test(form-core): cover onMount field errors before field mount

[cyphercodes]

Refs #1366

🎯 Changes

• Adds regression coverage for a form-level validators.onMount returning field errors before the corresponding field has mounted.
• Verifies a subsequently mounted FieldApi receives the onMount field error, records the error source as form, and exposes the flattened error list.

✅ Checklist

• I have followed the steps in the Contributing guide.
• I have tested this code locally with pnpm test:pr.

🚀 Release Impact

• This change affects published code, and I have generated a changeset.
• This change is docs/CI/dev-only (no release).

Summary by CodeRabbit

• Tests
  • Added coverage for fields mounted after form initialization to ensure form-level mount validation errors are preserved and reflected correctly in the field’s error state.

[coderabbitai]

No actionable comments were generated in the recent review. 🎉

ℹ️ Recent review info

⚙️ Run configuration

Configuration used: defaults

Review profile: CHILL

Plan: Pro

Run ID: c2678e20-473f-445e-b5c1-0f05f19d39d3

📥 Commits

Reviewing files that changed from the base of the PR and between 6a73479 and 225878f.

📒 Files selected for processing (1)

• packages/form-core/tests/FormApi.spec.ts

---

📝 Walkthrough

Walkthrough

Adds a test for a field mounted after form mount when the form-level onMount validator returns a field error. The test checks the field’s retained error state, errorSourceMap.onMount, and aggregated errors.

Changes

Form mount error retention

Layer / File(s)	Summary
Late field mount error assertions packages/form-core/tests/FormApi.spec.ts	Adds a FormApi test that mounts the form before the field and verifies the field still reflects the form-level onMount error state.

Estimated code review effort

🎯 1 (Trivial) | ⏱️ ~2 minutes

Poem

🐇 I hopped through the form with a curious grin,
A late field appeared, and the errors stayed in.
onMount whispered loud, and the test said “all right,”
With maps and with lists, the bunny’s delight.

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title accurately summarizes the new regression test for onMount field errors before the field mounts.
Description check	✅ Passed	The description follows the template and includes changes, checklist items, and release impact.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out.

❤️ Share

• X
• Mastodon
• Reddit
• LinkedIn

_{Comment @coderabbitai help to get the list of available commands.}