[Discover] Improve display of nested documents when shown as a column with fields API

[wylieconlon]

When using the fields API, nested documents get shown as single-line JSON without formatting. It would be preferable to display each nested JSON object using full formatting if possible.

Requirements to test:

1. Stop fetching data using _source, use the fields API
2. Have a nested mapping in the index containing nested objects
3. Legacy table or data grid are both affected

I will update this issue with an example and mocks.

[elasticmachine]

Pinging @elastic/kibana-app (Team:KibanaApp)

[wylieconlon]

To keep the single-line display, we could use a simple separator like a bullet point:

We could also expand this to a multi-line display if it's helpful by using horizontal separators:

I think the bullet point approach is probably not clear enough, it probably needs to be an icon of some kind.

[kertal]

a multi line approach would not work well in data grid cells due to height limit, but when expanding a cell, this could be helpful
About the separator of array entries, what do you think we could use for a clear separation dear @elastic/kibana-design ? ✂️ ?

[ryankeairns]

a multi line approach would not work well in data grid cells due to height limit, but when expanding a cell, this could be helpful
About the separator of array entries, what do you think we could use for a clear separation dear @elastic/kibana-design ? ✂️ ?

What do you think about using some sort of standard array notation with brackets? ( e.g. [{entry},{entry}] or just [entry],[entry] ). I'm thinking that wrapping each entry would make it immediately clear, even in a short cell, that multiple entries are being displayed as there would be an opening bracket at the front. Conversely, it will be difficult to visually parse a single character between entries, imo.

If the only option is a character between, then a comma or dot may work.

[MJonker]

Is there a way that we ourselves (as customers) determine the UI of a nested field in a column, like field preferred formatting ?

[kertal]

Closing this because it's not planned to be resolved in the foreseeable future. It will be tracked in our Icebox and will be re-opened if our priorities change. Feel free to re-open if you think it should be melted sooner.