fix(form-core): support value types with a custom equals() method in deep equality

[FrancoKaddour]

Closes #2195

Problem

evaluate (the deep-equality helper used for dirty-checking) reports two equal value-type instances as unequal. Value types like Temporal.PlainDate, Luxon DateTime, etc. expose their state through private fields/getters, so they have no own enumerable keys and a non-plain prototype — which hits the no-enumerable-keys guard added in #2140 and returns false. A field backed by such a value is then considered dirty even after it's reset to its original value.

Fix

Before that guard, delegate to a custom equals() method when both operands share a constructor that exposes one. This covers Temporal types, Luxon DateTime, Immutable collections, and any value type following the equals() convention, while leaving plain objects/arrays and the existing Date/Map/Set cases untouched.

Tests

Added a form-core unit test using a value type with a private field and an equals() method (mirroring Temporal's shape — no own enumerable keys). Reverting the fix fails it; the full form-core suite passes, plus typecheck and lint.

Summary by CodeRabbit

• Bug Fixes
  • Improved form value comparisons for objects with custom equals() methods.
  • Added support for value types such as Temporal and Luxon DateTime instances, including objects with private state.
  • Ensured equal instances compare correctly while differing instances remain distinct.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

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Configuration used: defaults

Review profile: CHILL

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Run ID: 364ea4e4-49c0-4609-a420-4ee4bf3e58c2

📥 Commits

Reviewing files that changed from the base of the PR and between 7ed7642 and c424cca.

📒 Files selected for processing (2)

• packages/form-core/src/utils.ts
• packages/form-core/tests/utils.spec.ts

🚧 Files skipped from review as they are similar to previous changes (2)

• packages/form-core/src/utils.ts
• packages/form-core/tests/utils.spec.ts

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📝 Walkthrough

Walkthrough

evaluate now uses callable equals() methods when both objects share a constructor. Tests cover equal and different PlainDate instances and one-sided equals() properties. A patch changeset documents support for custom value types.

Changes

Custom equality support

Layer / File(s)	Summary
Custom equality evaluation packages/form-core/src/utils.ts, packages/form-core/tests/utils.spec.ts, .changeset/evaluate-custom-equals.md	evaluate invokes a callable equals() method before enumerable-key comparison when constructors match. Tests cover matching, nonmatching, and one-sided equals() cases. The changeset documents the patch release.

Estimated code review effort: 2 (Simple) | ~10 minutes

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: support for custom equals methods in form-core deep equality.
Description check	✅ Passed	The description explains the problem, fix, tests, and linked issue, but omits the template checklist and release-impact sections.
Linked Issues check	✅ Passed	The implementation and tests satisfy issue #2195 by using equals() for same-constructor value types, including Temporal-like instances.
Out of Scope Changes check	✅ Passed	The changeset, implementation, and regression tests are directly related to the linked issue and stated pull request objectives.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

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[coderabbitai]

Actionable comments posted: 1

🤖 Prompt for all review comments with AI agents

Verify each finding against current code. Fix only still-valid issues, skip the
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Inline comments:
In `@packages/form-core/src/utils.ts`:
- Around line 522-528: Update the constructor-based equality branch in evaluate
to require both objA.equals and objB.equals to be callable before delegating to
objA.equals(objB). Add a test in utils.spec.ts covering an object with equals()
compared against an object without it, asserting they are not considered equal.

🪄 Autofix (Beta)

Fix all unresolved CodeRabbit comments on this PR:

• Push a commit to this branch (recommended)
• Create a new PR with the fixes

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ℹ️ Review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro Plus

Run ID: 4939f6b5-c10a-44c7-8ff0-7d0e3d405dff

📥 Commits

Reviewing files that changed from the base of the PR and between 5d11281 and 7ed7642.

📒 Files selected for processing (3)

• .changeset/evaluate-custom-equals.md
• packages/form-core/src/utils.ts
• packages/form-core/tests/utils.spec.ts