Classic Block: Copy/paste broken for empty Classic Block

packages/blocks/src/api/parser/index.ts

@@ -190,10 +190,18 @@ export function parseRawBlock(
 	// It might be a good idea to throw a warning here.
 	// TODO: I'm unsure about the unregisteredFallbackBlock check,
 	// it might ignore some dynamic unregistered third party blocks wrongly.
-	const isFallbackBlock =
-		normalizedBlock.blockName === getFreeformContentHandlerName() ||
+	const isUnregisteredBlock =
 		normalizedBlock.blockName === getUnregisteredTypeHandlerName();
-	if ( ! blockType || ( ! normalizedBlock.innerHTML && isFallbackBlock ) ) {
+
+	const isImplicitFreeformBlock =
+		normalizedBlock.blockName === getFreeformContentHandlerName() &&
+		rawBlock.blockName !== getFreeformContentHandlerName();
+
+	if (
+		! blockType ||
+		( ! normalizedBlock.innerHTML &&
+			( isUnregisteredBlock || isImplicitFreeformBlock ) )
+	) {
 		return;
 	}
 

packages/blocks/src/api/raw-handling/paste-handler.ts

@@ -118,10 +118,11 @@ export function pasteHandler( {
 
 		if ( content.indexOf( '<!-- wp:' ) !== -1 ) {
 			const parseResult = parse( content );
-			const isSingleFreeFormBlock =
+			const isSingleNonEmptyFreeFormBlock =
 				parseResult.length === 1 &&
-				parseResult[ 0 ].name === 'core/freeform';
-			if ( ! isSingleFreeFormBlock ) {
+				parseResult[ 0 ].name === 'core/freeform' &&
+				parseResult[ 0 ].attributes?.content;
+			if ( ! isSingleNonEmptyFreeFormBlock ) {
 				return parseResult;
 			}
 		}

packages/blocks/src/api/serializer.tsx

@@ -415,13 +415,18 @@ export function serializeBlock(
 	const blockName = block.name;
 	const saveContent = getBlockInnerHTML( block );
 
-	if (
-		blockName === getUnregisteredTypeHandlerName() ||
-		( ! isInnerBlocks && blockName === getFreeformContentHandlerName() )
-	) {
+	if ( blockName === getUnregisteredTypeHandlerName() ) {
 		return saveContent;
 	}
 
+	if ( ! isInnerBlocks && blockName === getFreeformContentHandlerName() ) {
+		if ( saveContent ) {
+			return saveContent;
+		}
+
+		return getCommentDelimitedContent( blockName, {}, saveContent );
+	}
+
 	const blockType = getBlockType( blockName );
 	if ( ! blockType ) {
 		return saveContent;