fix: show localized system folder names in the filter rule folder picker

src/components/__tests__/filter-folder-labels.test.ts

@@ -0,0 +1,55 @@
+// The filter rule's "Move to folder" picker listed the server's folder names
+// ("Sent Items", "Junk Mail", "Deleted Items") where the rest of the app
+// shows the localized role names (localizeMailboxName).
+import { describe, expect, it, vi } from 'vitest';
+import fs from 'node:fs';
+import path from 'node:path';
+
+vi.mock('expo-localization', () => ({ getLocales: () => [] }));
+
+import { translate } from '../../i18n';
+import { buildMailboxTargets } from '../../lib/sieve/rule-actions';
+import { folderOptionLabel, mailboxesByTargetId } from '../filters/folder-option-label';
+import type { Mailbox } from '../../api/types';
+
+const mb = (id: string, name: string, role: string | null, parentId: string | null = null): Mailbox => ({
+  id, name, role, parentId, sortOrder: 0, totalEmails: 0, unreadEmails: 0, totalThreads: 0, unreadThreads: 0,
+  myRights: {} as Mailbox['myRights'], isSubscribed: true,
+} as unknown as Mailbox);
+
+const mailboxes = [
+  mb('i', 'Inbox', 'inbox'),
+  mb('s', 'Sent Items', 'sent'),
+  mb('j', 'Junk Mail', 'junk'),
+  mb('d', 'Deleted Items', 'trash'),
+  mb('p', 'Projects', null),
+  mb('a', 'Alpha', null, 'p'),
+];
+
+function labels(locale: 'en' | 'de') {
+  const t = (key: string, fallback?: string) => translate(locale, key, fallback);
+  const byId = mailboxesByTargetId(mailboxes);
+  return Object.fromEntries(buildMailboxTargets(mailboxes).map((target) => [target.id, folderOptionLabel(target, byId.get(target.id), t)]));
+}
+
+describe('filter rule folder picker labels', () => {
+  it('names system folders by role, like the sidebar', () => {
+    const en = labels('en');
+    expect(en.s).toBe(translate('en', 'sidebar.mailboxes.sent'));
+    expect(en.j).toBe(translate('en', 'sidebar.mailboxes.spam'));
+    expect(en.d).toBe(translate('en', 'sidebar.mailboxes.trash'));
+    expect(en.s).not.toBe('Sent Items');
+    expect(labels('de').d).toBe(translate('de', 'sidebar.mailboxes.trash'));
+  });
+
+  it('keeps user folders and their indent', () => {
+    const en = labels('en');
+    expect(en.p).toBe('Projects');
+    expect(en.a).toBe('   Alpha');
+  });
+
+  it('is what the rule editor lists', () => {
+    const source = fs.readFileSync(path.resolve(__dirname, '../filters/FilterRuleModal.tsx'), 'utf8');
+    expect(source).toContain('label: folderOptionLabel(target, mailboxById.get(target.id), t)');
+  });
+});

src/components/filters/FilterRuleModal.tsx

@@ -45,6 +45,7 @@ import { SafeAreaModal } from '../SafeAreaModal';
 import { useFilterStore } from '../../stores/filter-store';
 import { forwardsOfEditedRule, ruleForwardLimit } from '../../lib/sieve/forward-limit';
 import { MODAL_ORIENTATIONS } from '../../lib/modal-orientations';
+import { folderOptionLabel, mailboxesByTargetId } from './folder-option-label';
 import { useModalKeyboardPadding } from '../../lib/sheet-bottom-inset';
 
 const ALL_FIELDS: FilterConditionField[] = ['from', 'to', 'cc', 'subject', 'header', 'size', 'body', 'attachment', 'all'];
@@ -131,6 +132,7 @@ export function FilterRuleModal({
   const periodProblem = periodOn ? periodError(activeFrom, activeUntil) : null;
 
   const mailboxTargets = useMemo(() => buildMailboxTargets(mailboxes), [mailboxes]);
+  const mailboxById = useMemo(() => mailboxesByTargetId(mailboxes), [mailboxes]);
 
   // A message can collect only so many forwards on the server (#1155, #1208).
   const listedRules = useFilterStore((s) => s.rules);
@@ -216,7 +218,10 @@ export function FilterRuleModal({
   // listed (deleted, or its account's folders not loaded) stays selectable
   // under its path, so saving doesn't silently retarget the rule.
   const folderOptions = (action: FilterAction) => {
-    const options = mailboxTargets.map((target) => ({ value: target.id, label: target.label }));
+    const options = mailboxTargets.map((target) => ({
+      value: target.id,
+      label: folderOptionLabel(target, mailboxById.get(target.id), t),
+    }));
     const selected = mailboxIdFor(action, mailboxTargets);
     if (!options.some((o) => o.value === selected) && (selected || action.value)) {
       options.unshift({ value: selected, label: action.value || selected });

src/components/filters/folder-option-label.ts

@@ -0,0 +1,27 @@
+import { localizeMailboxName } from '../../lib/mailbox-label';
+import type { MailboxTarget } from '../../lib/sieve/rule-actions';
+import type { Mailbox } from '../../api/types';
+
+type Translate = (key: string, fallback?: string) => string;
+
+/**
+ * A filter rule's folder picker row: the folder's indent and its name as the
+ * rest of the app shows it. The targets carry the server name, so system
+ * folders read "Sent Items", "Junk Mail" or "Deleted Items" here and
+ * "Sent", "Spam" or "Trash" everywhere else. The rule itself keeps the
+ * server path (fileinto needs it); only the label changes.
+ */
+export function folderOptionLabel(
+  target: MailboxTarget,
+  mailbox: Pick<Mailbox, 'role' | 'name'> | undefined,
+  t: Translate,
+): string {
+  if (!mailbox?.role) return target.label;
+  const indent = /^ */.exec(target.label)?.[0] ?? '';
+  return indent + localizeMailboxName(mailbox.role, mailbox.name, t);
+}
+
+/** Mailboxes by the id the targets use (the server id of a shared folder). */
+export function mailboxesByTargetId(mailboxes: Mailbox[]): Map<string, Mailbox> {
+  return new Map(mailboxes.map((m) => [m.originalId ?? m.id, m]));
+}