make finding inserter blocks for template locked independent of block…

… name

packages/block-editor/src/components/inserter/hooks/use-block-types-state.js

@@ -24,24 +24,23 @@ import { store as blockEditorStore } from '../../../store';
  */
 const useBlockTypesState = ( rootClientId, onInsert ) => {
 	const [ allItems ] = useSelect( ( select ) => {
-		const { getBlocksByName, getInserterItems } =
-			select( blockEditorStore );
+		let availableItems = select( blockEditorStore ).getInserterItems( '' );
 
-		// Try the empty root first.
-		const rootInserterItems = getInserterItems( '' );
-		if ( rootInserterItems.length ) {
-			return [ rootInserterItems ];
+		// use current selection as root for situations like
+		// template locked mode
+		const rootBlocks = select( blockEditorStore ).getBlocks();
+		while ( availableItems.length === 0 ) {
+			for ( const block of rootBlocks ) {
+				availableItems = select( blockEditorStore ).getInserterItems(
+					block.clientId
+				);
+				if ( availableItems.length ) {
+					break;
+				}
+			}
 		}
-
-		const postContentBlock = getBlocksByName( 'core/post-content' );
-
-		if ( postContentBlock.length ) {
-			return [ getInserterItems( postContentBlock[ 0 ] ) ];
-		}
-
-		// Failsafe
-		return [ [] ];
-	}, [] );
+		return [ availableItems ];
+	} );
 
 	const [ items ] = useSelect(
 		( select ) => [

packages/block-editor/src/components/inserter/hooks/use-insertion-point.js

@@ -135,6 +135,35 @@ function useInsertionPoint( {
 							_destinationRootClientId
 						)
 					);
+				if ( ! canInsertBlocks && normalizedBlocks.length === 1 ) {
+					// If it's not possible to insert the block in the current location, try to find a new location up the tree
+					while (
+						! canInsertBlockType(
+							normalizedBlocks[ 0 ].name,
+							_destinationRootClientId
+						)
+					) {
+						// save the index of the previous destination root client ID
+						const _previousDestinationRootClientId =
+							_destinationRootClientId;
+						_destinationIndex =
+							getBlockIndex( _previousDestinationRootClientId ) +
+							1;
+
+						// get the parent of the current destination root client ID
+						_destinationRootClientId = getBlockRootClientId(
+							_destinationRootClientId
+						);
+
+						// Break the loop if we searched the whole tree
+						if (
+							_previousDestinationRootClientId ===
+							_destinationRootClientId
+						) {
+							break;
+						}
+					}
+				}
 
 				while ( ! canInsertBlocks() ) {
 					_destinationIndex =