Legacy Saved Object Import UI - Choices on the index patterns override page are reset

[lucabelluccini]

Kibana version: 7.8.1, 7.9.0

Elasticsearch version: aligned

Browser version: Version 84.0.4147.135 (Official Build) (64-bit)

Browser OS version: MacOS Mojave 10.14.6 (18G4032)

Describe the bug:

Importing several objects in Saved Objects UI and when the imported index patterns do not exist.
If there are multiple index patterns missing, the index patterns override UI is paginated.
If we select an index pattern in any page (except the first one), the UI seems to reset, losing all the selections done on previous pages.

Steps to reproduce:

1. Create 6 visualizations, each one pointing to a different index pattern
2. Export the 6 visualizations
3. Delete the 6 index patterns
4. Import the 6 visualizations, enabling Automatically overwrite all saved objects?
5. Go to the 2nd page, trying to edit the 6th
6. As soon as we choose an index pattern to use, the UI is reset and we go back to the first page
7. Any selection done on the 1st page is lost

Workaround: increase the size of page to 25 rows per page (but only works for less than 25 index patterns).

Expected behavior:

Keep the choices on all the pages and do not reset the UI

Screenshots (if relevant):

Errors in browser console (if relevant):

None in console.

[elasticmachine]

Pinging @elastic/kibana-platform (Team:Platform)

[pgayvallet]

Note that this is only happening when importing in the legacy (json) format. ndjson imports are not using the inline table to choose indexPattern overrides and are not impacted.

That being said, this seems to be the combination of two things:

1. We do no keep the override table state in the Flyout component. For instance, the value property of the select boxes is no set, causing any re-render to redisplay the default

kibana/src/plugins/saved_objects_management/public/management_section/objects_table/components/flyout.tsx

Lines 544 to 550 in 159369b

	return (
	<EuiSelect
	data-test-subj={`managementChangeIndexSelection-${id}`}
	onChange={(e) => this.onIndexChanged(id, e)}
	options={options}
	/>
	);

2. We do not keep the pagination infos (pagination.initialPageIndex + onTableChange), causing any rerender to redisplay the first page due to component re-rendering.

These two things are causing the call to setState in

kibana/src/plugins/saved_objects_management/public/management_section/objects_table/components/flyout.tsx

Lines 446 to 448 in 159369b

	onIndexChanged = (id: string, e: any) => {
	const value = e.target.value;
	this.setState((state) => {

to rerender the flyout content and the underlying EuiInMemoryTable in its initial state when selecting an option in any selectbox.

[pgayvallet]

Blocked by elastic/eui#3982

[pgayvallet]

Removing the regression tag, as it was not introduced by platform migration and was present for as long as we were using EuiInMemoryTable to display the index pattern override table.

[pgayvallet]

elastic/eui#3982 has been addressed. the issue is unblocked.