Update GET coauthors API endpoint to be public

* Adds `get_authors_with_api_schema` function that returns the co-authors from the WP_REST_Server so the schema and data match the editor.
* Uses that new function in the Co-Authors Block when getting the authors for a post.

php/api/endpoints/class-coauthors-controller.php

@@ -82,7 +82,7 @@ public function register_coauthors_route(): void {
 				array(
 					'methods'             => WP_REST_Server::READABLE,
 					'callback'            => array( $this, 'get_items' ),
-					'permission_callback' => array( $this, 'get_items_permission_check' ),
+					'permission_callback' => '__return_true'
 				),
 			)
 		);
@@ -198,32 +198,6 @@ function( $author ) use ( $request ) : array {
 		);
 	}
 
-	/**
-	 * Get Items Permission Check
-	 *
-	 * @since 3.6.0
-	 * @param WP_REST_Request $request
-	 * @return bool|WP_Error
-	 */
-	public function get_items_permission_check( WP_REST_Request $request ) {
-
-		$post_id = $request->get_param( 'post_id' );
-
-		if ( current_user_can( 'edit_post', $post_id ) ) {
-			return true;
-		}
-
-		if ( is_coauthor_for_post( get_current_user(), $post_id ) ) {
-			return true;
-		}
-
-		return new WP_Error(
-			'rest_cannot_view',
-			__( 'Sorry, you are not allowed to view co-authors of this post.', 'co-authors-plus' ),
-			array( 'status' => rest_authorization_required_code() )
-		);
-	}
-
 	/**
 	 * Retrieves the CoAuthor schema, conforming to JSON Schema.
 	 *

php/blocks/block-coauthors/class-block-coauthors.php

@@ -9,6 +9,7 @@
 namespace CoAuthors\Blocks;
 
 use WP_Block;
+use CoAuthors\Blocks;
 
 /**
  * Block CoAuthors
@@ -96,19 +97,9 @@ public static function render_block( array $attributes, string $content, WP_Bloc
 			return '';
 		}
 
-		$authors = array_values(
-			array_filter(
-				array_map(
-					'CoAuthors\Blocks::get_author_with_api_schema',
-					get_coauthors( $post_id )
-				),
-				function( $author ) : bool {
-					return ! is_null( $author );
-				}
-			)
-		);
+		$authors = Blocks::get_authors_with_api_schema( $post_id );
 
-		if ( ! is_array( $authors ) || empty( $authors ) ) {
+		if ( empty( $authors ) ) {
 			return '';
 		}
 

php/blocks/class-blocks.php

@@ -196,4 +196,39 @@ public static function get_author_with_api_schema( $author ): ?array {
 
 		return $data;
 	}
+
+	/**
+	 * Get CoAuthors with API Schema
+	 * 
+	 * Use the global WP_REST_Server to fetch co-authors for a post,
+	 * so that it matches what a user would see in the editor.
+	 * 
+	 * @since 3.6.0
+	 * @param int   $post_id Post ID for querying co-authors.
+	 * @param array $data Co-authors as returned by the REST API.
+	 */
+	public static function get_authors_with_api_schema( int $post_id ): array {
+
+		$data = rest_get_server()->dispatch(
+			WP_REST_Request::from_url(
+				home_url(
+					sprintf(
+						'/wp-json/coauthors/v1/coauthors?post_id=%d',
+						$post_id
+					)
+				)
+			)
+		)->get_data();
+
+		if ( ! is_array( $data ) ) {
+			return array();
+		}
+
+		// The presence of `code` indicates this is an error response.
+		if ( array_key_exists( 'code', $data ) ) {
+			return array();
+		}
+
+		return $data;
+	}
 }