fix: stop calling a folder empty while a filter chip or category tab hides its mail

components/email/__tests__/email-list-plugin-filters.test.tsx

@@ -71,6 +71,14 @@ describe('plugin list filters in the message list', () => {
     expect(fetchEmails).toHaveBeenCalledTimes(2);
   });
 
+  it('does not call the folder empty while a filter hides its mail', async () => {
+    render(<EmailList emails={[]} />);
+    expect(await screen.findByText('no_emails_description')).toBeInTheDocument();
+    act(() => { fireEvent.click(screen.getByRole('button', { name: 'Open' })); });
+    expect(screen.getByText('no_emails')).toBeInTheDocument();
+    expect(screen.queryByText('no_emails_description')).toBeNull();
+  });
+
   it.each([
     ['a search', { searchQuery: 'invoice' }],
     ['a tag view', { selectedKeyword: 'work' }],

components/email/email-list.tsx

@@ -48,7 +48,7 @@ import { getOwnAddresses } from "@/lib/filters/quick-rule-target";
 import { emitThreadExpand } from "@/lib/plugin-thread-expand";
 import { normalizeAddress } from "@/lib/filters/quick-rules";
 import { PluginSlot } from "@/components/plugins/plugin-slot";
-import { PluginListFilters } from "./plugin-list-filters";
+import { PluginListFilters, useFolderListFiltered } from "./plugin-list-filters";
 import { PluginActions, useFolderAccountKind } from "@/components/plugins/plugin-actions";
 import { useUnreadFirstSection } from "@/hooks/use-unread-first-section";
 import { useTimeoutWhileMounted } from "@/hooks/use-timeout-while-mounted";
@@ -532,6 +532,9 @@ export function EmailList({
   );
   const bulkActionContext = useMemo(() => ({ emailIds: selectedEmailIds }), [selectedEmailIds]);
   const folderAccountKind = useFolderAccountKind();
+  // A filter chip or a category tab on: the folder itself may well have mail.
+  const pluginFilterOn = useFolderListFiltered(effectiveMailboxRole ?? null, folderAccountKind);
+  const listNarrowed = pluginFilterOn || useMessageListTabsStore.getState().getCategoryFilter(effectiveMailboxRole) !== null;
   // "Remove from this folder" (#615): offered for a selection only when every
   // selected message is also in another folder.
   const removeFromFolder = useRemoveFromFolder();
@@ -1222,7 +1225,7 @@ export function EmailList({
             <EmptyState
               icon={isScheduledView ? CalendarClock : isSearching ? SearchX : MailX}
               title={isScheduledView ? t('no_scheduled_emails') : isSearching ? t('no_search_results') : t('no_emails')}
-              description={isScheduledView ? t('no_scheduled_emails_description') : isSearching ? t('no_search_results_description') : t('no_emails_description')}
+              description={isScheduledView ? t('no_scheduled_emails_description') : isSearching ? t('no_search_results_description') : listNarrowed ? undefined : t('no_emails_description')}
               actions={!isScheduledView && isSearching && onClearSearch ? (
                 <Button size="sm" variant="outline" onClick={onClearSearch}>{tSidebar('clear_search')}</Button>
               ) : !isScheduledView && !isSearching && effectiveMailboxRole === 'drafts' && onCompose ? (

components/email/plugin-list-filters.tsx

@@ -5,6 +5,7 @@ import { useTranslations } from "next-intl";
 import { iconForName, X } from "@/components/icons";
 import { cn } from "@/lib/utils";
 import {
+  activeListFilterCondition,
   activeListFilterKeys,
   listFilterApplies,
   listFilterRevision,
@@ -16,6 +17,15 @@ import type { MailAccountKind } from "@/lib/plugin-sandbox/account-kind";
 
 const NONE = new Set<string>();
 
+/** Whether a plugin's filter is narrowing this folder's list right now. */
+export function useFolderListFiltered(mailboxRole: string | null, accountKind: MailAccountKind | null): boolean {
+  return useSyncExternalStore(
+    subscribeListFilters,
+    () => activeListFilterCondition({ role: mailboxRole, accountKind }) !== null,
+    () => false,
+  );
+}
+
 /**
  * The keyword filters plugins offer for this folder (api.ui.setListFilters),
  * as chips in the list header. A chip turns its filter on; an active chip