Force Standard mode when fetching scannable URLs in Wizard

assets/src/components/site-scan-context-provider/index.js

@@ -79,6 +79,7 @@ function siteScanReducer( state, action ) {
 				...state,
 				status: STATUS_REQUEST_SCANNABLE_URLS,
 				currentlyScannedUrlIndex: INITIAL_STATE.currentlyScannedUrlIndex,
+				forceStandardMode: action?.forceStandardMode ?? state.forceStandardMode,
 			};
 		}
 		case ACTION_SCANNABLE_URLS_FETCH: {
@@ -169,14 +170,12 @@ function siteScanReducer( state, action ) {
  * Context provider for site scanning.
  *
  * @param {Object}  props                             Component props.
- * @param {boolean} props.ampFirst                    Whether scanning should be done with Standard mode being forced.
  * @param {?any}    props.children                    Component children.
  * @param {boolean} props.fetchCachedValidationErrors Whether to fetch cached validation errors on mount.
  * @param {string}  props.scannableUrlsRestPath       The REST path for interacting with the scannable URL resources.
  * @param {string}  props.validateNonce               The AMP validate nonce.
  */
 export function SiteScanContextProvider( {
-	ampFirst = false,
 	children,
 	fetchCachedValidationErrors = false,
 	scannableUrlsRestPath,
@@ -193,10 +192,11 @@ export function SiteScanContextProvider( {
 	const {
 		cache,
 		currentlyScannedUrlIndex,
+		forceStandardMode,
 		scannableUrls,
 		status,
 	} = state;
-	const urlType = ampFirst || themeSupport === STANDARD ? 'url' : 'amp_url';
+	const urlType = forceStandardMode || themeSupport === STANDARD ? 'url' : 'amp_url';
 	const previewPermalink = scannableUrls?.[ 0 ]?.[ urlType ] ?? '';
 
 	/**
@@ -232,17 +232,9 @@ export function SiteScanContextProvider( {
 	/**
 	 * Preflight check.
 	 */
-	useEffect( () => {
-		if ( status ) {
-			return;
-		}
-
-		if ( ! validateNonce ) {
-			throw new Error( 'Invalid site scan configuration' );
-		}
-
-		dispatch( { type: ACTION_SCANNABLE_URLS_REQUEST } );
-	}, [ status, validateNonce ] );
+	if ( ! validateNonce ) {
+		throw new Error( 'Invalid site scan configuration' );
+	}
 
 	/**
 	 * This component sets state inside async functions. Use this ref to prevent
@@ -253,6 +245,13 @@ export function SiteScanContextProvider( {
 		hasUnmounted.current = true;
 	}, [] );
 
+	const fetchScannableUrls = useCallback( ( args = {} ) => {
+		dispatch( {
+			type: ACTION_SCANNABLE_URLS_REQUEST,
+			forceStandardMode: args?.forceStandardMode,
+		} );
+	}, [] );
+
 	const startSiteScan = useCallback( ( args = {} ) => {
 		dispatch( {
 			type: ACTION_SCAN_INITIALIZE,
@@ -271,9 +270,9 @@ export function SiteScanContextProvider( {
 	const previousDidSaveOptions = usePrevious( didSaveOptions );
 	useEffect( () => {
 		if ( ! previousDidSaveOptions && didSaveOptions ) {
-			dispatch( { type: ACTION_SCANNABLE_URLS_REQUEST } );
+			fetchScannableUrls();
 		}
-	}, [ didSaveOptions, previousDidSaveOptions ] );
+	}, [ didSaveOptions, fetchScannableUrls, previousDidSaveOptions ] );
 
 	/**
 	 * Fetch scannable URLs from the REST endpoint.
@@ -291,6 +290,7 @@ export function SiteScanContextProvider( {
 				const response = await apiFetch( {
 					path: addQueryArgs( scannableUrlsRestPath, {
 						_fields: fetchCachedValidationErrors ? [ ...fields, 'validation_errors', 'stale' ] : fields,
+						force_standard_mode: forceStandardMode ? 1 : undefined,
 					} ),
 				} );
 
@@ -306,7 +306,7 @@ export function SiteScanContextProvider( {
 				setAsyncError( e );
 			}
 		} )();
-	}, [ fetchCachedValidationErrors, scannableUrlsRestPath, setAsyncError, status ] );
+	}, [ fetchCachedValidationErrors, forceStandardMode, scannableUrlsRestPath, setAsyncError, status ] );
 
 	/**
 	 * Scan site URLs sequentially.
@@ -322,7 +322,7 @@ export function SiteScanContextProvider( {
 			try {
 				const url = scannableUrls[ currentlyScannedUrlIndex ][ urlType ];
 				const args = {
-					'amp-first': ampFirst || undefined,
+					'amp-first': forceStandardMode || undefined,
 					amp_validate: {
 						cache: cache || undefined,
 						nonce: validateNonce,
@@ -362,13 +362,14 @@ export function SiteScanContextProvider( {
 
 			dispatch( { type: ACTION_SCAN_NEXT_URL } );
 		} )();
-	}, [ ampFirst, cache, currentlyScannedUrlIndex, scannableUrls, setAsyncError, status, urlType, validateNonce ] );
+	}, [ cache, currentlyScannedUrlIndex, forceStandardMode, scannableUrls, setAsyncError, status, urlType, validateNonce ] );
 
 	return (
 		<SiteScan.Provider
 			value={ {
 				cancelSiteScan,
 				currentlyScannedUrlIndex,
+				fetchScannableUrls,
 				hasSiteScanResults,
 				isBusy: [ STATUS_IDLE, STATUS_IN_PROGRESS ].includes( status ),
 				isCancelled: status === STATUS_CANCELLED,
@@ -391,7 +392,6 @@ export function SiteScanContextProvider( {
 }
 
 SiteScanContextProvider.propTypes = {
-	ampFirst: PropTypes.bool,
 	children: PropTypes.any,
 	fetchCachedValidationErrors: PropTypes.bool,
 	scannableUrlsRestPath: PropTypes.string,

assets/src/onboarding-wizard/index.js

@@ -86,7 +86,6 @@ export function Providers( { children } ) {
 									>
 										<TemplateModeOverrideContextProvider>
 											<SiteScanContextProvider
-												ampFirst={ true }
 												scannableUrlsRestPath={ SCANNABLE_URLS_REST_PATH }
 												validateNonce={ VALIDATE_NONCE }
 											>

assets/src/onboarding-wizard/pages/done/index.js

@@ -22,6 +22,7 @@ import {
 import { Navigation } from '../../components/navigation-context-provider';
 import { Options } from '../../../components/options-context-provider';
 import { ReaderThemes } from '../../../components/reader-themes-context-provider';
+import { SiteScan } from '../../../components/site-scan-context-provider';
 import { User } from '../../../components/user-context-provider';
 import { IconLaptopToggles } from '../../../components/svg/icon-laptop-toggles';
 import { IconLaptopSearch } from '../../../components/svg/icon-laptop-search';
@@ -47,6 +48,7 @@ export function Done() {
 	const { didSaveDeveloperToolsOption, saveDeveloperToolsOption, savingDeveloperToolsOption } = useContext( User );
 	const { canGoForward, setCanGoForward } = useContext( Navigation );
 	const { downloadedTheme, downloadingTheme, downloadingThemeError } = useContext( ReaderThemes );
+	const { isFetchingScannableUrls } = useContext( SiteScan );
 	const {
 		hasPreview,
 		isPreviewingAMP,
@@ -83,7 +85,7 @@ export function Done() {
 		}
 	}, [ didSaveDeveloperToolsOption, savingDeveloperToolsOption, saveDeveloperToolsOption ] );
 
-	if ( savingOptions || savingDeveloperToolsOption || downloadingTheme || hasOptionsChanges ) {
+	if ( savingOptions || savingDeveloperToolsOption || downloadingTheme || hasOptionsChanges || isFetchingScannableUrls ) {
 		return <Saving />;
 	}
 

assets/src/onboarding-wizard/setup-wizard.js

@@ -16,6 +16,7 @@ import PropTypes from 'prop-types';
 import { Logo } from '../components/svg/logo';
 import { UnsavedChangesWarning } from '../components/unsaved-changes-warning';
 import { useWindowWidth } from '../utils/use-window-width';
+import { SiteScan } from '../components/site-scan-context-provider';
 import { Stepper } from './components/stepper';
 import { Nav, CloseLink } from './components/nav';
 import { Navigation } from './components/navigation-context-provider';
@@ -46,6 +47,12 @@ function PageComponentSideEffects( { children } ) {
 export function SetupWizard( { closeLink, finishLink, appRoot } ) {
 	const { isMobile } = useWindowWidth();
 	const { activePageIndex, currentPage: { title, PageComponent, showTitle }, moveBack, moveForward, pages } = useContext( Navigation );
+	const { fetchScannableUrls } = useContext( SiteScan );
+
+	// Fetch the AMP-first scannable URLs needed for the Site Scan step.
+	useEffect( () => {
+		fetchScannableUrls( { forceStandardMode: true } );
+	}, [ fetchScannableUrls ] );
 
 	const PageComponentWithSideEffects = useMemo( () => () => (
 		<PageComponentSideEffects>

assets/src/settings-page/index.js

@@ -95,7 +95,6 @@ function Providers( { children } ) {
 								<PluginsContextProvider hasErrorBoundary={ true }>
 									<ThemesContextProvider hasErrorBoundary={ true }>
 										<SiteScanContextProvider
-											ampFirst={ false }
 											fetchCachedValidationErrors={ true }
 											scannableUrlsRestPath={ SCANNABLE_URLS_REST_PATH }
 											validateNonce={ VALIDATE_NONCE }

assets/src/settings-page/site-scan.js

@@ -41,6 +41,7 @@ import useDelayedFlag from '../utils/use-delayed-flag';
 export function SiteScan( { onSiteScan } ) {
 	const {
 		cancelSiteScan,
+		fetchScannableUrls,
 		hasSiteScanResults,
 		isBusy,
 		isCancelled,
@@ -58,9 +59,13 @@ export function SiteScan( { onSiteScan } ) {
 	const hasSiteIssues = themesWithAmpIncompatibility.length > 0 || pluginsWithAmpIncompatibility.length > 0;
 
 	/**
-	 * Cancel scan when component unmounts.
+	 * Fetch scannable URLs on mount; cancel site scan if the component unmounts.
 	 */
-	useEffect( () => () => cancelSiteScan(), [ cancelSiteScan ] );
+	useEffect( () => {
+		fetchScannableUrls();
+
+		return cancelSiteScan;
+	}, [ cancelSiteScan, fetchScannableUrls ] );
 
 	/**
 	 * Delay the `isCompleted` flag so that the progress bar stays at 100% for a

src/Admin/OnboardingWizardSubmenuPage.php

@@ -289,8 +289,10 @@ protected function add_preload_rest_paths() {
 			'/amp/v1/options',
 			'/amp/v1/reader-themes',
 			add_query_arg(
-				'_fields',
-				[ 'url', 'amp_url', 'type', 'label' ],
+				[
+					'_fields'             => [ 'url', 'amp_url', 'type', 'label' ],
+					'force_standard_mode' => 1,
+				],
 				'/amp/v1/scannable-urls'
 			),
 			'/wp/v2/plugins',

src/Validation/ScannableURLsRestController.php

@@ -8,11 +8,14 @@
 
 namespace AmpProject\AmpWP\Validation;
 
+use AMP_Options_Manager;
+use AMP_Theme_Support;
 use AMP_Validated_URL_Post_Type;
 use AMP_Validation_Manager;
 use AmpProject\AmpWP\Infrastructure\Delayed;
 use AmpProject\AmpWP\Infrastructure\Registerable;
 use AmpProject\AmpWP\Infrastructure\Service;
+use AmpProject\AmpWP\Option;
 use AmpProject\AmpWP\PairedRouting;
 use WP_Error;
 use WP_Post;
@@ -77,7 +80,14 @@ public function register() {
 					'methods'             => WP_REST_Server::READABLE,
 					'callback'            => [ $this, 'get_items' ],
 					'permission_callback' => [ $this, 'get_items_permissions_check' ],
-					'args'                => [],
+					'args'                => [
+						'force_standard_mode' => [
+							'description' => __( 'Indicates whether to force Standard template mode.', 'amp' ),
+							'type'        => 'boolean',
+							'required'    => false,
+							'default'     => false,
+						],
+					],
 				],
 				'schema' => [ $this, 'get_public_item_schema' ],
 			]
@@ -112,6 +122,19 @@ public function get_items_permissions_check( $request ) {
 	 * @return WP_REST_Response|WP_Error Response object on success, or WP_Error object on failure.
 	 */
 	public function get_items( $request ) { // phpcs:ignore VariableAnalysis.CodeAnalysis.VariableAnalysis.UnusedVariable
+		// Allow query parameter to force a response to be served with Standard mode (AMP-first). This is used as
+		// part of Site Scanning in order to determine if the primary theme is suitable for serving AMP.
+		if ( ! amp_is_canonical() && $request->get_param( 'force_standard_mode' ) ) {
+			add_filter(
+				'option_' . AMP_Options_Manager::OPTION_NAME,
+				function ( $options ) {
+					$options[ Option::THEME_SUPPORT ] = AMP_Theme_Support::STANDARD_MODE_SLUG;
+
+					return $options;
+				}
+			);
+		}
+
 		return rest_ensure_response(
 			array_map(
 				function ( $item ) use ( $request ) {