Fail gracefully when block in createBlock function is not registered

packages/blocks/src/api/factory.js

@@ -17,6 +17,7 @@ import {
 	getGroupingBlockName,
 } from './registration';
 import {
+	isBlockRegistered,
 	normalizeBlockType,
 	__experimentalSanitizeBlockAttributes,
 } from './utils';
@@ -31,6 +32,14 @@ import {
  * @return {Object} Block object.
  */
 export function createBlock( name, attributes = {}, innerBlocks = [] ) {
+	if ( ! isBlockRegistered( name ) ) {
+		return createBlock( 'core/missing', {
+			originalName: name,
+			originalContent: '',
+			originalUndelimitedContent: '',
+		} );
+	}
+
 	const sanitizedAttributes = __experimentalSanitizeBlockAttributes(
 		name,
 		attributes
@@ -94,15 +103,22 @@ export function __experimentalCloneSanitizedBlock(
 	mergeAttributes = {},
 	newInnerBlocks
 ) {
+	const { name } = block;
+
+	if ( ! isBlockRegistered( name ) ) {
+		return createBlock( 'core/missing', {
+			originalName: name,
+			originalContent: '',
+			originalUndelimitedContent: '',
+		} );
+	}
+
 	const clientId = uuid();
 
-	const sanitizedAttributes = __experimentalSanitizeBlockAttributes(
-		block.name,
-		{
-			...block.attributes,
-			...mergeAttributes,
-		}
-	);
+	const sanitizedAttributes = __experimentalSanitizeBlockAttributes( name, {
+		...block.attributes,
+		...mergeAttributes,
+	} );
 
 	return {
 		...block,
@@ -583,20 +599,11 @@ export function switchToBlockType( blocks, name ) {
  *
  * @return {Object} block.
  */
-export const getBlockFromExample = ( name, example ) => {
-	try {
-		return createBlock(
-			name,
-			example.attributes,
-			( example.innerBlocks ?? [] ).map( ( innerBlock ) =>
-				getBlockFromExample( innerBlock.name, innerBlock )
-			)
-		);
-	} catch {
-		return createBlock( 'core/missing', {
-			originalName: name,
-			originalContent: '',
-			originalUndelimitedContent: '',
-		} );
-	}
-};
+export const getBlockFromExample = ( name, example ) =>
+	createBlock(
+		name,
+		example.attributes,
+		( example.innerBlocks ?? [] ).map( ( innerBlock ) =>
+			getBlockFromExample( innerBlock.name, innerBlock )
+		)
+	);

packages/blocks/src/api/templates.js

@@ -109,23 +109,12 @@ export function synchronizeBlocksWithTemplate( blocks = [], template ) {
 				attributes
 			);
 
-			let [ blockName, blockAttributes ] =
+			const [ blockName, blockAttributes ] =
 				convertLegacyBlockNameAndAttributes(
 					name,
 					normalizedAttributes
 				);
 
-			// If a Block is undefined at this point, use the core/missing block as
-			// a placeholder for a better user experience.
-			if ( undefined === getBlockType( blockName ) ) {
-				blockAttributes = {
-					originalName: name,
-					originalContent: '',
-					originalUndelimitedContent: '',
-				};
-				blockName = 'core/missing';
-			}
-
 			return createBlock(
 				blockName,
 				blockAttributes,

packages/blocks/src/api/test/utils.js

@@ -12,6 +12,7 @@ import {
 	isUnmodifiedDefaultBlock,
 	getAccessibleBlockLabel,
 	getBlockLabel,
+	isBlockRegistered,
 	__experimentalSanitizeBlockAttributes,
 	getBlockAttributesNamesByRole,
 	isContentBlock,
@@ -213,6 +214,20 @@ describe( 'getAccessibleBlockLabel', () => {
 	} );
 } );
 
+describe( 'isBlockRegistered', () => {
+	it( 'returns true if the block is registered', () => {
+		registerBlockType( 'core/test-block', { title: 'Test block' } );
+		expect( isBlockRegistered( 'core/test-block' ) ).toBe( true );
+		unregisterBlockType( 'core/test-block' );
+	} );
+
+	it( 'returns false if the block is not registered', () => {
+		expect( isBlockRegistered( 'core/not-registered-test-block' ) ).toBe(
+			false
+		);
+	} );
+} );
+
 describe( 'sanitizeBlockAttributes', () => {
 	afterEach( () => {
 		getBlockTypes().forEach( ( block ) => {

packages/blocks/src/api/utils.js

@@ -266,6 +266,17 @@ export function getDefault( attributeSchema ) {
 	}
 }
 
+/**
+ * Check if a block is registered.
+ *
+ * @param {string} name The block's name.
+ *
+ * @return {boolean} Whether the block is registered.
+ */
+export function isBlockRegistered( name ) {
+	return getBlockType( name ) !== undefined;
+}
+
 /**
  * Ensure attributes contains only values defined by block type, and merge
  * default values for missing attributes.