Catch WSODs and provide a means for recovery for end users

src/wp-admin/css/list-tables.css

@@ -1301,6 +1301,31 @@ ul.cat-checklist {
 	text-decoration: underline;
 }
 
+.plugins tr.paused th.check-column {
+	border-left: 4px solid #d54e21;
+}
+
+.plugins tr.paused th,
+.plugins tr.paused td {
+	background-color: #fef7f1;
+}
+
+.plugins tr.paused .plugin-title,
+.plugins .paused .dashicons-warning {
+	color: #dc3232;
+}
+
+.plugins .paused .error-display p,
+.plugins .paused .error-display code {
+	font-size: 90%;
+	font-style: italic;
+	color: rgb( 0, 0, 0, 0.7 );
+}
+
+.plugins .resume-link {
+	color: #dc3232;
+}
+
 .plugin-card .update-now:before {
 	color: #f56e28;
 	content: "\f463";

src/wp-admin/includes/admin-filters.php

@@ -121,6 +121,7 @@
 add_action( 'load-themes.php', 'wp_theme_update_rows', 20 ); // After wp_update_themes() is called.
 
 add_action( 'admin_notices', 'update_nag', 3 );
+add_action( 'admin_notices', 'paused_plugins_notice', 5 );
 add_action( 'admin_notices', 'maintenance_nag', 10 );
 
 add_filter( 'update_footer', 'core_update_footer' );

src/wp-admin/includes/class-wp-plugins-list-table.php

@@ -40,7 +40,7 @@ public function __construct( $args = array() ) {
 		);
 
 		$status = 'all';
-		if ( isset( $_REQUEST['plugin_status'] ) && in_array( $_REQUEST['plugin_status'], array( 'active', 'inactive', 'recently_activated', 'upgrade', 'mustuse', 'dropins', 'search' ) ) ) {
+		if ( isset( $_REQUEST['plugin_status'] ) && in_array( $_REQUEST['plugin_status'], array( 'active', 'inactive', 'recently_activated', 'upgrade', 'mustuse', 'dropins', 'search', 'paused' ) ) ) {
 			$status = $_REQUEST['plugin_status'];
 		}
 
@@ -99,6 +99,7 @@ public function prepare_items() {
 			'upgrade'            => array(),
 			'mustuse'            => array(),
 			'dropins'            => array(),
+			'paused'             => array(),
 		);
 
 		$screen = $this->screen;
@@ -209,6 +210,9 @@ public function prepare_items() {
 				if ( $show_network_active ) {
 					// On the non-network screen, show network-active plugins if allowed
 					$plugins['active'][ $plugin_file ] = $plugin_data;
+					if ( is_plugin_paused( $plugin_file ) ) {
+						$plugins['paused'][ $plugin_file ] = $plugin_data;
+					}
 				} else {
 					// On the non-network screen, filter out network-active plugins
 					unset( $plugins['all'][ $plugin_file ] );
@@ -218,6 +222,9 @@ public function prepare_items() {
 				// On the non-network screen, populate the active list with plugins that are individually activated
 				// On the network-admin screen, populate the active list with plugins that are network activated
 				$plugins['active'][ $plugin_file ] = $plugin_data;
+				if ( is_plugin_paused( $plugin_file ) ) {
+					$plugins['paused'][ $plugin_file ] = $plugin_data;
+				}
 			} else {
 				if ( isset( $recently_activated[ $plugin_file ] ) ) {
 					// Populate the recently activated list with plugins that have been recently activated
@@ -436,6 +443,9 @@ protected function get_views() {
 				case 'dropins':
 					$text = _n( 'Drop-ins <span class="count">(%s)</span>', 'Drop-ins <span class="count">(%s)</span>', $count );
 					break;
+				case 'paused':
+					$text = _n( 'Paused <span class="count">(%s)</span>', 'Paused <span class="count">(%s)</span>', $count );
+					break;
 				case 'upgrade':
 					$text = _n( 'Update Available <span class="count">(%s)</span>', 'Update Available <span class="count">(%s)</span>', $count );
 					break;
@@ -647,6 +657,10 @@ public function single_row( $item ) {
 						/* translators: %s: plugin name */
 						$actions['deactivate'] = '<a href="' . wp_nonce_url( 'plugins.php?action=deactivate&amp;plugin=' . urlencode( $plugin_file ) . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'deactivate-plugin_' . $plugin_file ) . '" aria-label="' . esc_attr( sprintf( _x( 'Deactivate %s', 'plugin' ), $plugin_data['Name'] ) ) . '">' . __( 'Deactivate' ) . '</a>';
 					}
+					if ( current_user_can( 'resume_plugin' ) && is_plugin_paused( $plugin_file ) ) {
+						/* translators: %s: plugin name */
+						$actions['resume'] = '<a class="resume-link" href="' . wp_nonce_url( 'plugins.php?action=resume&amp;plugin=' . urlencode( $plugin_file ) . '&amp;plugin_status=' . $context . '&amp;paged=' . $page . '&amp;s=' . $s, 'resume-plugin_' . $plugin_file ) . '" aria-label="' . esc_attr( sprintf( _x( 'Resume execution of %s', 'plugin' ), $plugin_data['Name'] ) ) . '">' . __( 'Resume execution' ) . '</a>';
+					}
 				} else {
 					if ( current_user_can( 'activate_plugin', $plugin_file ) ) {
 						/* translators: %s: plugin name */
@@ -753,6 +767,11 @@ public function single_row( $item ) {
 			$class .= ' update';
 		}
 
+		$paused = is_plugin_paused( $plugin_file );
+		if ( $paused ) {
+			$class .= ' paused';
+		}
+
 		$plugin_slug = isset( $plugin_data['slug'] ) ? $plugin_data['slug'] : sanitize_title( $plugin_name );
 		printf(
 			'<tr class="%s" data-slug="%s" data-plugin="%s">',
@@ -831,12 +850,48 @@ public function single_row( $item ) {
 					 * @param array    $plugin_data An array of plugin data.
 					 * @param string   $status      Status of the plugin. Defaults are 'All', 'Active',
 					 *                              'Inactive', 'Recently Activated', 'Upgrade', 'Must-Use',
-					 *                              'Drop-ins', 'Search'.
+					 *                              'Drop-ins', 'Search', 'Paused'
 					 */
 					$plugin_meta = apply_filters( 'plugin_row_meta', $plugin_meta, $plugin_file, $plugin_data, $status );
 					echo implode( ' | ', $plugin_meta );
 
-					echo '</div></td>';
+					echo '</div>';
+
+					if ( $paused ) {
+						echo sprintf(
+							'<p><span class="dashicons dashicons-warning"></span> <strong>%s</strong></p>',
+							__( 'This plugin failed to load properly and was paused within the admin backend.' )
+						);
+
+						$error = wp_get_plugin_error( $plugin_file );
+
+						if ( false !== $error ) {
+							$constants = get_defined_constants( true );
+							$constants = isset( $constants['Core'] ) ? $constants['Core'] : $constants['internal'];
+
+							foreach ( $constants as $constant => $value ) {
+								if ( 0 === strpos( $constant, 'E_' ) ) {
+									$core_errors[ $value ] = $constant;
+								}
+							}
+
+							$error['type'] = $core_errors[ $error['type'] ];
+
+							echo sprintf(
+								'<div class="error-display"><p>%s</p></div>',
+								sprintf(
+									__( 'The plugin caused an error of type %1$s in line %2$s of the file %3$s. Error message: %4$s' ),
+									"<code>{$error['type']}</code>",
+									"<code>{$error['line']}</code>",
+									"<code>{$error['file']}</code>",
+									"<code>{$error['message']}</code>"
+								)
+							);
+						}
+					}
+
+
+					echo '</td>';
 					break;
 				default:
 					$classes = "$column_name column-$column_name $class";
@@ -869,7 +924,7 @@ public function single_row( $item ) {
 		 * @param array  $plugin_data An array of plugin data.
 		 * @param string $status      Status of the plugin. Defaults are 'All', 'Active',
 		 *                            'Inactive', 'Recently Activated', 'Upgrade', 'Must-Use',
-		 *                            'Drop-ins', 'Search'.
+		 *                            'Drop-ins', 'Search', 'Paused'.
 		 */
 		do_action( 'after_plugin_row', $plugin_file, $plugin_data, $status );
 
@@ -885,7 +940,7 @@ public function single_row( $item ) {
 		 * @param array  $plugin_data An array of plugin data.
 		 * @param string $status      Status of the plugin. Defaults are 'All', 'Active',
 		 *                            'Inactive', 'Recently Activated', 'Upgrade', 'Must-Use',
-		 *                            'Drop-ins', 'Search'.
+		 *                            'Drop-ins', 'Search', 'Paused'
 		 */
 		do_action( "after_plugin_row_{$plugin_file}", $plugin_file, $plugin_data, $status );
 	}

src/wp-admin/includes/plugin.php

@@ -444,6 +444,8 @@ function _get_dropins() {
 		'install.php'        => array( __( 'Custom installation script.' ), true ), // auto on installation
 		'maintenance.php'    => array( __( 'Custom maintenance message.' ), true ), // auto on maintenance
 		'object-cache.php'   => array( __( 'External object cache.' ), true ), // auto on load
+		'php-error.php'      => array( __( 'Custom PHP error message.' ), true ), // auto on error
+		'shutdown-handler'   => array( __( 'Custom PHP shutdown handler.' ), true ), // auto on error
 	);
 
 	if ( is_multisite() ) {
@@ -496,6 +498,57 @@ function is_plugin_inactive( $plugin ) {
 	return ! is_plugin_active( $plugin );
 }
 
+/**
+ * Determines whether a plugin is technically active but was paused while
+ * loading.
+ *
+ * For more information on this and similar theme functions, check out
+ * the {@link https://developer.wordpress.org/themes/basics/conditional-tags/
+ * Conditional Tags} article in the Theme Developer Handbook.
+ *
+ * @since 5.0.0
+ *
+ * @param string $plugin Path to the plugin file relative to the plugins directory.
+ * @return bool True, if in the active plugins list. False, not in the list.
+ */
+function is_plugin_paused( $plugin ) {
+	if ( ! isset( $GLOBALS['_paused_plugins'] ) ) {
+		return false;
+	}
+
+	if ( ! is_plugin_active( $plugin ) || is_plugin_active_for_network( $plugin ) ) {
+		return false;
+	}
+
+	list( $plugin ) = explode( '/', $plugin );
+
+	return array_key_exists( $plugin, $GLOBALS['_paused_plugins'] );
+}
+
+/**
+ * Gets the error that was recorded for a paused plugin.
+ *
+ * @since 5.0.0
+ *
+ * @param string $plugin Path to the plugin file relative to the plugins
+ *                       directory.
+ * @return array|false Array of error information as it was returned by
+ *                     `error_get_last()`, or false if none was recorded.
+ */
+function wp_get_plugin_error( $plugin ) {
+	if ( ! isset( $GLOBALS['_paused_plugins'] ) ) {
+		return false;
+	}
+
+	list( $plugin ) = explode( '/', $plugin );
+
+	if ( ! array_key_exists( $plugin, $GLOBALS['_paused_plugins'] ) ) {
+		return false;
+	}
+
+	return $GLOBALS['_paused_plugins'][ $plugin ];
+}
+
 /**
  * Determines whether the plugin is active for the entire network.
  *
@@ -693,6 +746,11 @@ function deactivate_plugins( $plugins, $silent = false, $network_wide = null ) {
 			continue;
 		}
 
+		// Clean up the database before deactivating the plugin.
+		if ( is_plugin_paused( $plugin ) ) {
+			resume_plugin( $plugin );
+		}
+
 		$network_deactivating = false !== $network_wide && is_plugin_active_for_network( $plugin );
 
 		if ( ! $silent ) {
@@ -887,6 +945,11 @@ function delete_plugins( $plugins, $deprecated = '' ) {
 			uninstall_plugin( $plugin_file );
 		}
 
+		// Clean up the database before removing the plugin.
+		if ( is_plugin_paused( $plugin_file ) ) {
+			resume_plugin( $plugin_file );
+		}
+
 		/**
 		 * Fires immediately before a plugin deletion attempt.
 		 *
@@ -959,6 +1022,28 @@ function delete_plugins( $plugins, $deprecated = '' ) {
 	return true;
 }
 
+/**
+ * Resumes a single plugin.
+ *
+ * Resuming the plugin basically means removing its entry from the
+ * `pause_on_admin` database option.
+ *
+ * @since 5.0.0
+ *
+ * @param string $plugin Single plugin to resume.
+ *
+ * @return bool|WP_Error True on success, false if `$plugin` was not paused, `WP_Error` on failure.
+ */
+function resume_plugin( $plugin ) {
+	$result = wp_forget_extension_error( 'plugins', $plugin );
+
+	if ( ! $result ) {
+		return new WP_Error( 'could_not_resume_plugin', __( 'Could not resume execution of the plugin.' ) );
+	}
+
+	return true;
+}
+
 /**
  * Validate active plugins
  *
@@ -2066,3 +2151,35 @@ function wp_add_privacy_policy_content( $plugin_name, $policy_text ) {
 
 	WP_Privacy_Policy_Content::add( $plugin_name, $policy_text );
 }
+
+/**
+ * Renders an admin notice in case some plugins have been paused due to errors.
+ *
+ * @since 5.0.0
+ *
+ * @return void
+ */
+function paused_plugins_notice() {
+	if ( 'plugins.php' === $GLOBALS['pagenow'] ) {
+		return;
+	}
+
+	if ( ! current_user_can( 'deactivate_plugins' ) ) {
+		return;
+	}
+
+	if ( ! isset( $GLOBALS['_paused_plugins'] ) || empty( $GLOBALS['_paused_plugins'] ) ) {
+		return;
+	}
+
+	echo sprintf(
+		'<div class="notice notice-error"><p><strong>%s</strong><br>%s</p><p>%s</p></div>',
+		__( 'One or more plugins failed to load properly.' ),
+		__( 'You can find more details and make changes on the Plugins screen.' ),
+		sprintf(
+			'<a href="%s">%s</a>',
+			admin_url( 'plugins.php?plugin_status=paused' ),
+			'Go to the Plugins screen'
+		)
+	);
+}

src/wp-admin/plugins.php

@@ -389,6 +389,27 @@
 			}
 			break;
 
+		case 'resume':
+			if ( ! current_user_can( 'resume_plugin', $plugin ) ) {
+				wp_die( __( 'Sorry, you are not allowed to resume execution of this plugin.' ) );
+			}
+
+			if ( is_multisite() && ! is_network_admin() && is_network_only_plugin( $plugin ) ) {
+				wp_redirect( self_admin_url( "plugins.php?plugin_status=$status&paged=$page&s=$s" ) );
+				exit;
+			}
+
+			check_admin_referer( 'resume-plugin_' . $plugin );
+
+			$result = resume_plugin( $plugin );
+
+			if ( is_wp_error( $result ) ) {
+				wp_die( $result );
+			}
+
+			wp_redirect( self_admin_url( "plugins.php?resume=true&plugin_status=$status&paged=$page&s=$s" ) );
+			exit;
+
 		default:
 			if ( isset( $_POST['checked'] ) ) {
 				check_admin_referer( 'bulk-plugins' );
@@ -532,6 +553,8 @@
 	<div id="message" class="updated notice is-dismissible"><p><?php _e( 'Selected plugins <strong>deactivated</strong>.' ); ?></p></div>
 <?php elseif ( 'update-selected' == $action ) : ?>
 	<div id="message" class="updated notice is-dismissible"><p><?php _e( 'All selected plugins are up to date.' ); ?></p></div>
+<?php elseif ( isset( $_GET['resume'] ) ) : ?>
+	<div id="message" class="updated notice is-dismissible"><p><?php _e( 'Execution of plugin <strong>resumed</strong>.' ); ?></p></div>
 <?php endif; ?>
 
 <div class="wrap">

src/wp-includes/capabilities.php

@@ -455,6 +455,7 @@ function map_meta_cap( $cap, $user_id ) {
 		case 'deactivate_plugins':
 		case 'activate_plugin':
 		case 'deactivate_plugin':
+		case 'resume_plugin':
 			$caps[] = 'activate_plugins';
 			if ( is_multisite() ) {
 				// update_, install_, and delete_ are handled above with is_super_admin().