onLoad content is added to undo stack

[mirka]

Despite the intent of this code to prevent initial onLoad content from being added to the undo stack, it does get added and is undoable:

isolated-block-editor/src/components/block-editor-contents/index.js

Lines 75 to 86 in 82b69ed

	// Set initial content, if we have any, but only if there is no existing data in the editor (from elsewhere)
	useEffect( () => {
	const loadData = async () => {
	const initialContent = await getInitialContent( settings, onLoad );
	if ( initialContent.length > 0 && ( ! blocks || blocks.length === 0 ) ) {
	updateBlocksWithoutUndo( initialContent );
	}
	};
	loadData();
	}, [] );

(This behavior was fixed for undo in collab mode #68, but is not yet fixed for the non-collab case.)

Steps to reproduce

For convenience, here's a branch with a Storybook story for onLoad and a failing UI integration test: https://github.com/Automattic/isolated-block-editor/tree/test/onload-undo

1. Load an iso-editor with some onLoad content.
2. Once the initial content loads, the Undo button is active.
3. When you trigger an undo, you can wipe out the initial content.

Expected behavior

The initial onLoad content is not undoable.

[johngodley]

Ah, I've been meaning to look into this - thanks for debugging it!