Abilities API: add filters for input and output validation

[priethor]

The Abilities API currently validates ability input and output against JSON Schema using WordPress's built-in rest_validate_value_from_schema(), which supports only a subset of JSON Schema Draft 4 (aligning with WordPress core). This approach is reliable for core compatibility but limits extenders to dated JSON Schema features, missing newer ones like $ref references for composability and reusability, and not keyword to exclude patterns.

Developers extending the Abilities API that need more expressive schema validation have no way to override the default validator without forking or monkey-patching.

Proposed Solution

Introduce two hooks to allow custom validation:

/**
 * Filters the input validation result for an ability.
 *
 * @since 7.0.0
 *
 * @param true|WP_Error $is_valid Validation result (true or WP_Error).
 * @param mixed         $input    The input being validated.
 * @param string        $name     The ability name.
 */
apply_filters( 'wp_ability_validate_input', $is_valid, $input, $name );

/**
 * Filters the output validation result for an ability.
 *
 * @since 7.0.0
 *
 * @param true|WP_Error $is_valid Validation result (true or WP_Error).
 * @param mixed         $output   The output being validated.
 * @param string        $name     The ability name.
 */
apply_filters( 'wp_ability_validate_output', $is_valid, $output, $name );

Related

• GitHub Issue: ​https://github.com/WordPress/abilities-api/issues/149
• GitHub PR: ​https://github.com/WordPress/abilities-api/pull/150

Trac ticket: https://core.trac.wordpress.org/ticket/64311