Empty collections handling

[kamilmielnik]

Currently root collections and personal collections are always displayed in the picker, see:

metabase/frontend/src/metabase/common/components/QuestionPicker/utils.ts

Lines 94 to 105 in 1c5e599

	export const isFolder = (
	item: QuestionPickerItem,
	models: CollectionItemModel[],
	) => {
	return (
	item.id === "root" ||
	item.is_personal ||
	(item?.model === "collection" &&
	_.intersection([...(item?.below ?? []), ...(item?.here ?? [])], models)
	.length > 0)
	);
	};

metabase/frontend/src/metabase/common/components/CollectionPicker/components/PersonalCollectionItemList.tsx

Line 51 in 4cbae2e

here: ["collection"], // until this endpoint gives this to us, pretend they all have content

metabase/frontend/src/metabase/common/components/DataPicker/utils.ts

Lines 188 to 190 in 1163109

	if (item.id !== "root" && !item.is_personal && !hasQuestionsOrModels) {
	return false;
	}

This can sometimes lead users to dead ends.

Ideally we'd

update the API to correctly populate personal collections. I think the right way to do this is probably not via search, but should be a special case like collection/personal/items to list all other personal collections with the same shape as collection/:id/items

See Slack thread.

---

This should be covered with tests.

---

We had to remove this assertion in the Data Picker epic because of it:

metabase/e2e/test/scenarios/question/new.cy.spec.js

Lines 198 to 200 in 14e66a0

	cy.findByText(getPersonalCollectionName(USERS.normal)).should(
	"not.exist",
	);

We should bring it back.

[kamilmielnik]

Duplicate of #40924