Knowledge: Introduce the wp_knowledge custom post type

src/wp-includes/capabilities.php

@@ -1365,6 +1365,87 @@ function wp_maybe_grant_site_health_caps( $allcaps, $caps, $args, $user ) {
 	return $allcaps;
 }
 
+/**
+ * Filters the user capabilities to grant the `wp_knowledge` post type capabilities as necessary.
+ *
+ * The `wp_knowledge` post type uses a `knowledge`-prefixed capability set that is
+ * granted dynamically rather than stored on roles. Administrators (users with
+ * `manage_options`) receive every knowledge capability. Contributors, authors,
+ * and editors (users with `edit_posts`) may list and create knowledge rows and
+ * fully manage their own private rows; publishing knowledge and acting on other
+ * users' rows is reserved for administrators. Subscribers receive nothing and
+ * are stopped at the post-type door by the `read_knowledge` mapping.
+ *
+ * @since 7.1.0
+ *
+ * @param bool[]   $allcaps An array of all the user's capabilities.
+ * @param string[] $caps    Required primitive capabilities for the requested capability.
+ * @param array    $args {
+ *     Arguments that accompany the requested capability check.
+ *
+ *     @type string    $0 Requested capability.
+ *     @type int       $1 Concerned user ID.
+ *     @type mixed  ...$2 Optional second and further parameters, typically object ID.
+ * }
+ * @param WP_User  $user    The user object.
+ * @return bool[] Filtered array of the user's capabilities.
+ */
+function wp_maybe_grant_knowledge_caps( array $allcaps, array $caps, array $args, WP_User $user ): array {
+	if ( ! empty( $allcaps['manage_options'] ) ) {
+		$allcaps['read_knowledge']             = true;
+		$allcaps['edit_knowledge']             = true;
+		$allcaps['edit_others_knowledge']      = true;
+		$allcaps['edit_published_knowledge']   = true;
+		$allcaps['edit_private_knowledge']     = true;
+		$allcaps['publish_knowledge']          = true;
+		$allcaps['delete_knowledge']           = true;
+		$allcaps['delete_others_knowledge']    = true;
+		$allcaps['delete_published_knowledge'] = true;
+		$allcaps['delete_private_knowledge']   = true;
+		$allcaps['read_private_knowledge']     = true;
+
+		return $allcaps;
+	}
+
+	if ( empty( $allcaps['edit_posts'] ) ) {
+		return $allcaps;
+	}
+
+	/*
+	 * Ambient floor for contributors and above: `read_knowledge` clears the
+	 * post-type read check; `edit_knowledge` clears the create and ownership
+	 * checks that do not pass a post ID. Per-post primitives are granted only
+	 * in the per-post branch below.
+	 */
+	$allcaps['read_knowledge'] = true;
+	$allcaps['edit_knowledge'] = true;
+
+	if ( ! isset( $args[0], $args[2] ) ) {
+		return $allcaps;
+	}
+
+	if ( ! in_array( $args[0], array( 'edit_post', 'delete_post', 'read_post' ), true ) ) {
+		return $allcaps;
+	}
+
+	$post = get_post( $args[2] );
+	if (
+		! $post instanceof WP_Post ||
+		'wp_knowledge' !== $post->post_type ||
+		(int) $post->post_author !== (int) $user->ID ||
+		'private' !== $post->post_status
+	) {
+		return $allcaps;
+	}
+
+	$allcaps['edit_private_knowledge']   = true;
+	$allcaps['delete_knowledge']         = true;
+	$allcaps['delete_private_knowledge'] = true;
+	$allcaps['read_private_knowledge']   = true;
+
+	return $allcaps;
+}
+
 return;
 
 // Dummy gettext calls to get strings in the catalog.

src/wp-includes/default-filters.php

@@ -773,6 +773,7 @@
 add_filter( 'user_has_cap', 'wp_maybe_grant_install_languages_cap', 1 );
 add_filter( 'user_has_cap', 'wp_maybe_grant_resume_extensions_caps', 1 );
 add_filter( 'user_has_cap', 'wp_maybe_grant_site_health_caps', 1, 4 );
+add_filter( 'user_has_cap', 'wp_maybe_grant_knowledge_caps', 1, 4 );
 
 // Block templates post type and rendering.
 add_filter( 'render_block_context', '_block_template_render_without_post_block_context' );
@@ -786,6 +787,10 @@
 // wp_navigation post type.
 add_filter( 'rest_wp_navigation_item_schema', array( 'WP_Navigation_Fallback', 'update_wp_navigation_post_schema' ) );
 
+// wp_knowledge post type.
+add_action( 'save_post_wp_knowledge', '_wp_knowledge_ensure_default_type_term' );
+add_filter( 'wp_insert_term_data', '_wp_knowledge_maybe_map_term_label', 10, 2 );
+
 // Fluid typography.
 add_filter( 'render_block', 'wp_render_typography_support', 10, 2 );
 

src/wp-includes/knowledge.php

@@ -0,0 +1,142 @@
+<?php
+/**
+ * Knowledge API: Public functions for the `wp_knowledge` post type.
+ *
+ * The Knowledge post type is a private-by-default storage primitive. Individual
+ * rows are classified by one or more terms in the `wp_knowledge_type` taxonomy
+ * (for example "guideline", "memory", or "note"). This file holds the type
+ * registry, the default-term fallback applied on save, and the helper that
+ * gives lazily created type terms a human-readable label.
+ *
+ * @package WordPress
+ * @subpackage Knowledge
+ * @since 7.1.0
+ */
+
+/**
+ * Retrieves the registered knowledge types, keyed by slug.
+ *
+ * Plugins can register their own types via the {@see 'wp_knowledge_types'} filter.
+ *
+ * @since 7.1.0
+ *
+ * @return array {
+ *     Slug-keyed map of knowledge types.
+ *
+ *     @type array ...$0 {
+ *         Data for a single knowledge type.
+ *
+ *         @type string $title The human-readable label for the type.
+ *     }
+ * }
+ * @phpstan-return array<non-empty-string, array{title: non-empty-string}>
+ */
+function wp_knowledge_types(): array {
+	/**
+	 * Filters the knowledge types available on this site.
+	 *
+	 * @since 7.1.0
+	 *
+	 * @param array $types {
+	 *     Slug-keyed map of knowledge types.
+	 *
+	 *     @type array ...$0 {
+	 *         Data for a single knowledge type.
+	 *
+	 *         @type string $title The human-readable label for the type.
+	 *     }
+	 * }
+	 * @phpstan-param array<non-empty-string, array{title: non-empty-string}> $types
+	 */
+	return apply_filters(
+		'wp_knowledge_types',
+		array(
+			'guideline' => array(
+				'title' => _x( 'Guideline', 'knowledge type' ),
+			),
+			'memory'    => array(
+				'title' => _x( 'Memory', 'knowledge type' ),
+			),
+			'note'      => array(
+				'title' => _x( 'Note', 'knowledge type' ),
+			),
+		)
+	);
+}
+
+/**
+ * Assigns the `note` fallback term when a knowledge post is saved without a type.
+ *
+ * Hooked to the `save_post_wp_knowledge` action so that every knowledge row has
+ * at least one `wp_knowledge_type` term. Uses get_the_terms() so the check is
+ * served by the object term cache.
+ *
+ * @since 7.1.0
+ * @access private
+ *
+ * @param int $post_id Saved post ID.
+ */
+function _wp_knowledge_ensure_default_type_term( int $post_id ): void {
+	if ( wp_is_post_revision( $post_id ) ) {
+		return;
+	}
+
+	$terms = get_the_terms( $post_id, 'wp_knowledge_type' );
+	if ( is_wp_error( $terms ) || ! empty( $terms ) ) {
+		return;
+	}
+
+	/*
+	 * Resolve to a term ID up front, creating the term on first use:
+	 * wp_set_object_terms() interprets strings as names for hierarchical
+	 * taxonomies, not slugs.
+	 */
+	$term = term_exists( 'note', 'wp_knowledge_type' );
+	if ( ! $term ) {
+		$term = wp_insert_term( 'note', 'wp_knowledge_type' );
+		if ( is_wp_error( $term ) ) {
+			return;
+		}
+	}
+
+	wp_set_object_terms( $post_id, (int) $term['term_id'], 'wp_knowledge_type' );
+}
+
+/**
+ * Swaps a raw knowledge-type slug for its registered label on term creation.
+ *
+ * Hooked to the `wp_insert_term_data` filter. When wp_set_object_terms() is
+ * called with a slug that does not yet exist, wp_insert_term() fires and this
+ * filter runs after WordPress has computed both `name` and `slug`. A `name`
+ * equal to `slug` indicates the term was created from a raw slug (for example by
+ * wp_set_object_terms()) rather than from a user-provided label, so the label is
+ * replaced with the title from wp_knowledge_types(). Because term names are
+ * persisted in the database, the translated title is stored in the locale active
+ * when the term is created.
+ *
+ * @since 7.1.0
+ * @access private
+ *
+ * @param array  $data     Term data to be inserted (keyed by column name).
+ * @param string $taxonomy Taxonomy slug.
+ * @return array Possibly modified term data.
+ *
+ * @phpstan-param  array<non-empty-string, mixed> $data
+ * @phpstan-return array<non-empty-string, mixed>
+ */
+function _wp_knowledge_maybe_map_term_label( array $data, string $taxonomy ): array {
+	if ( 'wp_knowledge_type' !== $taxonomy ) {
+		return $data;
+	}
+
+	if ( $data['name'] !== $data['slug'] ) {
+		return $data;
+	}
+
+	$types = wp_knowledge_types();
+	if ( isset( $types[ $data['slug'] ] ) ) {
+		$data['name'] = $types[ $data['slug'] ]['title'];
+	}
+
+	return $data;
+}

src/wp-includes/post.php

@@ -16,6 +16,7 @@
  * See {@see 'init'}.
  *
  * @since 2.9.0
+ * @since 7.1.0 Added the `wp_knowledge` post type.
  */
 function create_initial_post_types() {
 	WP_Post_Type::reset_default_labels();
@@ -657,6 +658,55 @@ function create_initial_post_types() {
 		)
 	);
 
+	register_post_type(
+		'wp_knowledge',
+		array(
+			'labels'                => array(
+				'name'          => _x( 'Knowledge', 'post type general name' ),
+				'singular_name' => _x( 'Knowledge Item', 'post type singular name' ),
+			),
+			'public'                => false,
+			'_builtin'              => true, /* internal use only. don't use this when registering your own post type. */
+			'hierarchical'          => false,
+			/*
+			 * Knowledge rows have no native post-type screens; they are managed
+			 * through the REST API and consuming features, not the wp-admin UI.
+			 */
+			'show_ui'               => false,
+			'map_meta_cap'          => true,
+			/*
+			 * "Knowledge" is a mass noun, so the singular and plural capability
+			 * bases must differ: with both set to `knowledge`, the generated
+			 * per-post meta caps (`edit_knowledge_item`) would collide with the
+			 * primitive caps (`edit_knowledge`). The `*_knowledge_item` forms are
+			 * never granted directly; `map_meta_cap()` resolves them onto the
+			 * primitives, which `wp_maybe_grant_knowledge_caps()` synthesizes.
+			 */
+			'capability_type'       => array( 'knowledge_item', 'knowledge' ),
+			/*
+			 * `read` is remapped so that subscribers (who hold the base `read`
+			 * capability) are stopped at the post-type door. Every other
+			 * primitive defaults to a `knowledge`-prefixed capability granted by
+			 * `wp_maybe_grant_knowledge_caps()`.
+			 */
+			'capabilities'          => array(
+				'read' => 'read_knowledge',
+			),
+			'query_var'             => false,
+			'rewrite'               => false,
+			'show_in_rest'          => true,
+			'rest_base'             => 'knowledge',
+			'rest_controller_class' => 'WP_REST_Knowledge_Controller',
+			'supports'              => array( 'title', 'editor', 'excerpt', 'author', 'revisions' ),
+		)
+	);
+	/*
+	 * Disable autosave endpoints for knowledge. 'editor' support implies
+	 * 'autosave', but knowledge is headless storage with no editor session, so
+	 * the autosave REST routes have no consumer. Revision history is retained.
+	 */
+	remove_post_type_support( 'wp_knowledge', 'autosave' );
+
 	register_post_status(
 		'publish',
 		array(