Filter the Post Format list to only formats that are supported

core-data/actions.js

@@ -64,3 +64,17 @@ export function receivePostTypes( postTypes ) {
 		postTypes: castArray( postTypes ),
 	};
 }
+
+/**
+ * Returns an action object used in signalling that the index has been received.
+ *
+ * @param {Object} index Index received.
+ *
+ * @return {Object} Action object.
+ */
+export function receiveThemeSupportsFromIndex( index ) {
+	return {
+		type: 'RECEIVE_THEME_SUPPORTS',
+		themeSupports: index.theme_supports,
+	};
+}

core-data/reducer.js

@@ -82,8 +82,29 @@ export function postTypes( state = {}, action ) {
 	return state;
 }
 
+/**
+ * Reducer managing theme supports data.
+ *
+ * @param {Object} state  Current state.
+ * @param {Object} action Dispatched action.
+ *
+ * @return {Object} Updated state.
+ */
+export function themeSupports( state = {}, action ) {
+	switch ( action.type ) {
+		case 'RECEIVE_THEME_SUPPORTS':
+			return {
+				...state,
+				...action.themeSupports,
+			};
+	}
+
+	return state;
+}
+
 export default combineReducers( {
 	terms,
 	media,
 	postTypes,
+	themeSupports,
 } );

core-data/resolvers.js

@@ -11,6 +11,7 @@ import {
 	receiveTerms,
 	receiveMedia,
 	receivePostTypes,
+	receiveThemeSupportsFromIndex,
 } from './actions';
 
 /**
@@ -44,3 +45,11 @@ export async function* getPostType( state, slug ) {
 	const postType = await apiRequest( { path: `/wp/v2/types/${ slug }?context=edit` } );
 	yield receivePostTypes( postType );
 }
+
+/**
+ * Requests theme supports data from the index.
+ */
+export async function* getThemeSupports() {
+	const index = await apiRequest( { path: '/' } );
+	yield receiveThemeSupportsFromIndex( index );
+}

core-data/selectors.js

@@ -69,3 +69,14 @@ export function getMedia( state, id ) {
 export function getPostType( state, slug ) {
 	return state.postTypes[ slug ];
 }
+
+/**
+ * Return theme suports data in the index.
+ *
+ * @param {Object} state Data state.
+ *
+ * @return {*}           Index data.
+ */
+export function getThemeSupports( state ) {
+	return state.themeSupports;
+}

editor/components/post-format/index.js

@@ -1,7 +1,7 @@
 /**
  * External dependencies
  */
-import { find } from 'lodash';
+import { find, get, includes, union } from 'lodash';
 
 /**
  * WordPress dependencies
@@ -30,9 +30,10 @@ const POST_FORMATS = [
 	{ id: 'chat', caption: __( 'Chat' ) },
 ];
 
-function PostFormat( { onUpdatePostFormat, postFormat = 'standard', suggestedFormat, instanceId } ) {
+function PostFormat( { onUpdatePostFormat, postFormat = 'standard', supportedFormats, suggestedFormat, instanceId } ) {
 	const postFormatSelectorId = 'post-format-selector-' + instanceId;
-	const suggestion = find( POST_FORMATS, ( format ) => format.id === suggestedFormat );
+	const formats = POST_FORMATS.filter( ( format ) => includes( supportedFormats, format.id ) );
+	const suggestion = find( formats, ( format ) => format.id === suggestedFormat );
 
 	// Disable reason: We need to change the value immiediately to show/hide the suggestion if needed
 
@@ -47,7 +48,7 @@ function PostFormat( { onUpdatePostFormat, postFormat = 'standard', suggestedFor
 						onChange={ ( event ) => onUpdatePostFormat( event.target.value ) }
 						id={ postFormatSelectorId }
 					>
-						{ POST_FORMATS.map( ( format ) => (
+						{ formats.map( ( format ) => (
 							<option key={ format.id } value={ format.id }>{ format.caption }</option>
 						) ) }
 					</select>
@@ -70,8 +71,14 @@ function PostFormat( { onUpdatePostFormat, postFormat = 'standard', suggestedFor
 export default compose( [
 	withSelect( ( select ) => {
 		const { getEditedPostAttribute, getSuggestedPostFormat } = select( 'core/editor' );
+		const postFormat = getEditedPostAttribute( 'format' );
+		const themeSupports = select( 'core' ).getThemeSupports();
+		// Ensure current format is always in the set.
+		// The current format may not be a format supported by the theme.
+		const supportedFormats = union( [ postFormat ], get( themeSupports, 'formats', [] ) );
 		return {
-			postFormat: getEditedPostAttribute( 'format' ),
+			postFormat,
+			supportedFormats,
 			suggestedFormat: getSuggestedPostFormat(),
 		};
 	} ),

lib/compat.php

@@ -216,6 +216,30 @@ function gutenberg_add_rest_nonce_to_heartbeat_response_headers( $response ) {
 
 add_filter( 'wp_refresh_nonces', 'gutenberg_add_rest_nonce_to_heartbeat_response_headers' );
 
+/**
+ * Ensure that the wp-json index contains the 'theme-supports' setting as
+ * part of its site info elements.
+ *
+ * @param WP_REST_Response $response WP REST API response of the wp-json index.
+ * @return WP_REST_Response Response that contains theme-supports.
+ */
+function gutenberg_ensure_wp_json_has_theme_supports( $response ) {
+	$site_info = $response->get_data();
+	if ( ! array_key_exists( 'theme_supports', $site_info ) ) {
+		$site_info['theme_supports'] = array();
+	}
+	if ( ! array_key_exists( 'formats', $site_info['theme_supports'] ) ) {
+		$formats = get_theme_support( 'post-formats' );
+		$formats = is_array( $formats ) ? array_values( $formats[0] ) : array();
+		$formats = array_merge( array( 'standard' ), $formats );
+
+		$site_info['theme_supports']['formats'] = $formats;
+	}
+	$response->set_data( $site_info );
+	return $response;
+}
+add_filter( 'rest_index', 'gutenberg_ensure_wp_json_has_theme_supports' );
+
 /**
  * As a substitute for the default content `wpautop` filter, applies autop
  * behavior only for posts where content does not contain blocks.
@@ -469,11 +493,12 @@ function gutenberg_get_post_type_viewable( $post_type ) {
 }
 
 /**
- * Adds the 'viewable' attribute to the REST API response of a post type.
+ * Adds extra fields to the REST API post type response.
  *
  * @see https://core.trac.wordpress.org/ticket/43739
+ * @see https://core.trac.wordpress.org/ticket/43817
  */
-function gutenberg_register_rest_api_post_type_viewable() {
+function gutenberg_register_rest_api_post_type_fields() {
 	register_rest_field( 'type',
 		'viewable',
 		array(
@@ -486,5 +511,6 @@ function gutenberg_register_rest_api_post_type_viewable() {
 			),
 		)
 	);
+
 }
-add_action( 'rest_api_init', 'gutenberg_register_rest_api_post_type_viewable' );
+add_action( 'rest_api_init', 'gutenberg_register_rest_api_post_type_fields' );

phpunit/class-gutenberg-rest-api-test.php

@@ -119,4 +119,16 @@ function test_viewable_field_without_context() {
 		$result   = $response->get_data();
 		$this->assertFalse( isset( $result['viewable'] ) );
 	}
+
+	/**
+	 * Should include relevant data in the 'theme_supports' key of index.
+	 */
+	function test_theme_supports_index() {
+		$request  = new WP_REST_Request( 'GET', '/' );
+		$response = rest_do_request( $request );
+		$result   = $response->get_data();
+		$this->assertTrue( isset( $result['theme_supports'] ) );
+		$this->assertTrue( isset( $result['theme_supports']['formats'] ) );
+		$this->assertTrue( in_array( 'standard', $result['theme_supports']['formats'] ) );
+	}
 }