[Discover][Dashboard] Support changing displayed tab on a Dashboard

[kertal]

📓 Summary:

Currently there's no way to edit the displayed Discover session tab on a Dashboard. Users should be able to change which tab is being displayed in a dashboard's Edit Mode, given there are multiple tabs. When a new tab is selected, the Discover embeddable should transition to a loading state and then display the updated data for that specific tab. The change should be saved, when the edited Dashboard is being saved.

UI

✔️Acceptance criteria:

• The currently displayed tab of a Discover session should be edible on a Dashboard in Edit mode
• Discover sessions with multiple tabs should show a dropdown containing all tabs by name
• When the desired tab is selected the UI of the embeddable switches to loading state and the selected tab is being rendered (with updated data)
• This change is saved with the Discover session embeddable state as part of the Dashboard saved object
• There should be no change for Discover sessions by value or Discover sessions by reference with just one tab
• There should be no change in a Dashboards View mode other than the changed tab is being displayed, but not selectable
• There should be functional coverage for this change

[elasticmachine]

Pinging @elastic/kibana-data-discovery (Team:DataDiscovery)

[l-suarez]

I had a chat with @MiloszRadzynski about what happens when a user deletes a tab that was used inside a Discover panel in Dashboards, and I strongly believe we should not fall back to another Discover tab if the author selected tab has been deleted.

The tab is part of the author’s data intent. Substituting it with a different tab (for example, a metrics table instead of a yearly cluster usage view) makes the dashboard incorrect and misleading, even if it technically renders.

Dashboards are expected to be reliable and intentional. Showing the wrong data is worse than showing no data at all.

Proposal:

• If the selected tab no longer exists, the panel should enter an invalid/error state.
• Clear message: “This panel references a Discover tab that no longer exists. "Contact your admin" or "Edit panel" if user has permissions”
• In edit mode, flag the dropdown as invalid and prompt the author to reselect a tab.

Fallbacks make sense to keep things functional and visually acceptable, not for data intent. In this case, a visible error is the correct and more trustworthy UX in my opinion.

cc/ @kertal @ninoslavmiskovic

[ninoslavmiskovic]

Should this happen also if the panel have multiple tabs ? In discover if you have multiple tabs and delete one then we are switched to the last one selected, and do not show an error. Just trying to understand why change this behaviour?

[akowalska622]

I'm also wondering if we should add some warning upon closing a tab, which is used in Dashboards (if technically possible), wdyt?