Listen for hooks within set bounds

classes/Dispatcher.php

@@ -41,6 +41,9 @@ public function __construct( QM_Plugin $qm ) {
 		if ( ! defined( 'QM_EDITOR_COOKIE' ) ) {
 			define( 'QM_EDITOR_COOKIE', 'wp-query_monitor_editor_' . COOKIEHASH );
 		}
+		if ( ! defined( 'QM_MAX_DISCOVERED_HOOKS' ) ) {
+			define( 'QM_MAX_DISCOVERED_HOOKS', 100 );
+		}
 
 		add_action( 'init', array( $this, 'init' ) );
 

collectors/hooks_discovered.php

@@ -0,0 +1,206 @@
+<?php
+/**
+ * Hooks within bounds collector.
+ *
+ * @package query-monitor
+ */
+
+/**
+ * @extends QM_DataCollector<QM_Data_Hooks_Discovered>
+ */
+class QM_Collector_Hooks_Discovered extends QM_DataCollector {
+
+	public $id = 'hooks_discovered';
+
+	public function get_storage(): QM_Data {
+		return new QM_Data_Hooks_Discovered();
+	}
+
+	/**
+	 * @return string
+	 */
+	public function name() {
+		return __( 'Discovered Hooks', 'query-monitor' );
+	}
+
+	/**
+	 * @return void
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		if ( defined( 'QM_DISABLED_HOOK_DISCOVERY' ) && constant( 'QM_DISABLED_HOOK_DISCOVERY' ) ) {
+			return;
+		}
+
+		add_action( 'qm/listen/start', array( $this, 'action_listener_start' ) );
+		add_action( 'qm/listen/stop', array( $this, 'action_listener_stop' ) );
+		add_action( 'shutdown', array( $this, 'action_shutdown' ) );
+	}
+
+	/**
+	 * @return void
+	 */
+	public function tear_down() {
+		parent::tear_down();
+
+		remove_action( 'qm/listen/start', array( $this, 'action_listener_start' ) );
+		remove_action( 'qm/listen/stop', array( $this, 'action_listener_stop' ) );
+		remove_action( 'shutdown', array( $this, 'action_shutdown' ) );
+	}
+
+	/**
+	 * @param string $id
+	 * @return void
+	 */
+	public function action_listener_start( string $id ) {
+		if ( $this->is_active( $id ) ) {
+			return;
+		}
+
+		if ( is_array( $this->data->bounds ) && 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' ),
+				esc_html( $id ),
+			), E_USER_NOTICE );
+
+			return;
+		}
+
+		$this->maybe_add_all_callback();
+
+		if ( ! is_array( $this->data->active ) ) {
+			$this->data->active = array();
+		}
+
+		if ( ! is_array( $this->data->hooks ) ) {
+			$this->data->hooks = array();
+		}
+
+		if ( ! is_array( $this->data->counts ) ) {
+			$this->data->counts = array();
+		}
+
+		if ( ! is_array( $this->data->bounds ) ) {
+			$this->data->bounds = array();
+		}
+
+		$this->data->active[ $id ] = 1;
+		$this->data->hooks[ $id ]  = array();
+		$this->data->counts[ $id ] = 0;
+		$this->data->bounds[ $id ] = array(
+			'start' => new QM_Backtrace(),
+			'stop'  => null,
+		);
+	}
+
+	/**
+	 * @param string $id
+	 * @return void
+	 */
+	public function action_listener_stop( string $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' ),
+				esc_html( $id )
+			), E_USER_NOTICE );
+
+			return;
+		}
+
+		unset( $this->data->active[ $id ] );
+		$this->data->bounds[ $id ]['stop'] = new QM_Backtrace();
+
+		if ( $this->is_active() ) {
+			return;
+		}
+
+		remove_filter( 'all', array( $this, 'filter_all' ) );
+	}
+
+	/**
+	 * @param mixed $var
+	 * @return mixed
+	 */
+	public function filter_all( $var ) {
+		if ( ! $this->is_active() ) {
+			remove_filter( 'all', array( $this, 'filter_all' ) );
+
+			return $var;
+		}
+
+		if ( in_array( current_action(), array(
+			'qm/listen/start',
+			'qm/listen/stop',
+		) ) ) {
+			return $var;
+		}
+
+		global $wp_actions;
+
+		foreach ( array_keys( $this->data->active ) as $id ) {
+			end( $this->data->hooks[ $id ] );
+			$last = current( $this->data->hooks[ $id ] );
+
+			if ( ! empty( $last ) && current_action() === $last['name'] ) {
+				$i = absint( key( $this->data->hooks[ $id ] ) );
+				$this->data->hooks[ $id ][ $i ]['fires']++;
+			} else {
+				$this->data->hooks[ $id ][] = array(
+					'name'      => current_action(),
+					'is_action' => array_key_exists( current_action(), $wp_actions ),
+					'fires'     => 1,
+				);
+			}
+
+			if ( constant( 'QM_MAX_DISCOVERED_HOOKS' ) < ++$this->data->counts[ $id ] ) {
+				$this->action_listener_stop( $id );
+				$this->data->bounds[ $id ]['terminated'] = true;
+			}
+
+			return $var;
+		}
+	}
+
+	/**
+	 * @return void
+	 */
+	public function action_shutdown() {
+		if ( ! $this->is_active() ) {
+			return;
+		}
+
+		foreach ( array_keys( $this->data->active ) as $id ) {
+			$this->action_listener_stop( $id );
+		}
+	}
+
+	/**
+	 * @param string $id
+	 * @return bool
+	 */
+	protected function is_active( string $id = '' ) {
+		if ( empty( $id ) ) {
+			return ! empty( $this->data->active );
+		}
+
+		return is_array( $this->data->active ) && array_key_exists( $id, $this->data->active );
+	}
+
+	/**
+	 * @return void
+	 */
+	protected function maybe_add_all_callback() {
+		if ( $this->is_active() ) {
+			return;
+		}
+
+		add_filter( 'all', array( $this, 'filter_all' ) );
+	}
+
+}
+
+# Load early to catch all hooks
+QM_Collectors::add( new QM_Collector_Hooks_Discovered() );

data/hooks_discovered.php

@@ -0,0 +1,28 @@
+<?php declare(strict_types = 1);
+/**
+ * Hooks data transfer object.
+ *
+ * @package query-monitor
+ */
+
+class QM_Data_Hooks_Discovered extends QM_Data {
+	/**
+	 * @var array<string, int>
+	 */
+	public $active;
+
+	/**
+	 * @var array<string, array<string, mixed>>
+	 */
+	public $bounds;
+
+	/**
+	 * @var array<string, int>
+	 */
+	public $counts;
+
+	/**
+	 * @var array<string, array<int, array<string, mixed>>>
+	 */
+	public $hooks;
+}

dispatchers/Html.php

@@ -663,6 +663,14 @@ protected function after_output() {
 				'label' => __( 'Allow the wp-content/db.php file symlink to be put into place during activation. Set to false to prevent the symlink creation.', 'query-monitor' ),
 				'default' => true,
 			),
+			'QM_DISABLED_HOOK_DISCOVERY' => array(
+				'label' => __( 'Prevent hook discovery, to safeguard against performance impact in production.', 'query-monitor' ),
+				'default' => false,
+			),
+			'QM_MAX_DISCOVERED_HOOKS' => array(
+				'label' => __( 'Maximum number of hooks to discover before terminating.', 'query-monitor' ),
+				'default' => 100,
+			),
 		);
 
 		/**