Listen for hooks firing within set bounds

assets/_styles.scss

@@ -590,7 +590,8 @@ body.admin-color-light #wp-admin-bar-query-monitor:not(.qm-all-clear):not(:hover
 		margin: 20px !important;
 	}
 
-	.qm-concerns table {
+	.qm-concerns table,
+	.qm-discovered table {
 		border-top: 1px solid $qm-cell-border !important;
 		margin-bottom: 20px !important;
 	}

assets/query-monitor.css

@@ -539,7 +539,8 @@ body.admin-color-light #wp-admin-bar-query-monitor:not(.qm-all-clear):not(:hover
   font-size: 14px !important;
   margin: 20px !important;
 }
-#query-monitor-main .qm-concerns table {
+#query-monitor-main .qm-concerns table,
+#query-monitor-main .qm-discovered table {
   border-top: 1px solid #e0e0e0 !important;
   margin-bottom: 20px !important;
 }

classes/Dispatcher.php

@@ -15,6 +15,10 @@ public function __construct( QM_Plugin $qm ) {
 			define( 'QM_COOKIE', 'wp-query_monitor_' . COOKIEHASH );
 		}
 
+		if ( ! defined( 'QM_MAX_HOOKS_DISCOVERED' ) ) {
+			define( 'QM_MAX_HOOKS_DISCOVERED', 500 );
+		}
+
 		add_action( 'init', array( $this, 'init' ) );
 
 	}

collectors/hooks_within_bounds.php

@@ -0,0 +1,138 @@
+<?php
+/**
+ * Hooks within bounds collector.
+ *
+ * @package query-monitor
+ */
+
+class QM_Collector_Hooks_Within_Bounds extends QM_Collector {
+
+	public $id = 'hooks_within_bounds';
+	private $active = array();
+
+	public function name() {
+		return __( 'Discovered Hooks', 'query-monitor' );
+	}
+
+	public function __construct() {
+		parent::__construct();
+
+		if ( defined( 'QM_DISABLE_HOOK_DISCOVERY' ) && QM_DISABLE_HOOK_DISCOVERY ) {
+			return;
+		}
+
+		add_action( 'qm/listen/start', array( $this, 'action_function_listener_start' ) );
+		add_action( 'qm/listen/stop',  array( $this, 'action_function_listener_stop'  ) );
+		add_action( 'shutdown',        array( $this, 'action_function_shutdown'       ) );
+
+		$this->data = array(
+			'hooks'  => array(),
+			'bounds' => array(),
+			'counts' => array(),
+		);
+	}
+
+	function action_function_listener_start( $id ) {
+		if ( $this->is_active( $id ) ) {
+			return;
+		}
+
+		if ( array_key_exists( $id, $this->data['bounds'] ) ) {
+			trigger_error( sprintf(
+				/* translators: %s: Hook discovery ID */
+				esc_html__( 'Hook discovery ID %s already exists', 'query-monitor' ),
+				'<code>' . $id . '</code>'
+			), E_USER_NOTICE );
+			return;
+		}
+
+		$this->maybe_add_all_callback();
+
+		$this->active[ $id ] = 1;
+		$this->data['hooks'][ $id ] = array();
+		$this->data['bounds'][ $id ] = array(
+			'start' => new QM_Backtrace(),
+			'stop'  => null,
+		);
+		$this->data['counts'][ $id ] = 0;
+	}
+
+	function action_function_all( $var = null ) {
+		if ( ! $this->is_active() ) {
+			remove_action( 'all', array( $this, 'action_function_all' ) );
+			return $var;
+		}
+
+		if ( in_array( current_action(), array(
+			'qm/listen/start',
+			'qm/listen/stop',
+		) ) ) {
+			return $var;
+		}
+
+		global $wp_actions;
+
+		foreach ( array_keys( $this->active ) as $id ) {
+			end( $this->data['hooks'][ $id ] );
+			$last = current( $this->data['hooks'][ $id ] );
+
+			if ( current_action() === $last['hook'] ) {
+				$i = key( $this->data['hooks'][ $id ] );
+				$this->data['hooks'][ $id ][ $i ]['fires']++;
+			} else {
+				$this->data['hooks'][ $id ][] = array(
+					'hook'      => current_action(),
+					'is_action' => array_key_exists( current_action(), $wp_actions ),
+					'fires'     => 1,
+				);
+			}
+
+			if ( QM_MAX_HOOKS_DISCOVERED < ++$this->data['counts'][ $id ] ) {
+				$this->action_function_listener_stop( $id );
+				$this->data['bounds'][ $id ]['was_terminated'] = true;
+			}
+
+			return $var;
+		}
+	}
+
+	function action_function_listener_stop( $id ) {
+		if ( ! $this->is_active( $id ) && ! array_key_exists( $id, $this->data['hooks'] ) ) {
+			trigger_error( sprintf(
+				/* translators: %s: Hook discovery ID */
+				esc_html__( 'Hook discovery starting bound for %s has not been set', 'query-monitor' ),
+				'<code>' . $id . '</code>'
+			), E_USER_NOTICE );
+			return;
+		}
+
+		unset( $this->active[ $id ] );
+		$this->data['bounds'][ $id ]['stop'] = new QM_Backtrace();
+
+		if ( ! $this->is_active() ) {
+			remove_action( 'all', array( $this, 'action_function_all' ) );
+		}
+	}
+
+	function action_function_shutdown() {
+		if ( $this->is_active() ) {
+			foreach ( array_keys( $this->active ) as $id ) {
+				$this->action_function_listener_stop( $id );
+			}
+		}
+	}
+
+	function is_active( $id = false ) {
+		return false !== $id ? array_key_exists( $id, $this->active ) : ! empty( $this->active );
+	}
+
+	function maybe_add_all_callback() {
+		if ( ! $this->is_active() ) {
+			add_action( 'all', array( $this, 'action_function_all' ), 0 );
+		}
+	}
+
+}
+
+# Load early so early hooks can be discovered
+QM_Collectors::add( new QM_Collector_Hooks_Within_Bounds() );

dispatchers/Html.php

@@ -381,39 +381,47 @@ protected function after_output() {
 
 		echo '<div class="qm-boxed">';
 		$constants = array(
-			'QM_DB_EXPENSIVE'          => array(
+			'QM_DB_EXPENSIVE'           => array(
 				/* translators: %s: The default value for a PHP constant */
 				'label'   => __( 'If an individual database query takes longer than this time to execute, it\'s considered "slow" and triggers a warning. Default value: %s.', 'query-monitor' ),
 				'default' => 0.05,
 			),
-			'QM_DISABLED'              => array(
+			'QM_DISABLED'               => array(
 				'label'   => __( 'Disable Query Monitor entirely.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_DISABLE_ERROR_HANDLER' => array(
+			'QM_DISABLE_ERROR_HANDLER'  => array(
 				'label'   => __( 'Disable the handling of PHP errors.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_ENABLE_CAPS_PANEL'     => array(
+			'QM_ENABLE_CAPS_PANEL'      => array(
 				'label'   => __( 'Enable the Capability Checks panel.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_HIDE_CORE_ACTIONS'     => array(
+			'QM_HIDE_CORE_ACTIONS'      => array(
 				'label'   => __( 'Hide WordPress core on the Hooks & Actions panel.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_HIDE_SELF'             => array(
+			'QM_HIDE_SELF'              => array(
 				'label'   => __( 'Hide Query Monitor itself from various panels.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_NO_JQUERY'             => array(
+			'QM_NO_JQUERY'              => array(
 				'label'   => __( 'Don\'t specify jQuery as a dependency of Query Monitor. If jQuery isn\'t enqueued then Query Monitor will still operate, but with some reduced functionality.', 'query-monitor' ),
 				'default' => false,
 			),
-			'QM_SHOW_ALL_HOOKS'        => array(
+			'QM_SHOW_ALL_HOOKS'         => array(
 				'label'   => __( 'In the Hooks & Actions panel, show every hook that has an action or filter attached (instead of every action hook that fired during the request).', 'query-monitor' ),
 				'default' => false,
 			),
+			'QM_DISABLE_HOOK_DISCOVERY' => array(
+				'label'   => __( 'Prevent hook discovery, to safeguard against performance degradation in production.' ),
+				'default' => false,
+			),
+			'QM_MAX_HOOKS_DISCOVERED'   => array(
+				'label'   => __( 'Maximum number of hooks to discover before auto-terminating.' ),
+				'default' => 300,
+			)
 		);
 
 		echo '<section>';

output/html/hooks.php

@@ -96,11 +96,20 @@ public static function output_hook_table( array $hooks ) {
 						echo '<th scope="row" rowspan="' . intval( $rowspan ) . '" class="qm-nowrap qm-ltr"><span class="qm-sticky">';
 						echo '<code>' . esc_html( $hook['name'] ) . '</code>';
 						if ( 'all' === $hook['name'] ) {
+							$_hooks_within_bounds = QM_Collectors::get( 'hooks_within_bounds' );
+							$hooks_within_bounds  = $_hooks_within_bounds->get_data();
+
+							$extra = ' Try to avoid using it.';
+
+							if ( $_hooks_within_bounds && !empty( $hooks_within_bounds['hooks'] ) )
+								$extra = '<br />Remove or disable hook discovery when not actively using.'; // @TODO Link to panel.
+
 							echo '<br><span class="qm-warn"><span class="dashicons dashicons-warning" aria-hidden="true"></span>';
 							printf(
 								/* translators: %s: Action name */
-								esc_html__( 'Warning: The %s action is extremely resource intensive. Try to avoid using it.', 'query-monitor' ),
-								'<code>all</code>'
+								esc_html__( 'Warning: The %1$s action is extremely resource intensive.%2$s', 'query-monitor' ),
+								'<code>all</code>',
+								$extra
 							);
 							echo '<span>';
 						}

output/html/hooks_within_bounds.php

@@ -0,0 +1,136 @@
+<?php
+/**
+ * Hooks within bounds output for HTML pages.
+ *
+ * @package query-monitor
+ */
+
+class QM_Output_Html_Hooks_Within_Bounds extends QM_Output_Html {
+
+	public $id = 'hooks_within_bounds';
+
+	public function __construct( QM_Collector $collector ) {
+		parent::__construct( $collector );
+		add_filter( 'qm/output/panel_menus', array( $this, 'panel_menu' ), 80 );
+	}
+
+	public function panel_menu( array $menu ) {
+		$hooks     = QM_Collectors::get( 'hooks' );
+		$collector = QM_Collectors::get( 'hooks_within_bounds' );
+
+		if ( $hooks && $collector ) {
+			$menu['qm-hooks']['children'][] = $this->menu( array(
+				'title' => '└ ' . esc_html__( 'Discovered Hooks', 'query-monitor' ),
+			) );
+		}
+
+		return $menu;
+	}
+
+	public function output() {
+		$data = $this->collector->get_data();
+
+		if ( empty( $data['hooks'] ) ) {
+			$this->before_non_tabular_output();
+
+			$_notice = 'No discovered hooks.';
+
+			if ( defined( 'QM_DISABLE_HOOK_DISCOVERY' ) && QM_DISABLE_HOOK_DISCOVERY ) {
+				$_notice = 'Hook discovery disabled.';
+			}
+
+			$notice = __( $_notice, 'query-monitor' );
+			echo $this->build_notice( $notice ); // WPCS: XSS ok.
+
+			$this->after_non_tabular_output();
+			return;
+		}
+
+		printf(
+			'<div class="qm qm-discovered" id="%1$s" role="group" aria-labelledby="%1$s" tabindex="-1">',
+			esc_attr( $this->collector->id() )
+		);
+
+		echo '<div><table>';
+
+		printf(
+			'<caption><h2 id="%1$s-caption">%2$s</h2></caption>',
+			esc_attr( $this->collector->id() ),
+			esc_html__( 'Discovered Hooks', 'query-monitor' )
+		);
+
+		echo '<thead>';
+		echo '<tr>';
+		echo '<th scope="col">' . esc_html__( 'Label', 'query-monitor' ) . '</th>';
+		echo '<th scope="col"></th>';
+		echo '<th scope="col">' . esc_html__( 'Hook',  'query-monitor' ) . '</th>';
+		echo '<th scope="col">' . esc_html__( 'Type',  'query-monitor' ) . '</th>';
+		echo '</tr>';
+		echo '</thead>';
+
+		echo '<tbody>';
+
+		foreach ( $data['hooks'] as $id => $hooks ) {
+			$trace_file__start
+				= $trace_file__stop
+				= '';
+
+			$bound__start = $data['bounds'][ $id ]['start'];
+			$bound__stop  = $data['bounds'][ $id ]['stop'];
+
+			if ( is_a( $bound__start, 'QM_Backtrace' ) ) {
+				$trace__start = $bound__start->get_trace();
+				$trace_text__start = self::output_filename( '', $trace__start[0]['file'], $trace__start[0]['line'] );
+			}
+
+			if ( !empty( $data['bounds'][ $id ]['was_terminated'] ) ) {
+				$trace_text__stop = '<br /><span class="qm-info qm-supplemental">Auto-terminated (<abbr title="' . QM_MAX_HOOKS_DISCOVERED . '">max hooks</abbr>)</span>';
+			} else if ( is_a( $bound__stop, 'QM_Backtrace' ) ) {
+				$trace__stop = $bound__stop->get_trace();
+				$trace_text__stop = self::output_filename( '', $trace__stop[0]['file'], $trace__stop[0]['line'] );
+			}
+
+			foreach ( $hooks as $i => $hook ) {
+				echo '<tr>';
+
+				if ( 0 === $i ) {
+					echo '<th scope="row" rowspan="' . esc_attr( count( $hooks ) ) . '" class="qm-nowrap">';
+					echo '<span class="qm-sticky">';
+					echo esc_html( $id );
+					echo $trace_text__start; // WPCS: XSS ok.
+					echo $trace_text__stop;  // WPCS: XSS ok.
+					echo '</span>';
+					echo '</th>';
+				}
+
+				echo '<td class="qm-num">' . esc_html( ++$i ) . '</td>';
+
+				echo '<td>';
+				echo '<code>' . esc_html( $hook['hook'] ) . '</code>';
+
+				if ( 1 < $hook['fires'] ) {
+					echo '<br /><span class="qm-info qm-supplemental">Fired ' . esc_html( $hook['fires'] ) . ' times</span>';
+				}
+				echo '</td>';
+				echo '<td>' . ( $hook['is_action'] ? 'Action' : 'Filter' ) . '</td>';
+				echo '</tr>';
+			}
+		}
+
+		echo '</tbody>';
+		echo '</table></div>';
+
+		echo '</div>';
+	}
+
+}
+
+function register_qm_output_html_hooks_within_bounds( array $output, QM_Collectors $collectors ) {
+	$collector = $collectors::get( 'hooks_within_bounds' );
+	if ( $collector ) {
+		$output['hooks_within_bounds'] = new QM_Output_Html_Hooks_Within_Bounds( $collector );
+	}
+	return $output;
+}
+
+add_filter( 'qm/outputter/html', 'register_qm_output_html_hooks_within_bounds', 80, 2 );