fix(form-core): fix fields being stale on array changes

[LeCarbonator]

Closes #1614
Closes #1561
Closes #1577
Closes #1289

Fixes:

• field.handleChange(undefined) no longer sets the value to the default value
• form.reset() and array methods no longer break controlled input when non-index keys are used
• field values in arrays no longer temporarily become undefined (breaking controlled -> uncontrolled -> controlled)

Todos:

• Test at workplace (known location where previous implementation crashed due to dnd)
• Test performance (what does the rerendering look like now?)
  • children callback
  • Form Composition
• Check other frameworks
  • Solid
  • Angular
  • Vue
  • Svelte
  • Lit

[nx-cloud]

View your CI Pipeline Execution ↗ for commit 53380ba

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nx affected --targets=test:sherif,test:knip,tes...	✅ Succeeded	43s	View ↗
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---

☁️ Nx Cloud last updated this comment at 2025-10-17 12:36:10 UTC

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commit: 53380ba

[codecov]

Codecov Report

❌ Patch coverage is 98.55072% with 1 line in your changes missing coverage. Please review.
✅ Project coverage is 90.61%. Comparing base (6892ed0) to head (53380ba).
⚠️ Report is 29 commits behind head on main.

Files with missing lines	Patch %	Lines
packages/form-core/src/metaHelper.ts	98.21%	1 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1729      +/-   ##
==========================================
+ Coverage   90.35%   90.61%   +0.25%     
==========================================
  Files          38       38              
  Lines        1752     1800      +48     
  Branches      444      460      +16     
==========================================
+ Hits         1583     1631      +48     
- Misses        149      150       +1     
+ Partials       20       19       -1     

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[LeCarbonator]

Notes to self:

Swapping, deletion and basic reset seems to work. However, there's conflicts with the reset that need further investigating.

[changeset-bot]

⚠️ No Changeset found

Latest commit: 53380ba

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[LeCarbonator]

form.reset() still has the issue if the array field's size changes.

swapValues, moveValues and removeValue seem to be fixed.

[LeCarbonator]

form.reset() and array methods are all fixed.

Todos:

• Test at workplace (known location where previous implementation crashed due to dnd)
• Test performance (what does the rerendering look like now?)
  • children callback
  • Form Composition
• Check other frameworks
  • Solid
  • Angular
  • Vue
  • Svelte
  • Lit

[LeCarbonator]

Solid appears to be struggling with this implementation still. I'll look into what can be done to fix it.

[LeCarbonator]

Looks like svelte has a problem when using a keyed list