Can't call `blocksToHTMLLossy` on document with React custom blocks without instantiating a BlockNoteView

[blx]

Describe the bug <what's going wrong!?>

I want to render a document of blocks to HTML, "headlessly" ie. without showing the editor. But when some of my custom blocks are React-rendered (defined via createReactBlockSpec), an error is thrown when exporting to HTML without having instantiated a BlockNoteView.

blocksToHTMLLossy(), somewhere down the stack, depends on contentComponent being set on the inner editor._tiptapEditor (here), which is done by a useEffect in EditorContent that mutates the editor passed in , and EditorContent doesn't come into play without having a BlockNoteView.

I think this specific state of affairs was introduced in https://github.com/TypeCellOS/BlockNote/pull/641, but I haven't checked whether this would have worked before that.

For now, I'm just rendering a BlockNoteView on a throwaway React root, in order to get the mutation from EditorContent applied, which is fine, but a bit clunky.

I appreciate this is probably not a common use case 🙃

To Reproduce

const toHTML = async (blocks, schema=null) => BlockNoteEditor.create({
  initialContent: blocks,
  ...(schema ? { schema } : {})
}).blocksToHTMLLossy();

// Default schema block works fine:
console.log(await toHTML([{ type: 'paragraph', content: 'heya' }]));

// React-based custom element doesn't work...
const somethingBlock = createReactBlockSpec(
  { type: 'something', content: 'none', propSchema: {} },
  { render() { return <i>A constant something</i> } }
)
const customSchema = BlockNoteSchema.create({ blockSpecs: { something: somethingBlock } })

// ...Throws error:
console.log(await toHTML([{type: 'something'}], customSchema))

// But this works:
const editor = BlockNoteEditor.create({ initialContent: [{type: 'something'}], schema: customSchema });
await new Promise((resolve, reject) => {
  const tmpRoot = ReactDOMClient.createRoot(document.createElement('div'));
  tmpRoot.render(React.createElement(() => {
    useEffect(() => { resolve(); }, []);
    return React.createElement(BlockNoteView, { editor });
  }));
});
console.log(await editor.blocksToHTMLLossy());

The error thrown is:

Uncaught (in promise) TypeError: t._tiptapEditor.contentComponent is undefined
    Ce ReactRenderUtil.ts:13
    toExternalHTML ReactBlockSpec.tsx:213
    Kt sharedHTMLConversion.ts:70
    serializeNodeInner externalHTMLExporter.ts:66
    serializeFragment index.js:3273
    forEach index.js:250
    serializeFragment index.js:3247
    Kt sharedHTMLConversion.ts:109
    serializeNodeInner externalHTMLExporter.ts:66
    serializeFragment index.js:3273
    forEach index.js:250
    serializeFragment index.js:3247
    Jt sharedHTMLConversion.ts:124
    exportProseMirrorFragment externalHTMLExporter.ts:79
    exportBlocks externalHTMLExporter.ts:90
    blocksToHTMLLossy BlockNoteEditor.ts:907

<clear steps to reproduce are super helpful! Best is to provide an online sandbox, click to create one>

Misc

• Node version:
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• Browser:
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