Blocks: Serialize fallback block without comment delimiters

blocks/api/serializer.js

@@ -13,7 +13,7 @@ import { Component, createElement, renderToString, cloneElement, Children } from
 /**
  * Internal dependencies
  */
-import { getBlockType } from './registration';
+import { getBlockType, getUnknownTypeHandlerName } from './registration';
 
 /**
  * Returns the block's default classname from its name
@@ -163,6 +163,13 @@ export function getCommentDelimitedContent( blockName, attributes, content ) {
 	);
 }
 
+/**
+ * Returns the content of a block, including comment delimiters, determining
+ * serialized attributes and content form from the current state of the block.
+ *
+ * @param  {Object} block Block instance
+ * @return {String}       Serialized block
+ */
 export function serializeBlock( block ) {
 	const blockName = block.name;
 	const blockType = getBlockType( blockName );
@@ -178,11 +185,17 @@ export function serializeBlock( block ) {
 
 	const saveAttributes = getCommentAttributes( block.attributes, blockType.attributes );
 
-	if ( 'core/more' === blockName ) {
-		return `<!--more${ saveAttributes.text ? ` ${ saveAttributes.text }` : '' }-->${ saveAttributes.noTeaser ? '\n<!--noteaser-->' : '' }`;
-	}
+	switch ( blockName ) {
+		case 'core/more':
+			const { text, noTeaser } = saveAttributes;
+			return `<!--more${ text ? ` ${ text }` : '' }-->${ noTeaser ? '\n<!--noteaser-->' : '' }`;
+
+		case getUnknownTypeHandlerName():
+			return saveContent;
 
-	return getCommentDelimitedContent( blockName, saveAttributes, saveContent );
+		default:
+			return getCommentDelimitedContent( blockName, saveAttributes, saveContent );
+	}
 }
 
 /**

blocks/api/test/serializer.js

@@ -13,12 +13,19 @@ import serialize, {
 	getSaveContent,
 	serializeAttributes,
 	getCommentDelimitedContent,
+	serializeBlock,
 } from '../serializer';
-import { getBlockTypes, registerBlockType, unregisterBlockType } from '../registration';
+import {
+	getBlockTypes,
+	registerBlockType,
+	unregisterBlockType,
+	setUnknownTypeHandlerName,
+} from '../registration';
 import { createBlock } from '../';
 
 describe( 'block serializer', () => {
 	afterEach( () => {
+		setUnknownTypeHandlerName( undefined );
 		getBlockTypes().forEach( block => {
 			unregisterBlockType( block.name );
 		} );
@@ -257,6 +264,74 @@ describe( 'block serializer', () => {
 		} );
 	} );
 
+	describe( 'serializeBlock()', () => {
+		describe( '"more" block', () => {
+			beforeEach( () => {
+				registerBlockType( 'core/more', {
+					category: 'layout',
+
+					attributes: {
+						text: {
+							type: 'string',
+						},
+						noTeaser: {
+							type: 'boolean',
+							default: false,
+						},
+					},
+
+					save: ( { attributes } ) => attributes.text,
+				} );
+			} );
+
+			it( 'serializes without text', () => {
+				const block = createBlock( 'core/more', {} );
+
+				const content = serializeBlock( block );
+
+				expect( content ).toBe( '<!--more-->' );
+			} );
+
+			it( 'serializes with text', () => {
+				const block = createBlock( 'core/more', {
+					text: 'Read more!',
+				} );
+
+				const content = serializeBlock( block );
+
+				expect( content ).toBe( '<!--more Read more!-->' );
+			} );
+
+			it( 'serializes with no teaser', () => {
+				const block = createBlock( 'core/more', {
+					noTeaser: true,
+				} );
+
+				const content = serializeBlock( block );
+
+				expect( content ).toBe( '<!--more-->\n<!--noteaser-->' );
+			} );
+		} );
+
+		it( 'serializes the fallback block without comment delimiters', () => {
+			registerBlockType( 'core/unknown-block', {
+				category: 'common',
+				attributes: {
+					fruit: {
+						type: 'string',
+					},
+				},
+				save: ( { attributes } ) => attributes.fruit,
+			} );
+			setUnknownTypeHandlerName( 'core/unknown-block' );
+			const block = createBlock( 'core/unknown-block', { fruit: 'Bananas' } );
+
+			const content = serializeBlock( block );
+
+			expect( content ).toBe( 'Bananas' );
+		} );
+	} );
+
 	describe( 'serialize()', () => {
 		it( 'should serialize the post content properly', () => {
 			const blockType = {

blocks/test/fixtures/core__freeform.serialized.html

@@ -1,6 +1,4 @@
-<!-- wp:core/freeform -->
 Testing freeform block with some
 <div class="wp-some-class">
-    HTML <span style="color: red;">content</span>
+	HTML <span style="color: red;">content</span>
 </div>
-<!-- /wp:core/freeform -->