Fix #1050: useField returns Form initialValues on first render

[erikras-richard-agent]

Issue: In v7.0.0, useField returns undefined on first render even when Form initialValues are set. This breaks apps trying to upgrade from v6.

Root cause: useField's useState initializer falls back to creating initial state when getFieldState() returns undefined, but only checks field-level initialValue, not the Form's initialValues.

Solution: In the fallback case, check form.getState().initialValues[name] before using field-level initialValue. Form-level initialValues take precedence.

Tests:

• useField returns Form initialValues on first render
• useField uses field initialValue when Form initialValues missing that field
• All existing tests pass (14/14)

This is a clean solution that avoids the side effects of synchronous registration during render (which React forbids).

Closes #1050

Summary by CodeRabbit

• Tests

  • Expanded coverage for field initial-value handling, including nested and array field paths and render-time verification.

• Bug Fixes

  • Fields now prioritize form-level initial values with field-level fallback.
  • Multi-selects initialize to an empty array when no initial value is provided.

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📝 Walkthrough

Walkthrough

Initialization logic in useField was changed to derive the field's initial value from the Form's initialValues (via getIn) before falling back to the field-level initialValue. Tests were added to validate form-level, field-level, nested, and array-path initial value resolution on first render.

Changes

Cohort / File(s)	Summary
Tests src/useField.test.js	Expanded tests to cover initial value resolution: preference for Form initialValues, fallback to field-level initialValue, nested path (user.name) handling, array path (items[0].name) handling, and render-time value assertions via a render spy.
Hook Implementation src/useField.ts	Use getIn(formState.initialValues, name) to source the initial field value before using field initialValue; consolidate initialStateValue logic and ensure multi-select initializes to [] when appropriate.

Estimated code review effort

🎯 3 (Moderate) | ⏱️ ~20 minutes

Poem

🐇 I rummaged through values, near and far,
Found forms and fields both know who they are,
Nested names and arrays align,
No more undefined on first draw—it's fine,
Hooray, a proper initial-value carrot! 🥕

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 0.00% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Description Check	✅ Passed	Check skipped - CodeRabbit’s high-level summary is enabled.
Title check	✅ Passed	The title clearly and concisely describes the main change: fixing useField to return Form initialValues on first render, directly addressing issue #1050.
Linked Issues check	✅ Passed	All coding requirements from issue #1050 are met: useField now reads Form-level initialValues before field-level fallback, returns correct values on first render, uses form.getState().initialValues to avoid side effects during render.
Out of Scope Changes check	✅ Passed	All changes are directly scoped to resolving issue #1050: test coverage for Form initialValues handling and useField production logic modifications are both within scope.

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✨ Finishing touches

🧪 Generate unit tests (beta)

• Create PR with unit tests
• Post copyable unit tests in a comment
• Commit unit tests in branch fix/issue-1050-usefield-initial-value-clean

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[coderabbitai]

Actionable comments posted: 1

🤖 Fix all issues with AI agents

In `@src/useField.ts`:
- Around line 116-125: The lookup for form initial values uses direct property
access (form.getState().initialValues?.[name]) which breaks for path-style names
like "user.name" or "items[0].id"; change it to use Final Form's path-aware
getter (getIn) on the form state initialValues when computing formInitialValue
so formInitialValue = getIn(form.getState().initialValues, name) (falling back
to existing initialValue and preserving the existing select/multiple -> []
handling for initialStateValue). Ensure you import/use the same getIn utility
used elsewhere in the repo and keep references to name, initialValue,
initialStateValue unchanged.

[erikras-richard-agent]

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