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wp-content/plugins/jetpack-boost/app/lib/class-setup.php

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+<?php
+
+namespace Automattic\Jetpack_Boost\Lib;
+
+use Automattic\Jetpack_Boost\Contracts\Has_Setup;
+
+class Setup {
+
+	protected static $instances = array();
+
+	/**
+	 * This method takes a `Has_Setup` instance and registers the setup action.
+	 * In addition, it will keep track of all the instances passed to it,
+	 *
+	 * This is useful if a plugin needs the instance
+	 * to modify the behavior at a certain hook that
+	 * Jetpack Boost is using.
+	 *
+	 * The use case would be something like this:
+	 * ```
+	 *      $instance = my_get_instance_method( Setup::get_instances() );
+	 *      remove_action( 'wp_footer', array( $instance, 'foobar' ) );
+	 * ```
+	 *
+	 * @param Has_Setup $instance
+	 *
+	 * @return void
+	 */
+	public static function add( Has_Setup $instance ) {
+		$instance->setup();
+
+		self::$instances[] = $instance;
+	}
+
+	public static function get_instances() {
+		return self::$instances;
+	}
+
+	/**
+	 * @template T
+	 * @param class-string<T> $class_name
+	 * @return T|null
+	 */
+	public static function get_instance_of( $class_name ) {
+		foreach ( self::get_instances() as $instance ) {
+			if ( $instance instanceof $class_name ) {
+				// @phan-suppress-next-line PhanTypeMismatchReturn -- Phan isn't inferring the type correctly from the `instanceof $class_name` like it's supposed to.
+				return $instance;
+			}
+		}
+
+		return null;
+	}
+}