ComboboxControl: narrow onChange callback type to string | null

[oandregal]

Follow up to this comment.

What?

Narrows the ComboboxControl onChange callback parameter type from string | null | undefined to string | null by hoisting the value type into a named alias, and reverts the undefined widening that #81449 added to the DataForm combobox handler.

Why?

The onChange parameter was typed via an indexed access on the optional value prop:

type ComboboxControlProps = {
	value?: string | null;
	onChange?: ( value: CaseOne[ 'value' ] ) => void;
};

And so ComboboxControlProps[ 'value' ] (due to the ? modifier on value) leaks undefined into the onChange callback parameter type. The component never actually calls onChange with undefined — only with a suggestion string or null on reset — so consumers were forced to widen their handlers for a value that never arrives (as happened in #81449).

How?

By hoisting and sharing the type:

type ComboboxControlValue = string | null;
type ComboboxControlProps = {
	value?: ComboboxControlValue;
	onChange?: ( value: ComboboxControlValue ) => void;
};

Checked the impact on major consumers and there were no handler breaks.

Testing Instructions

1. Run npm run build (or a TypeScript check) and confirm it passes.
2. In packages/dataviews/src/components/dataform-controls/combobox.tsx, confirm the onChange handler typed ( newValue: string | null ) compiles without the previous | undefined widening.

Use of AI Tools

Authored with the assistance of Claude Code (implementation, consumer-impact analysis, and this description); reviewed and verified by me.

[github-actions]

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Co-authored-by: oandregal <oandregal@git.wordpress.org>
Co-authored-by: jorgefilipecosta <jorgefilipecosta@git.wordpress.org>
Co-authored-by: mcsf <mcsf@git.wordpress.org>

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[Copilot]

Pull request overview

Narrows ComboboxControl’s callback type to match its runtime contract and updates affected consumers.

Changes:

• Introduces a shared string | null value type.
• Narrows three consumer handlers.
• Updates package changelogs.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 1 comment.

Show a summary per file

File	Description
packages/components/src/combobox-control/types.ts	Narrows the callback type.
packages/components/CHANGELOG.md	Records the type change.
packages/dataviews/src/components/dataform-controls/combobox.tsx	Narrows the DataForm handler.
packages/dataviews/CHANGELOG.md	Records the internal update.
packages/fields/src/fields/parent/parent-edit.tsx	Narrows the parent handler.
packages/fields/CHANGELOG.md	Records the internal update.
packages/media-fields/src/attached_to/edit.tsx	Narrows the attachment handler.
packages/media-fields/CHANGELOG.md	Records the internal update.

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[oandregal]

46e3ed4

[github-actions]

Size Change: 0 B

Total Size: 7.72 MB

_{compressed-size-action}

[oandregal]

The undefined type was even documented as something we supported.

[jorgefilipecosta]

LGTM 👍

[mcsf]

Glad my suggestion was helpful. :)

[github-actions]

Flaky tests detected in f201100.
Some tests passed with failed attempts. The failures may not be related to this commit but are still reported for visibility. See the documentation for more information.

🔍 Workflow run URL: https://github.com/WordPress/gutenberg/actions/runs/31780731026
📝 Reported tests:

Should navigate inner blocks with arrow keys in /test/e2e/specs/editor/various/writing-flow.spec.js, passed after 1 failed attempt.

TimeoutError: locator.click: Timeout 10000ms exceeded.
Call log:
  - waiting for getByRole('listbox', { name: 'Blocks' }).getByRole('option', { name: 'Paragraph' })

    at WritingFlowUtils.addDemoContent (/home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/various/writing-flow.spec.js:1482:5)
    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/various/writing-flow.spec.js:30:3

adds and activates a new tab when pressing Enter at the end of a tab label in /test/e2e/specs/editor/blocks/tabs.spec.js, passed after 1 failed attempt.

Error: expect(locator).toHaveCount(expected) failed

Locator:  locator('[name="editor-canvas"]').contentFrame().getByRole('tab')
Expected: 3
Received: 2
Timeout:  5000ms

Call log:
  - Expect "toHaveCount" with timeout 5000ms
  - waiting for locator('[name="editor-canvas"]').contentFrame().getByRole('tab')
    14 × locator resolved to 2 elements
       - unexpected value "2"

    at /home/runner/work/gutenberg/gutenberg/test/e2e/specs/editor/blocks/tabs.spec.js:146:25