Add is_embeddable argument to post types.

src/wp-includes/class-wp-post-type.php

@@ -521,6 +521,7 @@ public function set_props( $args ) {
 			'hierarchical'                    => false,
 			'exclude_from_search'             => null,
 			'publicly_queryable'              => null,
+			'is_embeddable'                   => null,
 			'show_ui'                         => null,
 			'show_in_menu'                    => null,
 			'show_in_nav_menus'               => null,
@@ -565,6 +566,11 @@ public function set_props( $args ) {
 			$args['show_ui'] = $args['public'];
 		}
 
+		// If not set, default to the setting for 'public'.
+		if ( null === $args['is_embeddable'] ) {
+			$args['is_embeddable'] = $args['public'];
+		}
+
 		// If not set, default rest_namespace to wp/v2 if show_in_rest is true.
 		if ( false === $args['rest_namespace'] && ! empty( $args['show_in_rest'] ) ) {
 			$args['rest_namespace'] = 'wp/v2';

src/wp-includes/embed.php

@@ -331,11 +331,12 @@ function wp_oembed_register_route() {
  * Adds oEmbed discovery links in the head element of the website.
  *
  * @since 4.4.0
+ * @since x.x.x Output was adjusted to only embed if the post supports it.
  */
 function wp_oembed_add_discovery_links() {
 	$output = '';
 
-	if ( is_singular() ) {
+	if ( is_singular() && is_post_embeddable() ) {
 		$output .= '<link rel="alternate" type="application/json+oembed" href="' . esc_url( get_oembed_endpoint_url( get_permalink() ) ) . '" />' . "\n";
 
 		if ( class_exists( 'SimpleXMLElement' ) ) {
@@ -538,11 +539,12 @@ function get_post_embed_html( $width, $height, $post = null ) {
  * Retrieves the oEmbed response data for a given post.
  *
  * @since 4.4.0
+ * @since x.x.x Output was adjusted to only embed if the post type supports it.
  *
  * @param WP_Post|int $post  Post ID or post object.
  * @param int         $width The requested width.
- * @return array|false Response data on success, false if post doesn't exist
- *                     or is not publicly viewable.
+ * @return array|false Response data on success, false if post doesn't exist,
+ *                     is not publicly viewable or post type is not embeddable.
  */
 function get_oembed_response_data( $post, $width ) {
 	$post  = get_post( $post );
@@ -556,6 +558,10 @@ function get_oembed_response_data( $post, $width ) {
 		return false;
 	}
 
+	if ( ! is_post_embeddable( $post ) ) {
+		return false;
+	}
+
 	/**
 	 * Filters the allowed minimum and maximum widths for the oEmbed response.
 	 *

src/wp-includes/post.php

@@ -2384,6 +2384,41 @@ function is_post_publicly_viewable( $post = null ) {
 	return is_post_type_viewable( $post_type ) && is_post_status_viewable( $post_status );
 }
 
+/**
+ * Determines whether a post is "embeddable".
+ *
+ * The "is_embeddable" value of the post's type will be evaluated.
+ *
+ * @since x.x.x
+ *
+ * @param int|WP_Post|null $post Optional. Post ID or `WP_Post` object. Defaults to global $post.
+ * @return bool Whether the post should be considered embeddable.
+ */
+function is_post_embeddable( $post = null ) {
+	$post = get_post( $post );
+
+	if ( ! $post ) {
+		return false;
+	}
+
+	$is_embeddable = false;
+
+	$post_type = get_post_type_object( $post->post_type );
+	if ( $post_type ) {
+		$is_embeddable = $post_type->is_embeddable;
+	}
+
+	/**
+	 * Filter whether a post is embeddable.
+	 *
+	 * @since x.x.x
+	 *
+	 * @param bool    $is_embeddable Whether the post is embeddable.
+	 * @param WP_Post $post Post object.
+	 */
+	return apply_filters( 'is_post_embeddable', $is_embeddable, $post );
+}
+
 /**
  * Retrieves an array of the latest posts, or posts matching the given criteria.
  *

tests/phpunit/tests/oembed/discovery.php

@@ -85,4 +85,19 @@ public function test_add_oembed_discovery_links_to_attachment() {
 
 		$this->assertSame( $expected, get_echo( 'wp_oembed_add_discovery_links' ) );
 	}
+
+	/**
+	 * @ticket 35567
+	 */
+	public function test_wp_oembed_add_discovery_links_non_embeddable_post_type_output_should_be_empty() {
+		register_post_type( 'not_embeddable', array( 'is_embeddable' => false ) );
+
+		$post = self::factory()->post->create_and_get(
+			array(
+				'post_type' => 'not_embeddable',
+			)
+		);
+
+		$this->assertFalse( get_oembed_response_data( $post, 100 ) );
+	}
 }

tests/phpunit/tests/oembed/template.php

@@ -345,4 +345,60 @@ public function test_wp_maybe_enqueue_oembed_host_js_without_wp_head_action() {
 		wp_maybe_enqueue_oembed_host_js( $post_embed );
 		$this->assertFalse( $scripts->query( 'wp-embed', 'enqueued' ) );
 	}
+
+	/**
+	 * @ticket 35567
+	 */
+	public function test_is_embeddable_post_non_existent_post() {
+		$this->assertFalse( is_post_embeddable( 0 ) );
+	}
+
+	/**
+	 * @ticket 35567
+	 */
+	public function test_is_embeddable_post_should_return_false_for_non_embeddable_post_type() {
+		register_post_type( 'not_embeddable', array( 'is_embeddable' => false ) );
+
+		$post = self::factory()->post->create_and_get(
+			array(
+				'post_type' => 'not_embeddable',
+			)
+		);
+
+		$this->assertFalse( is_post_embeddable( $post ) );
+	}
+
+	/**
+	 * @ticket 35567
+	 */
+	public function test_is_embeddable_post_should_return_true_for_embeddable_post_type() {
+		register_post_type( 'embeddable', array( 'is_embeddable' => true ) );
+
+		$post = self::factory()->post->create_and_get(
+			array(
+				'post_type' => 'embeddable',
+			)
+		);
+
+		$this->assertTrue( is_post_embeddable( $post ) );
+	}
+
+	/**
+	 * @ticket 35567
+	 */
+	public function test_is_embeddable_post_filtered() {
+		register_post_type( 'not_embeddable', array( 'is_embeddable' => false ) );
+
+		$post = self::factory()->post->create_and_get(
+			array(
+				'post_type' => 'not_embeddable',
+			)
+		);
+
+		add_filter( 'is_post_embeddable', '__return_true' );
+		$embeddable = is_post_embeddable( $post );
+		remove_filter( 'is_post_embeddable', '__return_true' );
+
+		$this->assertTrue( $embeddable );
+	}
 }

tests/phpunit/tests/post/types.php

@@ -589,4 +589,34 @@ public function test_get_post_types_by_support_excluding_features() {
 	public function test_get_post_types_by_support_non_existant_feature() {
 		$this->assertSameSets( array(), get_post_types_by_support( 'somefeature' ) );
 	}
+
+	/**
+	 * @group oembed
+	 * @ticket 35567
+	 */
+	public function test_register_post_type_is_embeddable_defaults_to_public_argument() {
+		$post_type = register_post_type( rand_str( 10 ) );
+		$this->assertFalse( $post_type->is_embeddable );
+
+		$post_type = register_post_type( rand_str( 10 ), array( 'public' => true ) );
+		$this->assertTrue( $post_type->is_embeddable );
+	}
+
+	/**
+	 * @group oembed
+	 * @ticket 35567
+	 */
+	public function test_register_post_type_override_is_embeddable() {
+		$post_type = register_post_type( rand_str( 10 ), array( 'is_embeddable' => true ) );
+		$this->assertTrue( $post_type->is_embeddable );
+
+		$post_type = register_post_type(
+			rand_str( 10 ),
+			array(
+				'public'        => true,
+				'is_embeddable' => false,
+			)
+		);
+		$this->assertFalse( $post_type->is_embeddable );
+	}
 }