Allow plugins to add new items to the "Add new" menu on the Site Editor

lib/compat/wordpress-6.2/site-editor.php

@@ -6,19 +6,30 @@
  */
 
 /**
- * Remove home template setting for WP 6.2.
+ * Remove home template setting and add filtered extraTemplatesTypes setting for WP 6.2.
  *
  * @param array                   $settings Existing block editor settings.
  * @param WP_Block_Editor_Context $context The current block editor context.
  * @return array
  */
-function gutenberg_site_editor_unset_homepage_setting( $settings, $context ) {
+function gutenberg_site_editor_update_settings( $settings, $context ) {
 	if ( isset( $context->post ) ) {
 		return $settings;
 	}
 
 	unset( $settings['__unstableHomeTemplate'] );
 
+	/**
+	 * Filters the list of extra templates.
+	 *
+	 * Template types added in this filter will show up under the `Add new` menu in the Site Editor.
+	 *
+	 * @since 6.2.0
+	 *
+	 * @param array $extra_template_types An array of template types, formatted as [ slug, title, description ] ].
+	 */
+	$settings['extraTemplateTypes'] = apply_filters( 'extra_template_types', array() );
+
 	return $settings;
 }
-add_filter( 'block_editor_settings_all', 'gutenberg_site_editor_unset_homepage_setting', 10, 2 );
+add_filter( 'block_editor_settings_all', 'gutenberg_site_editor_update_settings', 10, 2 );

packages/edit-site/src/components/add-new-template/new-template.js

@@ -42,6 +42,7 @@ import {
 	usePostTypeMenuItems,
 	useAuthorMenuItem,
 	usePostTypeArchiveMenuItems,
+	useExtraTemplateTypes,
 } from './utils';
 import AddCustomGenericTemplateModal from './add-custom-generic-template-modal';
 import TemplateActionsLoadingScreen from './template-actions-loading-screen';
@@ -277,6 +278,7 @@ function useMissingTemplates(
 			DEFAULT_TEMPLATE_SLUGS.includes( template.slug ) &&
 			! existingTemplateSlugs.includes( template.slug )
 	);
+	const extraTemplateTypes = useExtraTemplateTypes();
 	const onClickMenuItem = ( _entityForSuggestions ) => {
 		setShowCustomTemplateModal( true );
 		setEntityForSuggestions( _entityForSuggestions );
@@ -327,5 +329,13 @@ function useMissingTemplates(
 		...postTypesMenuItems,
 		...taxonomiesMenuItems,
 	];
-	return missingTemplates;
+
+	const missingTemplateSlugs = ( missingTemplates || [] ).map(
+		( { slug } ) => slug
+	);
+	const missingExtraTemplateTypes = ( extraTemplateTypes || [] ).filter(
+		( template ) => ! missingTemplateSlugs.includes( template.slug )
+	);
+
+	return [ ...missingTemplates, ...missingExtraTemplateTypes ];
 }

packages/edit-site/src/components/add-new-template/utils.js

@@ -59,6 +59,11 @@ export const useDefaultTemplateTypes = () => {
 		[]
 	);
 };
+export const useExtraTemplateTypes = () => {
+	return useSelect( ( select ) => {
+		return select( editorStore ).__experimentalGetExtraTemplateTypes();
+	}, [] );
+};
 
 const usePublicPostTypes = () => {
 	const postTypes = useSelect(

packages/edit-site/src/index.js

@@ -84,6 +84,7 @@ export function reinitializeEditor( target, settings ) {
 		dispatch( editorStore ).updateEditorSettings( {
 			defaultTemplateTypes: settings.defaultTemplateTypes,
 			defaultTemplatePartAreas: settings.defaultTemplatePartAreas,
+			extraTemplateTypes: settings.extraTemplateTypes,
 		} );
 	}
 

packages/editor/src/store/selectors.js

@@ -1549,6 +1549,17 @@ export function __experimentalGetDefaultTemplateTypes( state ) {
 	return getEditorSettings( state )?.defaultTemplateTypes;
 }
 
+/**
+ * Returns the extra template slugs.
+ *
+ * @param {Object} state Global application state.
+ *
+ * @return {Array} The template slugs.
+ */
+export function __experimentalGetExtraTemplateTypes( state ) {
+	return getEditorSettings( state )?.extraTemplateTypes;
+}
+
 /**
  * Returns the default template part areas.
  *