REST API: Allow-list ability schema response keywords

[gziolo]

What?

This hardens the Ability REST API schema response preparation by switching from an internal-keyword deny-list to a schema-keyword allow-list.

Ability input and output schemas exposed through REST responses now keep only:

• keywords returned by rest_get_allowed_schema_keywords();
• a small local set of additional draft-04 schema keywords that clients may use for validation or schema traversal.

This continues to preserve nested schema structures while stripping WordPress-internal keys such as sanitize_callback, validate_callback, and arg_options, along with other unsupported schema keywords such as example, examples, context, and readonly.

Why?

The previous implementation stripped only known internal keywords. An allow-list is stricter and better aligned with the REST API schema surface: unknown or unsupported schema keywords are not exposed to REST clients by default.

The local additional keyword list intentionally preserves a few draft-04 keywords that are useful to stricter client-side validators. This aligns with the approach documented in WordPress/gutenberg#78783, which adds tests for the strict JSON Schema keyword surface supported by the client-side abilities validator.

At the moment, the Core and Gutenberg changes aim to mirror the same allowed schema-property surface: unknown schema keywords should be skipped or stripped rather than passed through. Based on review feedback, we can also move in the opposite direction by relaxing the client-side validator to ignore unknown schema properties instead of treating them as unsupported. In practice, the two possible endpoints are either a strict shared allow-list or a relaxed client that skips unknown properties.

Test Coverage

This PR now mirrors the WordPress-specific keyword cases covered in WordPress/gutenberg#78783 by documenting that unsupported schema keywords are stripped from both ability input_schema properties and top-level output_schema definitions:

• sanitize_callback
• validate_callback
• arg_options
• example
• examples
• context
• readonly

It also verifies that valid draft-04 required arrays are preserved. Boolean required handling is intentionally left for a follow-up PR.

Related

• https://core.trac.wordpress.org/ticket/64955
• Abilities: Add validation tests pinning behavior for WP-specific schema keywords gutenberg#78783

Testing

• php -l tests/phpunit/tests/rest-api/wpRestAbilitiesV1ListController.php
• git diff --check -- tests/phpunit/tests/rest-api/wpRestAbilitiesV1ListController.php

Attempted after the latest test-only update, but the local Docker runner hung after creating the PHPUnit container:

• npm run test:php -- --filter Tests_REST_API_WpRestAbilitiesV1ListController

Previously run on this branch before the latest test-only update:

• php -l src/wp-includes/rest-api/endpoints/class-wp-rest-abilities-v1-list-controller.php
• npm run typecheck:php -- src/wp-includes/rest-api/endpoints/class-wp-rest-abilities-v1-list-controller.php --no-progress

[github-actions]

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[github-actions]

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Props gziolo, jorgefilipecosta.

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[jorgefilipecosta]

Left some comments for consideration but the changes look good 👍

[gziolo]

A commit was made that references the Trac ticket included in the description of this pull request.

SVN changeset: 62447
GitHub commit: da7588b

This PR will be closed, but please confirm the accuracy of this and reopen if there is more work to be done.