feat(rules): every Maildir folder in the Folder dropdown

The dropdown was built from config, which names one subtree per account
and nothing below it, so it offered five entries and no way to say
Drafts or Sent. A rule wants to target those as often as a whole
account.

NotmuchWorker gains requestFolders/foldersReady, walking the tree from
notmuch_database_get_path() and listing every directory holding cur/.
It belongs there because the database root is notmuch's database.path
and the worker owns the only handle that can answer for it; putting the
root in config would be the second source of truth the design refuses.

From the disk rather than from the index: a folder mbsync created and
nothing has landed in yet is still a folder a rule may target, and a
list derived from indexed message paths would not offer it.

The two tests build their own fixture rather than extending the shared
one, which needs a nested folder and would otherwise move seven count
assertions in unrelated tests. Mutation-checked: flattening the walk to
non-recursive fails the listing test.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

1 files changed, 77 insertions, 0 deletions

diff --git a/tests/test_notmuchworker.cpp b/tests/test_notmuchworker.cpp
index 1db26c7..9068ca3 100644
--- a/tests/test_notmuchworker.cpp
+++ b/tests/test_notmuchworker.cpp
@@ -80,6 +80,9 @@ private slots:
     void messageCountsCountMessagesNotThreads();
     void messageCountsReportAnInvalidQueryAsMinusOne();
 
+    void requestFoldersListsEveryMaildirFolder();
+    void requestFoldersOnUnreadableConfigEmitsError();
+
 private:
     /// Tags of one message, read back through a fresh worker query.
     QStringList tagsOf(const QString &messageId);
@@ -900,5 +903,79 @@ void TestNotmuchWorker::requestDatabaseStatsOnUnreadableConfigEmitsError()
     QVERIFY(ready.isEmpty());
 }
 
+void TestNotmuchWorker::requestFoldersListsEveryMaildirFolder()
+{
+    // Its own fixture rather than the shared one: this needs a NESTED folder,
+    // which is the shape a real account has (<account>/Drafts, not a flat
+    // "drafts"), and adding a message to the shared fixture would move seven
+    // count assertions in other tests for nothing.
+    NotmuchFixture fixture;
+    QVERIFY(fixture.isValid());
+    QVERIFY(fixture.addMessage(QStringLiteral("work/INBOX"),
+                               QStringLiteral("g1@example.org"),
+                               QStringLiteral("Something"),
+                               QStringLiteral("Alice <alice@example.org>"),
+                               QStringLiteral("Mon, 1 Jun 2026 10:00:00 +0000"),
+                               QStringLiteral("body"), false));
+    QVERIFY(fixture.addMessage(QStringLiteral("work/Drafts"),
+                               QStringLiteral("g2@example.org"),
+                               QStringLiteral("Half written"),
+                               QStringLiteral("You <you@example.org>"),
+                               QStringLiteral("Tue, 2 Jun 2026 10:00:00 +0000"),
+                               QStringLiteral("body"), false));
+    QVERIFY2(fixture.index(), qPrintable(fixture.error()));
+
+    // An EMPTY folder, created but never written to. mbsync makes these, and a
+    // list derived from indexed messages would not offer it. A rule may
+    // legitimately target a folder that has nothing in it yet.
+    QDir dir;
+    const QString empty = fixture.maildirPath() + QStringLiteral("/work/Archive");
+    QVERIFY(dir.mkpath(empty + QStringLiteral("/cur")));
+    QVERIFY(dir.mkpath(empty + QStringLiteral("/new")));
+    QVERIFY(dir.mkpath(empty + QStringLiteral("/tmp")));
+
+    NotmuchWorker worker(fixture.configPath());
+    QSignalSpy ready(&worker, &NotmuchWorker::foldersReady);
+
+    worker.requestFolders();
+
+    QCOMPARE(ready.count(), 1);
+    const QStringList folders = ready.first().at(0).toStringList();
+
+    // Paths relative to the database root, which is what a Folder term
+    // compiles a path: against. Drafts is the whole point of the item: the
+    // dialog used to offer one entry per account and nothing below it.
+    QVERIFY(folders.contains(QStringLiteral("work/INBOX")));
+    QVERIFY(folders.contains(QStringLiteral("work/Drafts")));
+    QVERIFY(folders.contains(QStringLiteral("work/Archive")));
+
+    // Not the maildir plumbing, which is not a folder anyone files mail into,
+    // and not the account directory itself, which holds no cur/.
+    QVERIFY(!folders.contains(QStringLiteral("work/INBOX/cur")));
+    QVERIFY(!folders.contains(QStringLiteral("work/INBOX/new")));
+    QVERIFY(!folders.contains(QStringLiteral("work")));
+
+    // Sorted, so the dropdown does not reorder itself between openings with
+    // the same tree on disk. QDir's own order is filesystem order.
+    QStringList sorted = folders;
+    sorted.sort();
+    QCOMPARE(folders, sorted);
+}
+
+void TestNotmuchWorker::requestFoldersOnUnreadableConfigEmitsError()
+{
+    // Fails closed like every other entry point. The dialog then leaves the
+    // dropdown as it was rather than emptying it, since an empty list reads as
+    // "this account has no folders".
+    NotmuchWorker worker(QStringLiteral("/nonexistent/qtmaildir-test/config"));
+    QSignalSpy ready(&worker, &NotmuchWorker::foldersReady);
+    QSignalSpy errors(&worker, &NotmuchWorker::errorOccurred);
+
+    worker.requestFolders();
+
+    QCOMPARE(errors.size(), 1);
+    QVERIFY(ready.isEmpty());
+}
+
 QTEST_MAIN(TestNotmuchWorker)
 #include "test_notmuchworker.moc"