Fixed error when copying only nested blocks

Author: matthewlipski

packages/core/src/api/serialization/html/sharedHTMLConversion.ts

@@ -35,39 +35,57 @@ export const serializeNodeInner = <BSchema extends BlockSchema>(
 
     // Handles converting `blockContainer` nodes to HTML.
     if (node.type.name === "blockContainer") {
+      const blockContentNode =
+        node.childCount > 0 &&
+        node.firstChild!.type.spec.group === "blockContent"
+          ? node.firstChild!
+          : undefined;
+      const blockGroupNode =
+        node.childCount > 0 && node.lastChild!.type.spec.group === "blockGroup"
+          ? node.lastChild!
+          : undefined;
+
       // Converts `blockContent` node using the custom `blockSpec`'s
       // `toExternalHTML` or `toInternalHTML` function.
-      const blockSpec =
-        editor.schema[node.firstChild!.type.name as keyof BSchema];
-      const toHTML = toExternalHTML
-        ? blockSpec.toExternalHTML
-        : blockSpec.toInternalHTML;
-      const blockContent = toHTML(
-        nodeToBlock(node, editor.schema, editor.blockCache) as SpecificBlock<
-          BlockSchema,
-          keyof BlockSchema
-        >,
-        editor as BlockNoteEditor<BlockSchema>
-      );
+      // Note: While `blockContainer` nodes should always contain a
+      // `blockContent` node according to the schema, PM Fragments don't always
+      // conform to the schema. This is unintuitive but important as it occurs
+      // when copying only nested blocks.
+      if (blockContentNode !== undefined) {
+        const blockSpec =
+          editor.schema[blockContentNode.type.name as keyof BSchema];
+        const toHTML = toExternalHTML
+          ? blockSpec.toExternalHTML
+          : blockSpec.toInternalHTML;
+        const blockContent = toHTML(
+          nodeToBlock(node, editor.schema, editor.blockCache) as SpecificBlock<
+            BlockSchema,
+            keyof BlockSchema
+          >,
+          editor as BlockNoteEditor<BlockSchema>
+        );
+
+        // Converts inline nodes in the `blockContent` node's content to HTML
+        // using their `renderHTML` methods.
+        if (blockContent.contentDOM !== undefined) {
+          if (node.isLeaf) {
+            throw new RangeError(
+              "Content hole not allowed in a leaf node spec"
+            );
+          }
 
-      // Converts inline nodes in the `blockContent` node's content to HTML
-      // using their `renderHTML` methods.
-      if (blockContent.contentDOM) {
-        if (node.isLeaf) {
-          throw new RangeError("Content hole not allowed in a leaf node spec");
+          blockContent.contentDOM.appendChild(
+            serializer.serializeFragment(blockContentNode.content, options)
+          );
         }
 
-        blockContent.contentDOM.appendChild(
-          serializer.serializeFragment(node.firstChild!.content, options)
-        );
+        contentDOM.appendChild(blockContent.dom);
       }
 
-      contentDOM.appendChild(blockContent.dom);
-
       // Converts `blockGroup` node to HTML using its `renderHTML` method.
-      if (node.childCount === 2) {
+      if (blockGroupNode !== undefined) {
         serializer.serializeFragment(
-          Fragment.from(node.content.lastChild),
+          Fragment.from(blockGroupNode),
           options,
           contentDOM
         );