Allow AMP to be disabled for a request via noamp=available when user …

…can validate

Also add a "View with AMP disabled" link to the admin bar for such users to easily disable AMP for a URL when a site is in Standard mode without requiring them to switch the entire site to Transitional mode or to disable AMP for a given URL.

See #1294

includes/amp-helper-functions.php

@@ -406,7 +406,7 @@ function is_amp_available() {
 
 	// If redirected to this page because AMP is not available due to validation errors, prevent AMP from being available (if not AMP-first).
 	if (
-		! amp_is_canonical()
+		( ! amp_is_canonical() || AMP_Validation_Manager::has_cap() )
 		&&
 		( isset( $_GET[ QueryVars::NOAMP ] ) && QueryVars::NOAMP_AVAILABLE === $_GET[ QueryVars::NOAMP ] ) // phpcs:ignore WordPress.Security.NonceVerification.Recommended
 	) {

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

@@ -366,6 +366,9 @@ public static function add_admin_bar_menu_items( $wp_admin_bar ) {
 
 		$current_url = amp_get_current_url();
 		$non_amp_url = amp_remove_endpoint( $current_url );
+		if ( amp_is_canonical() ) {
+			$non_amp_url = add_query_arg( QueryVars::NOAMP, QueryVars::NOAMP_AVAILABLE, $non_amp_url );
+		}
 
 		$amp_url = remove_query_arg(
 			array_merge( wp_removable_query_args(), [ QueryVars::NOAMP ] ),
@@ -423,21 +426,23 @@ public static function add_admin_bar_menu_items( $wp_admin_bar ) {
 		$link_item = [
 			'parent' => 'amp',
 			'id'     => 'amp-view',
-			'title'  => esc_html( is_amp_endpoint() ? __( 'View non-AMP version', 'amp' ) : __( 'View AMP version', 'amp' ) ),
 			'href'   => esc_url( is_amp_endpoint() ? $non_amp_url : $amp_url ),
 		];
+		if ( amp_is_canonical() ) {
+			$link_item['title'] = esc_html__( 'View with AMP disabled', 'amp' );
+		} else {
+			$link_item['title'] = esc_html( is_amp_endpoint() ? __( 'View non-AMP version', 'amp' ) : __( 'View AMP version', 'amp' ) );
+		}
 
 		// Add top-level menu item. Note that this will correctly merge/amend any existing AMP nav menu item added in amp_add_admin_bar_view_link().
 		$wp_admin_bar->add_node( $parent );
 
-		if ( amp_is_canonical() ) {
+		if ( is_amp_endpoint() ) {
 			$wp_admin_bar->add_node( $validate_item );
-		} elseif ( ! is_amp_endpoint() ) {
 			$wp_admin_bar->add_node( $link_item );
-			$wp_admin_bar->add_node( $validate_item );
 		} else {
-			$wp_admin_bar->add_node( $validate_item );
 			$wp_admin_bar->add_node( $link_item );
+			$wp_admin_bar->add_node( $validate_item );
 		}
 
 		if ( AMP_Theme_Support::is_paired_available() && amp_is_dev_mode() ) { // @todo And user can manage_options.

tests/php/validation/test-class-amp-validation-manager.php

@@ -8,6 +8,7 @@
 // phpcs:disable Generic.Formatting.MultipleStatementAlignment.NotSameWarning
 
 use AmpProject\AmpWP\Option;
+use AmpProject\AmpWP\QueryVars;
 use AmpProject\AmpWP\Tests\AssertContainsCompatibility;
 use AmpProject\AmpWP\Tests\HandleValidation;
 use AmpProject\AmpWP\Tests\PrivateAccess;
@@ -330,7 +331,9 @@ public function test_add_admin_bar_menu_items() {
 		$node = $admin_bar->get_node( 'amp' );
 		$this->assertInternalType( 'object', $node );
 		$this->assertStringContains( 'action=amp_validate', $node->href );
-		$this->assertNull( $admin_bar->get_node( 'amp-view' ) );
+		$view_item = $admin_bar->get_node( 'amp-view' );
+		$this->assertInternalType( 'object', $view_item );
+		$this->assertEqualSets( [ QueryVars::NOAMP ], array_keys( $this->get_url_query_vars( $view_item->href ) ) );
 		$this->assertInternalType( 'object', $admin_bar->get_node( 'amp-validity' ) );
 
 		// Admin bar item available in paired mode.
@@ -357,13 +360,32 @@ public function test_add_admin_bar_menu_items() {
 		add_theme_support( AMP_Theme_Support::SLUG, [ AMP_Theme_Support::PAIRED_FLAG => true ] );
 		$admin_bar = new WP_Admin_Bar();
 		AMP_Validation_Manager::add_admin_bar_menu_items( $admin_bar );
-		$node = $admin_bar->get_node( 'amp' );
-		$this->assertInternalType( 'object', $node );
-		$this->assertStringEndsWith( '?amp', $node->href );
-		$this->assertInternalType( 'object', $admin_bar->get_node( 'amp-view' ) );
+		$root_node = $admin_bar->get_node( 'amp' );
+		$this->assertInternalType( 'object', $root_node );
+		$this->assertEqualSets( [ QueryVars::AMP ], array_keys( $this->get_url_query_vars( $root_node->href ) ) );
+
+		$view_item = $admin_bar->get_node( 'amp-view' );
+		$this->assertInternalType( 'object', $view_item );
+		$this->assertEqualSets( [ QueryVars::AMP ], array_keys( $this->get_url_query_vars( $view_item->href ) ) );
 		$this->assertInternalType( 'object', $admin_bar->get_node( 'amp-validity' ) );
 	}
 
+	/**
+	 * Get URL query vars.
+	 *
+	 * @param string $url URL.
+	 * @return array Query vars.
+	 */
+	private function get_url_query_vars( $url ) {
+		$query_string = wp_parse_url( $url, PHP_URL_QUERY );
+		if ( empty( $query_string ) ) {
+			return [];
+		}
+		$query_vars = [];
+		parse_str( $query_string, $query_vars );
+		return $query_vars;
+	}
+
 	/**
 	 * Test overrides.
 	 *