Add debugging query arguments

includes/amp-helper-functions.php

@@ -302,6 +302,11 @@ function is_amp_endpoint() {
 		return true;
 	}
 
+	// If a certain debugging flag is present, AMP should be disabled.
+	if ( AMP_Debug::has_flag( AMP_Debug::DISABLE_AMP_QUERY_VAR ) ) {
+		return false;
+	}
+
 	$has_amp_query_var = (
 		isset( $_GET[ amp_get_slug() ] ) // phpcs:ignore WordPress.Security.NonceVerification.Recommended
 		||

includes/class-amp-autoloader.php

@@ -102,6 +102,7 @@ class AMP_Autoloader {
 		'AMP_Validation_Callback_Wrapper'    => 'includes/validation/class-amp-validation-callback-wrapper',
 		'AMP_Validated_URL_Post_Type'        => 'includes/validation/class-amp-validated-url-post-type',
 		'AMP_Validation_Error_Taxonomy'      => 'includes/validation/class-amp-validation-error-taxonomy',
+		'AMP_Debug'                          => 'includes/validation/class-amp-debug',
 		'AMP_CLI_Namespace'                  => 'includes/cli/class-amp-cli-namespace',
 		'AMP_CLI_Validation_Command'         => 'includes/cli/class-amp-cli-validation-command',
 		'AMP_String_Utils'                   => 'includes/utils/class-amp-string-utils',

includes/class-amp-theme-support.php

@@ -498,7 +498,7 @@ public static function ensure_proper_amp_location( $exit = true ) {
 	 */
 	public static function redirect_non_amp_url( $status = 302, $exit = true ) {
 		$current_url = amp_get_current_url();
-		$non_amp_url = amp_remove_endpoint( $current_url );
+		$non_amp_url = remove_query_arg( AMP_Debug::AMP_FLAGS_QUERY_VAR, amp_remove_endpoint( $current_url ) );
 		if ( $non_amp_url === $current_url ) {
 			return false;
 		}
@@ -1906,6 +1906,10 @@ public static function start_output_buffering() {
 			newrelic_disable_autorum();
 		}
 
+		if ( AMP_Debug::has_flag( AMP_Debug::DISABLE_POST_PROCESSING_QUERY_VAR ) ) {
+			return;
+		}
+
 		ob_start( [ __CLASS__, 'finish_output_buffering' ] );
 		self::$is_output_buffering = true;
 	}
@@ -2041,6 +2045,8 @@ public static function prepare_response( $response, $args = [] ) {
 			! AMP_Validation_Manager::should_validate_response()
 			&&
 			! is_customize_preview()
+			&&
+			! AMP_Debug::has_flag( AMP_Debug::DISABLE_RESPONSE_CACHE_QUERY_VAR )
 		);
 
 		// When response caching is enabled, determine if it should be turned off for cache misses.
@@ -2155,7 +2161,15 @@ public static function prepare_response( $response, $args = [] ) {
 				AMP_HTTP::send_server_timing( 'amp_processor_cache_hit', -$prepare_response_start );
 
 				// Redirect to non-AMP version.
-				if ( ! amp_is_canonical() && ! is_singular( AMP_Story_Post_Type::POST_TYPE_SLUG ) && $blocking_error_count > 0 ) {
+				if (
+					! amp_is_canonical()
+					&&
+					! is_singular( AMP_Story_Post_Type::POST_TYPE_SLUG )
+					&&
+					$blocking_error_count > 0
+					&&
+					! AMP_Debug::has_flag( AMP_Debug::PREVENT_REDIRECT_TO_NON_AMP_QUERY_VAR )
+				) {
 					if ( AMP_Validation_Manager::has_cap() ) {
 						$non_amp_url = add_query_arg( AMP_Validation_Manager::VALIDATION_ERRORS_QUERY_VAR, $blocking_error_count, $non_amp_url );
 					}
@@ -2300,7 +2314,7 @@ public static function prepare_response( $response, $args = [] ) {
 					$script->appendChild( $dom->createTextNode( 'document.addEventListener( "DOMContentLoaded", function() { document.write = function( text ) { throw new Error( "[AMP-WP] Prevented document.write() call with: "  + text ); }; } );' ) );
 					$head->appendChild( $script );
 				}
-			} elseif ( ! self::is_customize_preview_iframe() ) {
+			} elseif ( ! self::is_customize_preview_iframe() && ! AMP_Debug::has_flag( AMP_Debug::PREVENT_REDIRECT_TO_NON_AMP_QUERY_VAR ) ) {
 				$response = esc_html__( 'Redirecting to non-AMP version.', 'amp' );
 
 				if ( $cache_response ) {
@@ -2312,6 +2326,9 @@ public static function prepare_response( $response, $args = [] ) {
 					$non_amp_url = add_query_arg( AMP_Validation_Manager::VALIDATION_ERRORS_QUERY_VAR, $blocking_error_count, $non_amp_url );
 				}
 
+				// Remove debugging query args.
+				$non_amp_url = remove_query_arg( AMP_Debug::AMP_FLAGS_QUERY_VAR, $non_amp_url );
+
 				/*
 				 * Temporary redirect because AMP page may return with blocking validation errors when auto-accepting sanitization
 				 * is not enabled. A 302 will allow the errors to be fixed without needing to bust any redirect caches.

includes/sanitizers/class-amp-style-sanitizer.php

@@ -2627,7 +2627,7 @@ private function finalize_styles() {
 					esc_html__( 'The %s element is populated with:', 'amp' ),
 					'style[amp-custom]'
 				) . "\n" . implode( "\n", $included_sources ) . "\n";
-				if ( self::has_required_php_css_parser() ) {
+				if ( self::has_required_php_css_parser() && ! AMP_Debug::has_flag( AMP_Debug::DISABLE_TREE_SHAKING_QUERY_VAR ) ) {
 					$comment .= sprintf(
 						/* translators: 1: number of included bytes. 2: percentage of total CSS actually included after tree shaking. 3: total included size. */
 						esc_html__( 'Total included size: %1$s bytes (%2$d%% of %3$s total after tree shaking)', 'amp' ),
@@ -3033,7 +3033,7 @@ function( $id ) {
 							$this->has_used_attributes( $parsed_selector[ self::SELECTOR_EXTRACTED_ATTRIBUTES ] )
 						)
 					);
-					if ( $should_include ) {
+					if ( $should_include || AMP_Debug::has_flag( AMP_Debug::DISABLE_TREE_SHAKING_QUERY_VAR ) ) {
 						$selectors[] = $selector;
 					}
 				}
@@ -3130,7 +3130,7 @@ function( $a, $b ) {
 			}
 
 			// Report validation error if size is now too big.
-			if ( $current_concatenated_size + $this->pending_stylesheets[ $i ]['size'] > $max_bytes ) {
+			if ( $current_concatenated_size + $this->pending_stylesheets[ $i ]['size'] > $max_bytes && ! AMP_Debug::has_flag( AMP_Debug::DISABLE_TREE_SHAKING_QUERY_VAR ) ) {
 				$validation_error = [
 					'code' => 'excessive_css',
 					'type' => AMP_Validation_Error_Taxonomy::CSS_ERROR_TYPE,

includes/validation/class-amp-debug.php

@@ -0,0 +1,119 @@
+<?php
+/**
+ * Class AMP_Debug
+ *
+ * @package AMP
+ */
+
+/**
+ * Class AMP_Debug
+ *
+ * @since 1.4.1
+ */
+final class AMP_Debug {
+
+	/**
+	 * A top-level query var for AMP flags.
+	 *
+	 * Debugging query vars should follow this.
+	 * For example, https://example.com/?amp&amp_flags[disable_post_processing]=1
+	 *
+	 * @var string
+	 */
+	const AMP_FLAGS_QUERY_VAR = 'amp_flags';
+
+	/**
+	 * A query var to disable post processing.
+	 *
+	 * @var string
+	 */
+	const DISABLE_POST_PROCESSING_QUERY_VAR = 'disable_post_processing';
+
+	/**
+	 * A query var to disable the response cache.
+	 *
+	 * @var string
+	 */
+	const DISABLE_RESPONSE_CACHE_QUERY_VAR = 'disable_response_cache';
+
+	/**
+	 * A query var to prevent a redirect to a non-AMP URL.
+	 *
+	 * @var string
+	 */
+	const PREVENT_REDIRECT_TO_NON_AMP_QUERY_VAR = 'prevent_redirect';
+
+	/**
+	 * A query var to disable tree shaking.
+	 *
+	 * @var string
+	 */
+	const DISABLE_TREE_SHAKING_QUERY_VAR = 'disable_tree_shaking';
+
+	/**
+	 * Query var to reject all validation errors.
+	 *
+	 * @var string
+	 */
+	const REJECT_ALL_VALIDATION_ERRORS_QUERY_VAR = 'reject_all_errors';
+
+	/**
+	 * Query var to accept 'excessive_css' validation errors.
+	 *
+	 * @var string
+	 */
+	const ACCEPT_EXCESSIVE_CSS_ERROR_QUERY_VAR = 'accept_excessive_css';
+
+	/**
+	 * Query var to disable AMP.
+	 *
+	 * @var string
+	 */
+	const DISABLE_AMP_QUERY_VAR = 'disable_amp';
+
+	/**
+	 * Gets whether the flag as a query var should be considered true.
+	 *
+	 * If the flag is present but '', this will be true, like &amp_flags[disable_amp].
+	 * It will also be true if it is '1' or 'true', but false for most other values.
+	 * The flag should be after the top-level flag of 'amp_flags'.
+	 * For example, with the flag 'disable_amp':
+	 * https://example.com/?amp&amp_flags[disable_amp]=1
+	 *
+	 * @param string $flag The name of the flag (query var).
+	 * @return bool Whether the flag as a query var should be considered true.
+	 */
+	public static function has_flag( $flag ) {
+		if ( ! isset( $_GET[ self::AMP_FLAGS_QUERY_VAR ][ $flag ] ) ) { // phpcs:ignore WordPress.Security.NonceVerification.Recommended
+			return false;
+		}
+
+		$flag_query_var = $_GET[ self::AMP_FLAGS_QUERY_VAR ][ $flag ]; // phpcs:ignore WordPress.Security.NonceVerification.Recommended
+		if (
+			array_key_exists( $flag, self::get_all_query_vars() )
+			&&
+			AMP_Validation_Manager::has_cap()
+		) {
+			return '' === $flag_query_var ? true : filter_var( $flag_query_var, FILTER_VALIDATE_BOOLEAN );
+		}
+
+		return false;
+	}
+
+	/**
+	 * Gets all of the debugging query vars.
+	 *
+	 * @return array An associative array of query var name => title.
+	 */
+	public static function get_all_query_vars() {
+		return [
+			self::DISABLE_POST_PROCESSING_QUERY_VAR      => __( 'Disable post-processing', 'amp' ),
+			self::DISABLE_RESPONSE_CACHE_QUERY_VAR       => __( 'Disable response cache', 'amp' ),
+			self::PREVENT_REDIRECT_TO_NON_AMP_QUERY_VAR  => __( 'Prevent redirect', 'amp' ),
+			self::REJECT_ALL_VALIDATION_ERRORS_QUERY_VAR => __( 'Reject all errors', 'amp' ),
+			self::ACCEPT_EXCESSIVE_CSS_ERROR_QUERY_VAR   => __( 'Accept excessive CSS', 'amp' ),
+			self::DISABLE_AMP_QUERY_VAR                  => __( 'Disable AMP', 'amp' ),
+			self::DISABLE_TREE_SHAKING_QUERY_VAR         => __( 'Disable tree shaking', 'amp' ),
+		];
+	}
+}

includes/validation/class-amp-validation-error-taxonomy.php

@@ -274,6 +274,7 @@ public static function register() {
 		}
 
 		self::accept_validation_errors( AMP_Core_Theme_Sanitizer::get_acceptable_errors( get_template() ) );
+		add_filter( 'amp_validation_error_sanitized', [ __CLASS__, 'conditionally_change_sanitization' ], 10, 2 );
 	}
 
 	/**
@@ -2859,4 +2860,32 @@ public static function get_status_text_with_icon( $sanitization ) {
 		}
 		return sprintf( '<span class="status-text %s">%s</span>', esc_attr( $class ), esc_html( $text ) );
 	}
+
+	/**
+	 * Possibly changes the sanitization of an error, based on the presence of query vars and the proper permission.
+	 *
+	 * This enables rejecting all validation errors, given the proper permissions and a query var.
+	 * Likewise, it enables accepting only 'excessive_css' errors.
+	 *
+	 * @param bool|null $sanitized A boolean to change the sanitization of the error, or null to not change it.
+	 * @param array     $error The error to examine.
+	 * @return bool|null The filtered sanitization, false meaning that it will be rejected, and null meaning to not change the sanitization.
+	 */
+	public static function conditionally_change_sanitization( $sanitized, $error ) {
+		if ( AMP_Debug::has_flag( AMP_Debug::REJECT_ALL_VALIDATION_ERRORS_QUERY_VAR ) ) {
+			return false;
+		}
+
+		if (
+			AMP_Debug::has_flag( AMP_Debug::ACCEPT_EXCESSIVE_CSS_ERROR_QUERY_VAR )
+			&&
+			isset( $error['code'] )
+			&&
+			'excessive_css' === $error['code']
+		) {
+			return true;
+		}
+
+		return $sanitized;
+	}
 }

includes/validation/class-amp-validation-manager.php

@@ -185,7 +185,7 @@ public static function init( $args = [] ) {
 			$args
 		);
 
-		self::$should_locate_sources = $args['should_locate_sources'];
+		self::$should_locate_sources = $args['should_locate_sources'] && ! AMP_Debug::has_flag( AMP_Debug::PREVENT_REDIRECT_TO_NON_AMP_QUERY_VAR );
 
 		AMP_Validated_URL_Post_Type::register();
 		AMP_Validation_Error_Taxonomy::register();
@@ -485,12 +485,15 @@ public static function add_admin_bar_menu_items( $wp_admin_bar ) {
 		 */
 		if ( $is_single_version_available ) {
 			$wp_admin_bar->add_node( $validate_item );
+			self::add_debugging_option_nodes( $wp_admin_bar, $amp_url );
 		} elseif ( ! is_amp_endpoint() ) {
 			$wp_admin_bar->add_node( $link_item );
 			$wp_admin_bar->add_node( $validate_item );
+			self::add_debugging_option_nodes( $wp_admin_bar, $amp_url );
 		} else {
 			$wp_admin_bar->add_node( $validate_item );
 			$wp_admin_bar->add_node( $link_item );
+			self::add_debugging_option_nodes( $wp_admin_bar, $amp_url );
 		}
 
 		// Scrub the query var from the URL.
@@ -519,6 +522,50 @@ function() {
 		self::$amp_admin_bar_item_added = true;
 	}
 
+	/**
+	 * Adds the debugging option links to the admin bar.
+	 *
+	 * @param WP_Admin_Bar $wp_admin_bar The admin bar to add the nodes to.
+	 * @param string       $amp_url The URL of the AMP endpoint.
+	 */
+	public static function add_debugging_option_nodes( &$wp_admin_bar, $amp_url ) {
+		$parent_node_id = 'amp-debug';
+		$wp_admin_bar->add_node(
+			[
+				'parent' => 'amp',
+				'id'     => $parent_node_id,
+				'title'  => esc_html__( 'Debugging options', 'amp' ),
+			]
+		);
+
+		foreach ( AMP_Debug::get_all_query_vars() as $query_var => $title ) {
+			$wp_admin_bar->add_node(
+				[
+					'parent' => $parent_node_id,
+					'id'     => $query_var,
+					'title'  => self::get_debugging_option_title( $title, $query_var ),
+					'href'   => add_query_arg( AMP_Debug::AMP_FLAGS_QUERY_VAR, [ $query_var => 'true' ], $amp_url ),
+				]
+			);
+		}
+	}
+
+	/**
+	 * Gets the debugging option title.
+	 *
+	 * If the current URL has the debugging option query var present, the title starts with a 'check mark' emoji.
+	 * For example, if the URL has the 'Prevent redirect' query var present,
+	 * the title in the Admin Bar will be '☑ Prevent redirect'.
+	 *
+	 * @param string $title_text The title of the option, like 'Prevent redirect'.
+	 * @param string $query_var The query var of the option.
+	 * @return string The debugging option title, possible with a 'check mark' emoji at the beginning.
+	 */
+	public static function get_debugging_option_title( $title_text, $query_var ) {
+		$checkbox = AMP_Debug::has_flag( $query_var ) ? '☑' : '☐';
+		return sprintf( '<span class="amp-debug-option" style="font-family:Roboto,Oxygen-Sans,sans-serif;font-size:17px">%s</span> %s', $checkbox, esc_html( $title_text ) );
+	}
+
 	/**
 	 * Add hooks for doing determining sources for validation errors during preprocessing/sanitizing.
 	 */

tests/php/stubs.php

@@ -24,3 +24,22 @@ public function get_styles() {
 		return [ 'styles' ];
 	}
 }
+
+// Stub class for WP_Admin_Bar.
+class AMP_Test_WP_Admin_Bar {
+	/**
+	 * The nodes in the admin bar.
+	 *
+	 * @var array
+	 */
+	public $nodes = [];
+
+	/**
+	 * Adds a node to display in the admin bar.
+	 *
+	 * @param array $node The node to add.
+	 */
+	public function add_node( $node ) {
+		array_push( $this->nodes, $node );
+	}
+}