Add support for allowing a site subset to be native AMP

amp.php

@@ -272,28 +272,67 @@ function amp_correct_query_when_is_front_page( WP_Query $query ) {
 }
 
 /**
- * Whether this is in 'canonical mode.'
+ * Whether this is in 'canonical mode'.
  *
- * Themes can register support for this with `add_theme_support( 'amp' )`.
- * Then, this will change the plugin from 'paired mode,' and it won't use its own templates.
- * Nor output frontend markup like the 'rel' link. If the theme registers support for AMP with:
- * `add_theme_support( 'amp', array( 'template_dir' => 'my-amp-templates' ) )`
- * it will retain 'paired mode.
+ * Themes can register support for this with `add_theme_support( 'amp' )`:
  *
- * @return boolean Whether this is in AMP 'canonical mode'.
+ *      add_theme_support( 'amp' );
+ *
+ * This will serve templates in native AMP by default but the user would be able to change the template mode
+ * from native to paired in the admin. To force only native to be available, such as when you are using AMP components
+ * in your theme templates, do:
+ *
+ *      add_theme_support( 'amp', array(
+ *          'mode' => 'native',
+ *      ) );
+ *
+ * If you want to force AMP to always be served on a given template, you can use the templates_supported arg,
+ * for example to always serve the Category template in AMP:
+ *
+ *      add_theme_support( 'amp', array(
+ *          'templates_supported' => array(
+ *              'is_category' => true,
+ *          ),
+ *      ) );
+ *
+ * Or if you want to force AMP to be used on all templates:
+ *
+ *      add_theme_support( 'amp', array(
+ *          'templates_supported' => 'all',
+ *      ) );
+ *
+ * @see AMP_Theme_Support::read_theme_support()
+ * @return boolean Whether this is in AMP 'canonical' mode, that is whether it is native and there is not separate AMP URL current URL.
  */
 function amp_is_canonical() {
-	$support = get_theme_support( 'amp' );
-	if ( true === $support ) {
-		return true;
+	if ( ! current_theme_supports( 'amp' ) ) {
+		return false;
 	}
+
+	$mode    = 'native';
+	$support = get_theme_support( 'amp' );
 	if ( is_array( $support ) ) {
-		$args = array_shift( $support );
-		if ( empty( $args['template_dir'] ) ) {
-			return true;
+		$args    = array_shift( $support );
+		$support = AMP_Options_Manager::get_option( 'theme_support' );
+
+		// If support is optional, look at DB option if mode is not explicitly set in theme support.
+		if ( ! empty( $args['optional'] ) ) {
+			if ( 'disabled' === $support ) {
+				return false;
+			} elseif ( ! isset( $args['mode'] ) ) {
+				return 'native' === $support;
+			}
+		}
+
+		if ( isset( $args['mode'] ) ) {
+			$mode = $args['mode'];
+		} elseif ( 'disabled' !== $support ) {
+			$mode = $support; // Supplied via admin screen.
+		} elseif ( ! empty( $args['template_dir'] ) ) {
+			$mode = 'paired'; // If there is a template_dir, then paired mode is implied.
 		}
 	}
-	return false;
+	return 'native' === $mode;
 }
 
 /**
@@ -426,6 +465,7 @@ function _amp_bootstrap_customizer() {
 
 /**
  * Redirects the old AMP URL to the new AMP URL.
+ *
  * If post slug is updated the amp page with old post slug will be redirected to the updated url.
  *
  * @since 0.5

includes/admin/class-amp-editor-blocks.php

@@ -43,6 +43,22 @@ public function init() {
 		if ( function_exists( 'gutenberg_init' ) ) {
 			add_action( 'enqueue_block_editor_assets', array( $this, 'enqueue_block_editor_assets' ) );
 			add_filter( 'wp_kses_allowed_html', array( $this, 'whitelist_block_atts_in_wp_kses_allowed_html' ), 10, 2 );
+
+			/*
+			 * Dirty AMP is required when a site is in native mode but not all templates are being served
+			 * as AMP. In particular, if a single post is using AMP-specific Gutenberg Blocks which make
+			 * use of AMP components, and the singular template is served as AMP but the blog page is not,
+			 * then the non-AMP blog page need to load the AMP runtime scripts so that the AMP components
+			 * in the posts displayed there will be rendered properly. This is only relevant on native AMP
+			 * sites because the AMP Gutenberg blocks are only made available in that mode; they are not
+			 * presented in the Gutenberg inserter in paired mode. In general, using AMP components in
+			 * non-AMP documents is still not officially supported, so it's occurrence is being minimized
+			 * as much as possible. For more, see <https://github.com/Automattic/amp-wp/issues/1192>.
+			 */
+			if ( amp_is_canonical() ) {
+				add_filter( 'the_content', array( $this, 'tally_content_requiring_amp_scripts' ) );
+				add_action( 'wp_print_footer_scripts', array( $this, 'print_dirty_amp_scripts' ) );
+			}
 		}
 	}
 
@@ -145,4 +161,32 @@ public function enqueue_block_editor_assets() {
 			) ) )
 		);
 	}
+
+	/**
+	 * Tally the AMP component scripts that are needed in a dirty AMP document.
+	 *
+	 * @param string $content Content.
+	 * @return string Content (unmodified).
+	 */
+	public function tally_content_requiring_amp_scripts( $content ) {
+		if ( ! is_amp_endpoint() ) {
+			$pattern = sprintf( '/<(%s)\b.*?>/s', join( '|', $this->amp_blocks ) );
+			if ( preg_match_all( $pattern, $content, $matches ) ) {
+				$this->content_required_amp_scripts = array_merge(
+					$this->content_required_amp_scripts,
+					$matches[1]
+				);
+			}
+		}
+		return $content;
+	}
+
+	/**
+	 * Print AMP scripts required for AMP components used in a non-AMP document (dirty AMP).
+	 */
+	public function print_dirty_amp_scripts() {
+		if ( ! is_amp_endpoint() && ! empty( $this->content_required_amp_scripts ) ) {
+			wp_scripts()->do_items( $this->content_required_amp_scripts );
+		}
+	}
 }

includes/admin/class-amp-post-meta-box.php

@@ -143,12 +143,20 @@ public function enqueue_admin_assets() {
 			array( 'jquery' ),
 			AMP__VERSION
 		);
+
+		if ( current_theme_supports( 'amp' ) ) {
+			$availability   = AMP_Theme_Support::get_template_availability( $post );
+			$support_errors = $availability['errors'];
+		} else {
+			$support_errors = AMP_Post_Type_Support::get_support_errors( $post );
+		}
+
 		wp_add_inline_script( self::ASSETS_HANDLE, sprintf( 'ampPostMetaBox.boot( %s );',
 			wp_json_encode( array(
 				'previewLink'     => esc_url_raw( add_query_arg( amp_get_slug(), '', get_preview_post_link( $post ) ) ),
 				'canonical'       => amp_is_canonical(),
-				'enabled'         => post_supports_amp( $post ),
-				'canSupport'      => count( AMP_Post_Type_Support::get_support_errors( $post ) ) === 0,
+				'enabled'         => empty( $support_errors ),
+				'canSupport'      => 0 === count( array_diff( $support_errors, array( 'post-status-disabled' ) ) ),
 				'statusInputName' => self::STATUS_INPUT_NAME,
 				'l10n'            => array(
 					'ampPreviewBtnLabel' => __( 'Preview changes in AMP (opens in new window)', 'amp' ),
@@ -170,23 +178,37 @@ public function render_status( $post ) {
 			is_post_type_viewable( $post->post_type )
 			&&
 			current_user_can( 'edit_post', $post->ID )
-			&&
-			! amp_is_canonical()
 		);
 
 		if ( true !== $verify ) {
 			return;
 		}
 
-		$errors = AMP_Post_Type_Support::get_support_errors( $post );
-		$status = post_supports_amp( $post ) ? self::ENABLED_STATUS : self::DISABLED_STATUS;
+		/*
+		 * When theme support is present then theme templates can be served in AMP and we check first if the template is available.
+		 * Checking for template availability will include a check for get_support_errors. Otherwise, if theme support is not present
+		 * then we just check get_support_errors.
+		 */
+		if ( current_theme_supports( 'amp' ) ) {
+			$availability = AMP_Theme_Support::get_template_availability( $post );
+			$status       = $availability['supported'] ? self::ENABLED_STATUS : self::DISABLED_STATUS;
+			$errors       = array_diff( $availability['errors'], array( 'post-status-disabled' ) ); // Subtract the status which the metabox will allow to be toggled.
+			if ( true === $availability['immutable'] ) {
+				$errors[] = 'status_immutable';
+			}
+		} else {
+			$errors = AMP_Post_Type_Support::get_support_errors( $post );
+			$status = empty( $errors ) ? self::ENABLED_STATUS : self::DISABLED_STATUS;
+			$errors = array_diff( $errors, array( 'post-status-disabled' ) ); // Subtract the status which the metabox will allow to be toggled.
+		}
+
 		$labels = array(
 			'enabled'  => __( 'Enabled', 'amp' ),
 			'disabled' => __( 'Disabled', 'amp' ),
 		);
 
 		// The preceding variables are used inside the following amp-status.php template.
-		include_once AMP__DIR__ . '/templates/admin/amp-status.php';
+		include AMP__DIR__ . '/templates/admin/amp-status.php';
 	}
 
 	/**

includes/amp-helper-functions.php

@@ -123,6 +123,9 @@ function amp_get_permalink( $post_id ) {
 			||
 			// If the post type is hierarchical then the /amp/ endpoint isn't available.
 			is_post_type_hierarchical( get_post_type( $post_id ) )
+			||
+			// Attachment pages don't accept the /amp/ endpoint.
+			'attachment' === get_post_type( $post_id )
 		);
 		if ( $use_query_var ) {
 			$amp_url = add_query_arg( amp_get_slug(), '', $permalink );
@@ -239,61 +242,20 @@ function amp_add_amphtml_link() {
  * @see   AMP_Post_Type_Support::get_support_errors()
  *
  * @param WP_Post $post Post.
- *
  * @return bool Whether the post supports AMP.
  */
 function post_supports_amp( $post ) {
-	if ( amp_is_canonical() ) {
-		return true;
-	}
-
-	$errors = AMP_Post_Type_Support::get_support_errors( $post );
-
-	// Return false if an error is found.
-	if ( ! empty( $errors ) ) {
-		return false;
-	}
-
-	switch ( get_post_meta( $post->ID, AMP_Post_Meta_Box::STATUS_POST_META_KEY, true ) ) {
-		case AMP_Post_Meta_Box::ENABLED_STATUS:
-			return true;
-
-		case AMP_Post_Meta_Box::DISABLED_STATUS:
-			return false;
-
-		// Disabled by default for custom page templates, page on front and page for posts.
-		default:
-			$enabled = (
-				! (bool) get_page_template_slug( $post )
-				&&
-				! (
-					'page' === $post->post_type
-					&&
-					'page' === get_option( 'show_on_front' )
-					&&
-					in_array( (int) $post->ID, array(
-						(int) get_option( 'page_on_front' ),
-						(int) get_option( 'page_for_posts' ),
-					), true )
-				)
-			);
-
-			/**
-			 * Filters whether default AMP status should be enabled or not.
-			 *
-			 * @since 0.6
-			 *
-			 * @param string  $status Status.
-			 * @param WP_Post $post   Post.
-			 */
-			return apply_filters( 'amp_post_status_default_enabled', $enabled, $post );
-	}
+	return 0 === count( AMP_Post_Type_Support::get_support_errors( $post ) );
 }
 
 /**
- * Are we currently on an AMP URL?
+ * Determine whether the current response being served as AMP.
  *
- * @since 1.0 This function can be called before the `parse_query` action because the 'amp' query var is specifically and exclusively used when 'amp' theme support is added.
+ * This function cannot be called before the parse_query action because it needs to be able
+ * to determine the queried object is able to be served as AMP. If 'amp' theme support is not
+ * present, this function returns true just if the query var is present. If theme support is
+ * present, then it returns true in paired mode if an AMP template is available and the query
+ * var is present, or else in native mode if just the template is available.
  *
  * @return bool Whether it is the AMP endpoint.
  */
@@ -302,17 +264,29 @@ function is_amp_endpoint() {
 		return false;
 	}
 
-	// When 'amp' theme support is (or will be added) then these are the conditions that are key to be checked.
-	if ( amp_is_canonical() || isset( $_GET[ amp_get_slug() ] ) ) { // WPCS: CSRF OK.
-		return true;
+	$did_parse_query = did_action( 'parse_query' );
+
+	if ( ! $did_parse_query ) {
+		_doing_it_wrong( __FUNCTION__, sprintf( esc_html__( "is_amp_endpoint() was called before the 'parse_query' hook was called. This function will always return 'false' before the 'parse_query' hook is called.", 'amp' ) ), '0.4.2' );
 	}
 
-	// Condition for non-theme support when /amp/ endpoint is used.
-	if ( false !== get_query_var( amp_get_slug(), false ) ) {
-		return true;
+	$has_amp_query_var = (
+		isset( $_GET[ amp_get_slug() ] ) // WPCS: CSRF OK.
+		||
+		false !== get_query_var( amp_get_slug(), false )
+	);
+
+	if ( ! current_theme_supports( 'amp' ) ) {
+		return $has_amp_query_var;
+	}
+
+	// When there is no query var and AMP is not canonical/native, then this is definitely not an AMP endpoint.
+	if ( ! $has_amp_query_var && ! amp_is_canonical() ) {
+		return false;
 	}
 
-	return false;
+	$availability = AMP_Theme_Support::get_template_availability();
+	return amp_is_canonical() ? $availability['supported'] : ( $has_amp_query_var && $availability['supported'] );
 }
 
 /**