Editor: Preload the view config form request for the DataForm inspector

[jorgefilipecosta]

What?

Preloads /wp/v2/view-config?kind=postType&name=<post_type>&_fields=form in the post editor when the "Editor Inspector: Use DataForm" experiment (gutenberg-dataform-inspector) is enabled, and drives the getViewConfig resolver during the editor kickoff so the preload is actually consumed before React mounts.

Why?

When the experiment is active, DataFormPostSummary requests the entity form config on mount via the getViewConfig resolver. Because the request was not preloaded, the inspector sidebar rendered an empty form first and then flashed once the response arrived.

How?

• lib/compat/wordpress-7.1/preload.php: adds the path in gutenberg_block_editor_preload_paths_7_1() for the core/edit-post context, using the current post type (the client requests name: postType, so pages and custom post types are covered too). The path is only added when the experiment is enabled; otherwise it would never be consumed and would waste page weight.
• packages/edit-post/src/index.js: adds getViewConfig( 'postType', postType, { fields: 'form' } ) to the preloadResolutions() kickoff, gated on window.__experimentalDataFormInspector. The post editor clears the preload cache before React mounts (clearPreloadedData() runs once the kickoff settles), so a preload entry is only useful if a kickoff resolver consumes it. The args match the useViewConfig call in @wordpress/views exactly so the sidebar shares the finished resolution instead of re-requesting.

Notes on the path shape:

• No _locale=user: apiFetch's preloading middleware runs before the user-locale middleware appends that param, so the preload cache is matched against the path without it.
• Query-arg order is irrelevant (both sides are normalized with normalizePath), but the _fields subset must match the resolver request exactly (form).

Automated test

Adds a test to test/e2e/specs/preload/post-editor.spec.js that enables the experiment, opens a post, and asserts that:

1. All preload entries are consumed during kickoff (catches the preload path drifting from the client request).
2. No wp/v2/view-config request reaches the network (catches the preload being dropped, which reintroduces the flash).

Testing Instructions

1. Enable the "Editor Inspector: Use DataForm" experiment in Gutenberg → Experiments.
2. Open a post in the post editor.
3. Observe that the document sidebar summary renders without flashing from an empty form.
4. In the network tab, verify no request to wp/v2/view-config is made (it is served from the preload cache).
5. Disable the experiment and verify the editor still loads correctly and no unused view-config preload appears in the page source.
6. npm run test:e2e -- test/e2e/specs/preload/post-editor.spec.js
7. Verfified the added end to end tests passes.
8. Reverted our non test changes and vierifed the end to end test fails.

[github-actions]

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

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[github-actions]

Size Change: +37 B (0%)

Total Size: 7.67 MB

📦 View Changed

Filename	Size	Change
build/scripts/edit-post/index.min.js	52.2 kB	+37 B (+0.07%)

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[ntsekouras]

The request should match DataFormPostSummary. Noting for updating the comment.

Additionally this code should live under lib/experimental since this experiment won't be part of 7.1.

[jorgefilipecosta]

Hi @ntsekouras your feedback was applied.

[ntsekouras]

Left a super small nit, but this looks good. Thanks!

[ntsekouras]

Nit: no need to return summary here.