Inherit post type from template slug

packages/editor/src/components/provider/index.js

@@ -4,7 +4,11 @@
 import { useEffect, useLayoutEffect, useMemo } from '@wordpress/element';
 import { useDispatch, useSelect } from '@wordpress/data';
 import { __ } from '@wordpress/i18n';
-import { EntityProvider, useEntityBlockEditor } from '@wordpress/core-data';
+import {
+	EntityProvider,
+	useEntityBlockEditor,
+	store as coreStore,
+} from '@wordpress/core-data';
 import {
 	BlockEditorProvider,
 	BlockContextProvider,
@@ -48,7 +52,6 @@ const noop = () => {};
  */
 const NON_CONTEXTUAL_POST_TYPES = [
 	'wp_block',
-	'wp_template',
 	'wp_navigation',
 	'wp_template_part',
 ];
@@ -161,31 +164,57 @@ export const ExperimentalEditorProvider = withRegistryProvider(
 		BlockEditorProviderComponent = ExperimentalBlockEditorProvider,
 		__unstableTemplate: template,
 	} ) => {
-		const { editorSettings, selection, isReady, mode } = useSelect(
-			( select ) => {
+		const { editorSettings, selection, isReady, mode, postTypes } =
+			useSelect( ( select ) => {
 				const {
 					getEditorSettings,
 					getEditorSelection,
 					getRenderingMode,
 					__unstableIsEditorReady,
 				} = select( editorStore );
+				const { getPostTypes } = select( coreStore );
+
 				return {
 					editorSettings: getEditorSettings(),
 					isReady: __unstableIsEditorReady(),
 					mode: getRenderingMode(),
 					selection: getEditorSelection(),
+					postTypes:
+						getPostTypes( { per_page: -1 } )?.map(
+							( entity ) => entity.slug
+						) || [],
 				};
-			},
-			[]
-		);
+			}, [] );
 		const shouldRenderTemplate = !! template && mode !== 'post-only';
 		const rootLevelPost = shouldRenderTemplate ? template : post;
 		const defaultBlockContext = useMemo( () => {
-			const postContext =
+			const postContext = {};
+			// If it is a template, try to inherit the post type from the slug.
+			if ( post.type === 'wp_template' ) {
+				if ( ! post.is_custom ) {
+					const [ kind ] = post.slug.split( '-' );
+					switch ( kind ) {
+						case 'page':
+							postContext.postType = 'page';
+							break;
+						case 'single':
+							// Infer the post type from the slug.
+							const match = post.slug.match(
+								`^single-(${ postTypes.join( '|' ) })(?:-.+)?$`
+							);
+							if ( match ) {
+								postContext.postType = match[ 1 ];
+							}
+							break;
+					}
+				}
+			} else if (
 				! NON_CONTEXTUAL_POST_TYPES.includes( rootLevelPost.type ) ||
 				shouldRenderTemplate
-					? { postId: post.id, postType: post.type }
-					: {};
+			) {
+				postContext.postId = post.id;
+				postContext.postType = post.type;
+			}
 
 			return {
 				...postContext,
@@ -200,6 +229,7 @@ export const ExperimentalEditorProvider = withRegistryProvider(
 			post.type,
 			rootLevelPost.type,
 			rootLevelPost.slug,
+			postTypes,
 		] );
 		const { id, type } = rootLevelPost;
 		const blockEditorSettings = useBlockEditorSettings(