Add Block recursion error reporting (WordPress#26923)

lib/block-recursion-error.php

@@ -0,0 +1,27 @@
+<?php
+/**
+ * Blocks API: Block recursion error handling.
+ *
+ * @package gutenberg
+ */
+
+/**
+ * Reports a recursion error to the user.
+ *
+ * If WP_DEBUG is true then additional information is displayed.
+ * Use the $class parameter to override default behavior.
+ *
+ * @param $id string|integer recursive ID detected
+ * @param $type string content type
+ * @return string HTML reporting the error to the user
+ */
+function gutenberg_report_recursion_error( $message=null, $class=null ) {
+	$recursion_control = WP_Block_Recursion_Control::get_instance();
+	if ( $class && class_exists( $class ) ) {
+		$recursion_error = new $class( $recursion_control );
+	} else {
+		$recursion_error = new WP_Block_Recursion_Error( $recursion_control );
+	}
+	$html = $recursion_error->report_recursion_error( $message );
+	return $html;
+}

lib/class-wp-block-recursion-error.php

@@ -0,0 +1,139 @@
+<?php
+/**
+ * Blocks API: WP_Block_Recursion_Error class
+ *
+ * @package Gutenberg
+ */
+
+/**
+ * Implements the recursion error functions in an extendable class.
+ * The extending class may be specified as the $class parameter.
+ *
+ * ```
+ * $html = gutenberg_report_recursion_error( $message, $class=null )
+ * ```
+ */
+class WP_Block_Recursion_Error {
+
+	private $recursion_control = null;
+	protected $bad_id = null;
+	protected $bad_processed_content = [];
+	protected $block_name = null; // The block name
+	protected $message = null;
+
+	public function __construct( $recursion_control = null ) {
+		if ( $recursion_control ) {
+			$this->recursion_control = $recursion_control;
+		} else {
+			$this->recursion_control = WP_Block_Recursion_Control::get_instance();
+		}
+	}
+
+	/**
+	 * Start to produce the error block to be displayed on the front end.
+	 *
+	 * @TODO Implement as a core message block, when available.
+	 *
+	 * @return string
+	 */
+	function start_error_block() {
+		$content = '<div class="recursion-error">';
+		return $content;
+	}
+
+	/**
+	 * Complete the error block to be displayed on the front end.
+	 *
+	 * @TODO Implement as a core message block, when available.
+	 *
+	 * @return string
+	 */
+	function complete_error_block() {
+		$content = '</div>';
+		return $content;
+	}
+
+	/**
+	 * Returns the message.
+	 *
+	 * The default message varies depending on the block type where recursion was detected.
+	 *
+	 * @return string
+	 */
+	function get_message() 	{
+		if ( !$this->message ) {
+			switch ($this->block_name) {
+				case 'core/post-content':
+					$this->message = __('Content not available; already processed.', 'gutenberg');
+					break;
+				case 'core/template-part':
+					$this->message = __('Template part not processed to avoid infinite recursion', 'gutenberg');
+					break;
+				case 'core/block':
+					$this->message = __('Reusable block not processed to avoid infinite recursion', 'gutenberg');
+					break;
+				default:
+					$this->message = __('Infinite recursion error prevented', 'gutenberg');
+					$this->message .= sprintf(__('Block name: %1$s', 'gutenberg'), $this->block_name);
+			}
+		}
+		return $this->message;
+	}
+
+	/**
+	 * Returns details to help with problem determination.
+	 *
+	 * This is only done when WP_DEBUG is true.
+	 *
+	 * @TODO Also check if the user is logged in.
+	 * @TODO Also check the user's capability with regards to fixing the problem.
+	 *
+	 * @return string HTML with additional details.
+	 */
+	function report_debug_details() {
+		$content = [];
+		if (defined('WP_DEBUG') && WP_DEBUG) {
+			$content[] = "<span class=\"recursion-error-context \">";
+			$content[] = '<br />';
+			$content[] = sprintf( __( 'Block unique ID: %1$s', 'gutenberg' ), $this->bad_id );
+			$content[] = '<br />';
+			$content[] = sprintf( __( 'Block name: %1$s', 'gutenberg' ), $this->block_name );
+			$content[] = '<br />';
+			$content[] = sprintf( __('Stack: %1$s', 'gutenberg'), implode(',', $this->bad_processed_content) );
+			$content[] = '</span>';
+		}
+		$content = implode(" \n", $content);
+		return $content;
+	}
+
+	/**
+	 * Reports a recursion error to the user.
+	 *
+	 * If WP_DEBUG is true then additional information is displayed.
+	 *
+	 * @param $message string
+	 * @return string
+	 */
+	public function report_recursion_error( $message = null ) {
+		$this->bad_id = $this->recursion_control->get_id();
+		$this->block_name = $this->recursion_control->get_block_name();
+		$this->bad_processed_content = $this->recursion_control->get_processed_content();
+		$this->set_message( $message );
+		$content = $this->start_error_block();
+		$content .= $this->get_message();
+		$content .= $this->report_debug_details();
+		$content .= $this->complete_error_block();
+		return $content;
+	}
+
+	/**
+	 * Sets the message to be displayed.
+	 *
+	 * Note: If the message is null then a default message is displayed.
+	 *
+	 * @param null $message
+	 */
+	public function set_message( $message=null ) {
+		$this->message = $message;
+	}
+}

lib/load.php

@@ -132,3 +132,7 @@ function gutenberg_is_experiment_enabled( $name ) {
 	require_once __DIR__ . '/class-wp-block-recursion-control.php';
 }
 require_once __DIR__ . '/block-recursion-control.php';
+if ( !class_exists( 'WP_Block_Recursion_Error') ) {
+	require_once __DIR__ . '/class-wp-block-recursion-error.php';
+}
+require_once __DIR__ . '/block-recursion-error.php';