amp-query-monitor-compat.php

<?php
/**
 * AMP Query Monitor Compat
 *
 * @package   AMP_Query_Monitor_Compat
 * @author    Weston Ruter, Google
 * @license   GPL-2.0-or-later
 * @copyright 2019 Google LLC
 *
 * @wordpress-plugin
 * Plugin Name: AMP Query Monitor Compat
 * Description: Integrate Query Monitor with AMP dev mode so that its scripts/styles are not removed in the sanitization process. Depends on <a href="https://wordpress.org/plugins/amp/">AMP plugin</a> <a href="https://github.com/ampproject/amp-wp/releases/tag/1.3-beta1">v1.3-beta1</a>+.
 * Plugin URI: https://gist.github.com/westonruter/621137b5a5ae1caaaee48c63f61ce7b7
 * Version: 0.1.0
 * Author: Weston Ruter, Google
 * Author URI: https://weston.ruter.net/
 * License: GNU General Public License v2 (or later)
 * License URI: http://www.gnu.org/licenses/gpl-2.0.html
 * Gist Plugin URI: https://gist.github.com/westonruter/621137b5a5ae1caaaee48c63f61ce7b7
 */

namespace AMP_Query_Monitor_Compat;

/**
 * Determine whether it is an AMP request.
 *
 * @return bool Whether AMP.
 */
function is_amp() {
	return function_exists( 'is_amp_endpoint' ) && is_amp_endpoint();
}

/**
 * Add inline scripts added by Query Monitor to AMP dev mode.
 *
 * @param string[] $xpaths XPaths.
 * @return string[] XPaths.
 */
function add_dev_mode_attributes( $xpaths ) {
	$xpaths[] = '//script[ contains( text(), "qm_number_format" ) ]';
	$xpaths[] = '//script[ contains( text(), "QM_i18n" ) ]';
	$xpaths[] = '//script[ contains( text(), "query-monitor-" ) ]';
	return $xpaths;
}

add_filter( 'amp_dev_mode_element_xpaths', __NAMESPACE__ . '\add_dev_mode_attributes' );

/**
 * Get all dependency handles for the supplied handles.
 *
 * @see \WP_Dependencies::all_deps()
 *
 * @param \WP_Dependencies $dependencies Dependencies.
 * @param string[]         $handles      Handles.
 * @return string[] Dependency handles.
 */
function get_all_deps( \WP_Dependencies $dependencies, $handles ) {
	$dependency_handles = [];
	foreach ( $handles as $handle ) {
		if ( isset( $dependencies->registered[ $handle ] ) ) {
			$dependency_handles = array_merge(
				$dependency_handles,
				$dependencies->registered[ $handle ]->deps,
				get_all_deps( $dependencies, $dependencies->registered[ $handle ]->deps )
			);
		}
	}
	return $dependency_handles;
}

/**
 * Mark Query Monitor assets as being part of AMP dev mode.
 */
function make_query_monitor_scripts_dependent_on_admin_bar() {
	if ( ! is_amp() ) {
		return;
	}

	$qm_handle = 'query-monitor';

	if ( wp_script_is( $qm_handle, 'enqueued' ) ) {
		$script_dependencies = array_merge( [ $qm_handle ], get_all_deps( wp_scripts(), [ $qm_handle ] ) );
		add_filter(
			'script_loader_tag',
			function ( $tag, $handle ) use ( $script_dependencies ) {
				if ( in_array( $handle, $script_dependencies, true ) ) {
					$tag = preg_replace( '/(?<=<script)(?=\s|>)/i', ' data-ampdevmode', $tag );
				}
				return $tag;
			},
			10,
			2
		);
	}

	if ( wp_style_is( $qm_handle, 'enqueued' ) ) {
		$style_dependencies = array_merge( [ $qm_handle ], get_all_deps( wp_styles(), [ $qm_handle ] ) );
		add_filter(
			'style_loader_tag',
			function ( $tag, $handle ) use ( $style_dependencies ) {
				if ( in_array( $handle, $style_dependencies, true ) ) {
					$tag = preg_replace( '/(?<=<link)(?=\s|>)/i', ' data-ampdevmode', $tag );
				}
				return $tag;
			},
			10,
			2
		);
	}
}
add_action( 'wp_enqueue_scripts', __NAMESPACE__ . '\make_query_monitor_scripts_dependent_on_admin_bar' );

Installation instructions: https://gist.github.com/westonruter/6110fbc4bef0c4b8c021a112012f7e9c