Matthew Seal

Sorry for the delay in getting to this. So the root problem is that nbconvert never had the ability to parse `application/vnd.jupyter.widget-view+json` message types, which `Output()` use for display purposes....

@jasongrout Can you help confirm expected behavior here? I think I see the pattern being used but I'm not aware if it's documented anywhere and want to make sure I've...

> It is the frontend's responsibility to provide an output widget that knows how to interface with the other parts of the frontend to capture relevant outputs. How does nbconvert...

Ok I'll move this issue to nbclient and see about taking a stab at mimicing the front-end behavior if possible. Thanks for the context.

This is now solved in nbclient, which means nbconvert 6.0 alpha has the fix.

Thanks for reporting and providing a reproducible error. I noticed what's happening is that the child displays are present notebook metadata->widgets namespace, but the `children` subkey has `IPY_MODEL_c72337cc98a94de5adcf9bed7653fb7b` which isn't...

Yes, this issue was resolved in https://github.com/jupyter/nbclient/issues/24 and nbclient >= 0.4.0 has the fix. NBconvert 6.0 (which should be releasing tomorrow) defaults to using nbclient and the issue overall should...

Ok I'll need to dig into why that's happening for altair outputs specifically, might take me a couple days to find time to dig into it though as my free...

As an FYI there are some metadata fields in the schema for hiding input and outputs (`jupyter:source_hidden` and `jupyter:outputs_hidden`) as well as for collapsing outputs (`collapsed`): https://github.com/jupyter/nbformat/blob/master/nbformat/v4/nbformat.v4.schema.json#L195-L239 -- I haven't...

So this is more of an ipython or ipywidgets topic. This has to do with the `notebook` format returning javascript that needs a browser to render correctly. See https://nbconvert.readthedocs.io/en/latest/execute_api.html#widget-state. Normally...