changeAttribute converter consumes even if element creators returns null

[scofalik]

As in title, changeAttribute converter first consumes consumables even if it is not going to do anything because elementCreators returned null. This means that changeAttribute cannot be "aborted" using a proper (if statement) in a callback.

In contrary, wrap does it correctly:

return ( evt, data, conversionApi ) => {
	const oldViewElement = elementCreator( data.attributeOldValue, conversionApi.writer );
	const newViewElement = elementCreator( data.attributeNewValue, conversionApi.writer );

	if ( !oldViewElement && !newViewElement ) {
		return;
	}

	if ( !conversionApi.consumable.consume( data.item, evt.name ) ) {
		return;
	}
	
	// ... convert ...
};

[Reinmar]

Any chance it's related to https://github.com/ckeditor/ckeditor5-font/issues/12?

[scofalik]

I don't think so. 😢

[Reinmar]

@jodator clarified that the issue with font is caused by https://github.com/ckeditor/ckeditor5-engine/issues/1348, so I'm fine with that :D