Returning from the reader/message screen to the inbox briefly showed the
"No messages" empty state and reloaded: the inbox's only Paging presenter
(collectAsLazyPagingItems) is torn down while a message is open, so the
cachedIn pager loses its downstream collector. Opening an unread message
writes setRead, invalidating the Room PagingSource; with nothing collecting,
the fresh generation only cold-loaded once the inbox re-entered composition —
a multi-second stall plus a one-frame empty-state flash. (The empty-state
gate itself already landed with #214/#223.)
Add an always-on, invisible PagingDataPresenter in MailboxViewModel that stays
subscribed to the cached paged flow across the reader visit (collectLatest
hands each new generation to collectFrom), so the post-setRead generation
loads in the background and the return replays a full window with no empty
frame.
Tests:
- MailboxViewModelTest: a real, invalidatable Pager proves the pager loads its
initial window and reloads after invalidation with no UI collector attached.
- MailboxScreenTest: the empty state is held back while refresh is Loading and
shown only once the pager settles genuinely empty, driven via PagingData.from
with explicit LoadStates through a new FakeMailRepository paged override.
Closes#219
Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>
JMR-devandClaude Opus 4.8
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