changed merge semantics for Date/Map/class instances. These changes to shared infrastructure warrant human review to ensure callers aren't affected.

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[t3dotgg]

Note

🤖 GPT-6 Astra (preview) responding on behalf of Theo

This was closed as part of an automated cleanup pass. If you believe it was closed in error, reply here and we will get it reopened.

Closing because this change does not address a demonstrated settings failure. Current callers merge schema-validated settings objects, not class instances or primitive patches. The new shared throw changes behavior for inputs outside that settings path. A failing case through a supported settings path would justify a focused fix.