Add initial canonical AMP support

amp.php

@@ -127,13 +127,25 @@ function amp_force_query_var_value( $query_vars ) {
  * @return void
  */
 function amp_maybe_add_actions() {
-	if ( amp_is_canonical() || ! is_singular() || is_feed() ) {
+
+	// Add hooks for when a themes that support AMP.
+	if ( current_theme_supports( 'amp' ) ) {
+		if ( amp_is_canonical() || is_amp_endpoint() ) {
+			AMP_Theme_Support::register_hooks();
+		} else {
+			AMP_Frontend_Actions::register_hooks();
+		}
+		return;
+	}
+
+	// The remaining logic here is for paired mode running in themes that don't support AMP, the template system in AMP<=0.6.
+	if ( ! is_singular() || is_feed() ) {
 		return;
 	}
 
 	$is_amp_endpoint = is_amp_endpoint();
 
-	// Cannot use `get_queried_object` before canonical redirect; see https://core.trac.wordpress.org/ticket/35344
+	// Cannot use `get_queried_object` before canonical redirect; see <https://core.trac.wordpress.org/ticket/35344>.
 	global $wp_query;
 	$post = $wp_query->post;
 

composer.json

@@ -4,5 +4,10 @@
     "homepage": "https://github.com/Automattic/amp-wp",
     "type": "wordpress-plugin",
     "license": "GPL-2.0",
-    "version": "0.7.0"
+    "version": "0.7.0",
+    "require-dev": {
+        "wp-coding-standards/wpcs": "^0.14.0",
+        "dealerdirect/phpcodesniffer-composer-installer": "^0.4.4",
+        "wimg/php-compatibility": "^8.1"
+    }
 }

includes/actions/class-amp-frontend-actions.php

@@ -8,7 +8,7 @@
 /**
  * Class AMP_Frontend_Actions
  *
- * Callbacks for adding AMP-related things to the main theme
+ * Callbacks for adding AMP-related things to the main theme in non-canonical mode theme.
  */
 class AMP_Frontend_Actions {
 
@@ -26,7 +26,38 @@ public static function add_canonical() {
 		if ( false === apply_filters( 'add_canonical_link', true ) ) {
 			return;
 		}
-		$amp_url = amp_get_permalink( get_queried_object_id() );
-		printf( '<link rel="amphtml" href="%s" />', esc_url( $amp_url ) );
+		$amp_url = self::get_current_amphtml_url();
+		if ( ! empty( $amp_url ) ) {
+			printf( '<link rel="amphtml" href="%s" />', esc_url( $amp_url ) );
+		}
+	}
+
+	/**
+	 * Get the amphtml URL for the current request.
+	 *
+	 * @todo Put this function in includes/amp-helper-functions.php?
+	 * @return string|null URL or null if AMP version is not available.
+	 */
+	public static function get_current_amphtml_url() {
+		if ( is_singular() ) {
+			return amp_get_permalink( get_queried_object_id() );
+		}
+
+		// @todo Get callback from get_theme_support( 'amp' ) to determine whether AMP is allowed for current request. See <https://github.com/Automattic/amp-wp/issues/849>.
+		if ( ! current_theme_supports( 'amp' ) ) {
+			return null;
+		}
+
+		$amp_url  = '';
+		$home_url = wp_parse_url( home_url() );
+		if ( isset( $home_url['scheme'] ) ) {
+			$amp_url .= $home_url['scheme'] . ':';
+		}
+		$amp_url .= '//' . $home_url['host'];
+		if ( ! empty( $home_url['port'] ) ) {
+			$amp_url .= ':' . $home_url['port'];
+		}
+		$amp_url .= esc_url_raw( wp_unslash( $_SERVER['REQUEST_URI'] ) );
+		return add_query_arg( AMP_QUERY_VAR, '', $amp_url );
 	}
 }

includes/actions/class-amp-paired-post-actions.php

@@ -84,9 +84,7 @@ public static function add_fonts( $amp_template ) {
 	 * @param AMP_Post_Template $amp_template Template.
 	 */
 	public static function add_boilerplate_css( $amp_template ) {
-		?>
-		<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style><noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>
-		<?php
+		amp_print_boilerplate_code();
 	}
 
 	/**

includes/amp-helper-functions.php

@@ -90,3 +90,13 @@ function is_amp_endpoint() {
 function amp_get_asset_url( $file ) {
 	return plugins_url( sprintf( 'assets/%s', $file ), AMP__FILE__ );
 }
+
+/**
+ * Print AMP boilerplate code.
+ *
+ * @link https://www.ampproject.org/docs/reference/spec#boilerplate
+ */
+function amp_print_boilerplate_code() {
+	echo '<style amp-boilerplate>body{-webkit-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-moz-animation:-amp-start 8s steps(1,end) 0s 1 normal both;-ms-animation:-amp-start 8s steps(1,end) 0s 1 normal both;animation:-amp-start 8s steps(1,end) 0s 1 normal both}@-webkit-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-moz-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-ms-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@-o-keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}@keyframes -amp-start{from{visibility:hidden}to{visibility:visible}}</style>';
+	echo '<noscript><style amp-boilerplate>body{-webkit-animation:none;-moz-animation:none;-ms-animation:none;animation:none}</style></noscript>';
+}

includes/class-amp-autoloader.php

@@ -32,6 +32,7 @@ class AMP_Autoloader {
 		'AMP_Actions'                                 => 'includes/actions/class-amp-actions',
 		'AMP_Frontend_Actions'                        => 'includes/actions/class-amp-frontend-actions',
 		'AMP_Paired_Post_Actions'                     => 'includes/actions/class-amp-paired-post-actions',
+		'AMP_Theme_Support'                           => 'includes/class-amp-theme-support',
 		'AMP_Template_Customizer'                     => 'includes/admin/class-amp-customizer',
 		'AMP_Post_Meta_Box'                           => 'includes/admin/class-amp-post-meta-box',
 		'AMP_Post_Type_Support'                       => 'includes/class-amp-post-type-support',

includes/class-amp-theme-support.php

@@ -0,0 +1,229 @@
+<?php
+/**
+ * Class AMP_Theme_Support
+ *
+ * @package AMP
+ */
+
+/**
+ * Class AMP_Theme_Support
+ *
+ * Callbacks for adding AMP-related things when theme support is added.
+ */
+class AMP_Theme_Support {
+
+	const COMPONENT_SCRIPTS_PLACEHOLDER = '<!--AMP_COMPONENT_SCRIPTS_PLACEHOLDER-->';
+
+	/**
+	 * Register hooks.
+	 */
+	public static function register_hooks() {
+
+		// Remove core actions which are invalid AMP.
+		remove_action( 'wp_head', 'locale_stylesheet' );
+		remove_action( 'wp_head', 'print_emoji_detection_script', 7 );
+		remove_action( 'wp_head', 'wp_print_styles', 8 );
+		remove_action( 'wp_head', 'wp_print_head_scripts', 9 );
+		remove_action( 'wp_head', 'wp_custom_css_cb', 101 );
+		remove_action( 'wp_footer', 'wp_print_footer_scripts', 20 );
+		remove_action( 'wp_print_styles', 'print_emoji_styles' );
+
+		// Replace core's canonical link functionality with one that outputs links for non-singular queries as well. See WP Core #18660.
+		remove_action( 'wp_head', 'rel_canonical' );
+		add_action( 'wp_head', array( __CLASS__, 'add_canonical_link' ), 1 );
+
+		// @todo Add add_schemaorg_metadata(), add_analytics_data(), etc.
+		// Add additional markup required by AMP <https://www.ampproject.org/docs/reference/spec#required-markup>.
+		add_action( 'wp_head', array( __CLASS__, 'add_meta_charset' ), 0 );
+		add_action( 'wp_head', array( __CLASS__, 'add_meta_viewport' ), 2 );
+		add_action( 'wp_head', 'amp_print_boilerplate_code', 3 );
+		add_action( 'wp_head', array( __CLASS__, 'add_scripts' ), 4 );
+		add_action( 'wp_head', array( __CLASS__, 'add_styles' ), 5 );
+		add_action( 'wp_head', array( __CLASS__, 'add_meta_generator' ), 6 );
+
+		/*
+		 * Disable admin bar because admin-bar.css (28K) and Dashicons (48K) alone
+		 * combine to surpass the 50K limit imposed for the amp-custom style.
+		 */
+		add_filter( 'show_admin_bar', '__return_false', 100 );
+
+		// Start output buffering at very low priority for sake of plugins and themes that use template_redirect instead of template_include.
+		add_action( 'template_redirect', array( __CLASS__, 'start_output_buffering' ), 0 );
+
+		// @todo Add output buffering.
+		// @todo Add character conversion.
+	}
+
+	/**
+	 * Print meta charset tag.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#chrs
+	 */
+	public static function add_meta_charset() {
+		echo '<meta charset="utf-8">';
+	}
+
+	/**
+	 * Print meta charset tag.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#vprt
+	 */
+	public static function add_meta_viewport() {
+		echo '<meta name="viewport" content="width=device-width,minimum-scale=1">';
+	}
+
+	/**
+	 * Print AMP script and placeholder for others.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#scrpt
+	 */
+	public static function add_scripts() {
+		echo '<script async src="https://cdn.ampproject.org/v0.js"></script>'; // phpcs:ignore WordPress.WP.EnqueuedResources.NonEnqueuedScript
+
+		// Replaced after output buffering with all AMP component scripts.
+		echo self::COMPONENT_SCRIPTS_PLACEHOLDER; // phpcs:ignore WordPress.Security.EscapeOutput, WordPress.XSS.EscapeOutput
+	}
+
+	/**
+	 * Add canonical link.
+	 *
+	 * Replaces `rel_canonical()` which only outputs canonical URLs for singular posts and pages.
+	 * This can be removed once WP Core #18660 lands.
+	 *
+	 * @link https://www.ampproject.org/docs/reference/spec#canon.
+	 * @link https://core.trac.wordpress.org/ticket/18660
+	 *
+	 * @see rel_canonical()
+	 * @global WP $wp
+	 * @global WP_Rewrite $wp_rewrite
+	 */
+	public static function add_canonical_link() {
+		global $wp, $wp_rewrite;
+
+		$url = null;
+		if ( is_singular() ) {
+			$url = wp_get_canonical_url();
+		}
+
+		// For non-singular queries, make use of the request URI and public query vars to determine canonical URL.
+		if ( empty( $url ) ) {
+			$added_query_vars = $wp->query_vars;
+			if ( ! $wp_rewrite->permalink_structure || empty( $wp->request ) ) {
+				$url = home_url( '/' );
+			} else {
+				$url = home_url( user_trailingslashit( $wp->request ) );
+				parse_str( $wp->matched_query, $matched_query_vars );
+				foreach ( $wp->query_vars as $key => $value ) {
+
+					// Remove query vars that were matched in the rewrite rules for the request.
+					if ( isset( $matched_query_vars[ $key ] ) ) {
+						unset( $added_query_vars[ $key ] );
+					}
+				}
+			}
+		}
+
+		if ( ! empty( $added_query_vars ) ) {
+			$url = add_query_arg( $added_query_vars, $url );
+		}
+
+		if ( ! amp_is_canonical() ) {
+
+			// Strip endpoint.
+			$url = preg_replace( ':/' . preg_quote( AMP_QUERY_VAR, ':' ) . '(?=/?(\?|#|$)):', '', $url );
+
+			// Strip query var.
+			$url = remove_query_arg( AMP_QUERY_VAR, $url );
+		}
+
+		echo '<link rel="canonical" href="' . esc_url( $url ) . '">' . "\n";
+	}
+
+	/**
+	 * Print Custom AMP styles.
+	 *
+	 * @see wp_custom_css_cb()
+	 */
+	public static function add_styles() {
+		echo '<style amp-custom>';
+
+		// @todo Grab source of all enqueued styles and concatenate here?
+		// @todo Print contents of get_locale_stylesheet_uri()?
+		// @todo Allow this to be filtered after output buffering is complete so additional styles can be added by widgets and other components just-in-time?
+		$path = get_template_directory() . '/style.css'; // @todo Honor filter in get_stylesheet_directory_uri()? Style must be local.
+		$css  = file_get_contents( $path ); // phpcs:ignore WordPress.WP.AlternativeFunctions -- It's not a remote file.
+		echo wp_strip_all_tags( $css ); // WPCS: XSS OK.
+
+		// Implement AMP version of wp_custom_css_cb().
+		$custom_css = trim( wp_get_custom_css() );
+		if ( ! empty( $custom_css ) ) {
+			echo '/* start:wp_get_custom_css */';
+			echo wp_strip_all_tags( wp_get_custom_css() ); // WPCS: XSS OK.
+			echo '/* end:wp_get_custom_css */';
+		}
+		echo '</style>';
+	}
+
+	/**
+	 * Print AMP meta generator tag.
+	 */
+	public static function add_meta_generator() {
+		printf( '<meta name="generator" content="%s" />', esc_attr( 'AMP Plugin v' . AMP__VERSION ) );
+	}
+
+	/**
+	 * Determine required AMP scripts.
+	 *
+	 * @param string $html Output HTML.
+	 * @return string Scripts to inject into the HEAD.
+	 */
+	public static function get_required_amp_scripts( $html ) {
+
+		// @todo This should be integrated with the existing Sanitizer classes so that duplication is not done here.
+		$amp_scripts = array(
+			'amp-form' => array(
+				'pattern' => '#<(form|input)\b#i',
+				'source'  => 'https://cdn.ampproject.org/v0/amp-form-0.1.js',
+			),
+			// @todo Add more.
+		);
+
+		$scripts = '';
+		foreach ( $amp_scripts as $component => $props ) {
+			if ( preg_match( '#<(form|input)\b#i', $html ) ) {
+				$scripts .= sprintf(
+					'<script async custom-element="%s" src="%s"></script>', // phpcs:ignore WordPress.WP.EnqueuedResources, WordPress.XSS.EscapeOutput.OutputNotEscaped
+					$component,
+					$props['source']
+				);
+			}
+		}
+
+		return $scripts;
+	}
+
+	/**
+	 * Start output buffering.
+	 */
+	public static function start_output_buffering() {
+		ob_start( array( __CLASS__, 'finish_output_buffering' ) );
+	}
+
+	/**
+	 * Finish output buffering.
+	 *
+	 * @param string $output Buffered output.
+	 * @return string Finalized output.
+	 */
+	public static function finish_output_buffering( $output ) {
+		$output = preg_replace(
+			'#' . preg_quote( self::COMPONENT_SCRIPTS_PLACEHOLDER, '#' ) . '#',
+			self::get_required_amp_scripts( $output ),
+			$output,
+			1
+		);
+
+		// @todo Add more validation checking and potentially the whitelist sanitizer.
+		return $output;
+	}
+}

phpcs.xml

@@ -29,6 +29,12 @@
 		</properties>
 	</rule>
 
+	<!-- Include sniffs for PHP cross-version compatibility. -->
+	<config name="testVersion" value="5.2-99.0"/>
+	<rule ref="PHPCompatibility">
+		<exclude-pattern>bin/*</exclude-pattern>
+	</rule>
+
 	<arg value="s"/>
 	<arg name="extensions" value="php"/>
 	<file>.</file>