Proof of concept

packages/edit-site/src/components/sidebar-navigation-screen-navigation-menu/index.js

@@ -1,6 +1,9 @@
 /**
  * WordPress dependencies
  */
+/**
+ * Internal dependencies
+ */
 import { useEntityRecord, store as coreStore } from '@wordpress/core-data';
 import {
 	__experimentalUseNavigator as useNavigator,
@@ -9,7 +12,6 @@ import {
 import { __, sprintf } from '@wordpress/i18n';
 import { useSelect, useDispatch } from '@wordpress/data';
 import { decodeEntities } from '@wordpress/html-entities';
-
 import { store as noticesStore } from '@wordpress/notices';
 
 /**
@@ -19,8 +21,6 @@ import { SidebarNavigationScreenWrapper } from '../sidebar-navigation-screen-nav
 import ScreenNavigationMoreMenu from './more-menu';
 import NavigationMenuEditor from './navigation-menu-editor';
 
-export const noop = () => {};
-
 export default function SidebarNavigationScreenNavigationMenu() {
 	const {
 		deleteEntityRecord,
@@ -229,7 +229,7 @@ export default function SidebarNavigationScreenNavigationMenu() {
 				'Navigation menus are a curated collection of blocks that allow visitors to get around your site.'
 			) }
 		>
-			<NavigationMenuEditor navigationMenu={ navigationMenu } />
+			<NavigationMenuEditor navigationMenuId={ navigationMenu?.id } />
 		</SidebarNavigationScreenWrapper>
 	);
 }

packages/edit-site/src/components/sidebar-navigation-screen-navigation-menu/navigation-menu-editor.js

@@ -6,7 +6,6 @@ import { useSelect } from '@wordpress/data';
 import { BlockEditorProvider } from '@wordpress/block-editor';
 import { createBlock } from '@wordpress/blocks';
 import { privateApis as routerPrivateApis } from '@wordpress/router';
-
 /**
  * Internal dependencies
  */
@@ -17,11 +16,12 @@ import {
 	currentlyPreviewingTheme,
 } from '../../utils/is-previewing-theme';
 import NavigationMenuContent from '../sidebar-navigation-screen-navigation-menus/navigation-menu-content';
-import { noop } from '.';
 
 const { useHistory } = unlock( routerPrivateApis );
 
-export default function NavigationMenuEditor( { navigationMenu } ) {
+const noop = () => {};
+
+export default function NavigationMenuEditor( { navigationMenuId } ) {
 	const history = useHistory();
 
 	const onSelect = useCallback(
@@ -63,16 +63,14 @@ export default function NavigationMenuEditor( { navigationMenu } ) {
 	}, [] );
 
 	const blocks = useMemo( () => {
-		if ( ! navigationMenu ) {
+		if ( ! navigationMenuId ) {
 			return [];
 		}
 
-		return [
-			createBlock( 'core/navigation', { ref: navigationMenu?.id } ),
-		];
-	}, [ navigationMenu ] );
+		return [ createBlock( 'core/navigation', { ref: navigationMenuId } ) ];
+	}, [ navigationMenuId ] );
 
-	if ( ! navigationMenu || ! blocks?.length ) {
+	if ( ! navigationMenuId || ! blocks?.length ) {
 		return null;
 	}
 

packages/edit-site/src/components/sidebar-navigation-screen-template-part/index.js

@@ -20,11 +20,14 @@ import { store as editSiteStore } from '../../store';
 import SidebarButton from '../sidebar-button';
 import { useAddedBy } from '../list/added-by';
 
+import TemplatePartNavigationMenus from './template-part-navigation-menus';
+
 function useTemplateTitleAndDescription( postType, postId ) {
 	const { getDescription, getTitle, record } = useEditedEntityRecord(
 		postType,
 		postId
 	);
+
 	const currentTheme = useSelect(
 		( select ) => select( coreStore ).getCurrentTheme(),
 		[]
@@ -82,11 +85,25 @@ export default function SidebarNavigationScreenTemplatePart() {
 	const { params } = useNavigator();
 	const { postType, postId } = params;
 	const { setCanvasMode } = unlock( useDispatch( editSiteStore ) );
+
+	const { record } = useEditedEntityRecord( postType, postId );
+
 	const { title, description } = useTemplateTitleAndDescription(
 		postType,
 		postId
 	);
 
+	const navigationBlocks = getBlocksFromBlocks(
+		'core/navigation',
+		record?.blocks
+	);
+
+	// Get a list of the navigation menu ids from the navigation blocks'
+	// ref attribute.
+	const navigationMenuIds = navigationBlocks?.map( ( block ) => {
+		return block.attributes.ref;
+	} );
+
 	return (
 		<SidebarNavigationScreen
 			title={ title }
@@ -98,6 +115,46 @@ export default function SidebarNavigationScreenTemplatePart() {
 				/>
 			}
 			description={ description }
+			content={
+				<TemplatePartNavigationMenus menus={ navigationMenuIds } />
+			}
 		/>
 	);
 }
+
+/**
+ * Retrieves a list of specific blocks from a given set of blocks.
+ *
+ * @param {string} targetBlock the name of the block to find.
+ * @param {Array}  blocks      a list of blocks from the template part entity.
+ * @return {Array} a list of any navigation blocks found in the blocks.
+ */
+function getBlocksFromBlocks( targetBlock, blocks ) {
+	if ( ! targetBlock || ! blocks?.length ) return [];
+
+	const findInBlocks = ( _blocks ) => {
+		if ( ! _blocks ) {
+			return [];
+		}
+
+		const navigationBlocks = [];
+
+		for ( const block of _blocks ) {
+			if ( block.name === targetBlock ) {
+				navigationBlocks.push( block );
+			}
+
+			if ( block?.innerBlocks ) {
+				const innerNavigationBlocks = findInBlocks( block.innerBlocks );
+
+				if ( innerNavigationBlocks.length ) {
+					navigationBlocks.push( ...innerNavigationBlocks );
+				}
+			}
+		}
+
+		return navigationBlocks;
+	};
+
+	return findInBlocks( blocks );
+}

packages/edit-site/src/components/sidebar-navigation-screen-template-part/style.scss

@@ -0,0 +1,3 @@
+.edit-site-sidebar-navigation-screen-template-part-navigation-menu__title.components-heading {
+	margin-bottom: $grid-unit-10;
+}

packages/edit-site/src/components/sidebar-navigation-screen-template-part/template-part-navigation-menu-list-item.js

@@ -0,0 +1,26 @@
+/**
+ * WordPress dependencies
+ */
+import { useEntityProp } from '@wordpress/core-data';
+/**
+ * Internal dependencies
+ */
+import SidebarNavigationItem from '../sidebar-navigation-item';
+import { useLink } from '../routes/link';
+
+export default function TemplatePartNavigationMenuListItem( { id } ) {
+	const [ title ] = useEntityProp( 'postType', 'wp_navigation', 'title', id );
+
+	const linkInfo = useLink( {
+		postId: id,
+		postType: 'wp_navigation',
+	} );
+
+	if ( ! id ) return null;
+
+	return (
+		<SidebarNavigationItem withChevron { ...linkInfo }>
+			{ title }
+		</SidebarNavigationItem>
+	);
+}

packages/edit-site/src/components/sidebar-navigation-screen-template-part/template-part-navigation-menu-list.js

@@ -0,0 +1,21 @@
+/**
+ * WordPress dependencies
+ */
+import { __experimentalItemGroup as ItemGroup } from '@wordpress/components';
+/**
+ * Internal dependencies
+ */
+import TemplatePartNavigationMenuListItem from './template-part-navigation-menu-list-item';
+
+export default function TemplatePartNavigationMenuList( { menus } ) {
+	return (
+		<ItemGroup className="edit-site-sidebar-navigation-screen-template-part-navigation-menu-list">
+			{ menus.map( ( menuId ) => (
+				<TemplatePartNavigationMenuListItem
+					key={ menuId }
+					id={ menuId }
+				/>
+			) ) }
+		</ItemGroup>
+	);
+}

packages/edit-site/src/components/sidebar-navigation-screen-template-part/template-part-navigation-menu.js

@@ -0,0 +1,29 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { __experimentalHeading as Heading } from '@wordpress/components';
+import { useEntityProp } from '@wordpress/core-data';
+/**
+ * Internal dependencies
+ */
+import NavigationMenuEditor from '../sidebar-navigation-screen-navigation-menu/navigation-menu-editor';
+
+export default function TemplatePartNavigationMenu( { id } ) {
+	const [ title ] = useEntityProp( 'postType', 'wp_navigation', 'title', id );
+
+	if ( ! id ) return null;
+
+	return (
+		<>
+			<Heading
+				className="edit-site-sidebar-navigation-screen-template-part-navigation-menu__title"
+				size="12"
+				upperCase={ true }
+			>
+				{ title || __( 'Navigation Menu' ) }
+			</Heading>
+			<NavigationMenuEditor navigationMenuId={ id } />
+		</>
+	);
+}

packages/edit-site/src/components/sidebar-navigation-screen-template-part/template-part-navigation-menus.js

@@ -0,0 +1,33 @@
+/**
+ * WordPress dependencies
+ */
+import { __ } from '@wordpress/i18n';
+import { __experimentalHeading as Heading } from '@wordpress/components';
+/**
+ * Internal dependencies
+ */
+import TemplatePartNavigationMenu from './template-part-navigation-menu';
+import TemplatePartNavigationMenuList from './template-part-navigation-menu-list';
+
+export default function TemplatePartNavigationMenus( { menus } ) {
+	if ( ! menus.length ) return null;
+
+	// if there is a single menu then render TemplatePartNavigationMenu
+	if ( menus.length === 1 ) {
+		return <TemplatePartNavigationMenu id={ menus[ 0 ] } />;
+	}
+
+	// if there are multiple menus then render TemplatePartNavigationMenuList
+	return (
+		<>
+			<Heading
+				className="edit-site-sidebar-navigation-screen-template-part-navigation-menu__title"
+				size="12"
+				upperCase={ true }
+			>
+				{ __( 'Navigation Menus' ) }
+			</Heading>
+			<TemplatePartNavigationMenuList menus={ menus } />
+		</>
+	);
+}

packages/edit-site/src/style.scss

@@ -34,6 +34,7 @@
 @import "./components/sidebar-navigation-screen-page/style.scss";
 @import "./components/sidebar-navigation-screen-template/style.scss";
 @import "./components/sidebar-navigation-screen-templates/style.scss";
+@import "./components/sidebar-navigation-screen-template-part/style.scss";
 @import "./components/sidebar-navigation-subtitle/style.scss";
 @import "./components/site-hub/style.scss";
 @import "./components/sidebar-navigation-screen-navigation-menus/style.scss";