feat(worker): list every tag in the database

Query bar completion cannot offer tag names without a way to enumerate
them, and libnotmuch had no call wired up for it. Follows the existing
generation-counter pattern; the result crosses the thread boundary as a
QStringList.

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

2 files changed, 27 insertions, 0 deletions

diff --git a/src/notmuchworker.cpp b/src/notmuchworker.cpp
index ed97e39..a5096d2 100644
--- a/src/notmuchworker.cpp
+++ b/src/notmuchworker.cpp
@@ -332,3 +332,24 @@ void NotmuchWorker::applyTags(const TagChange &change)
 
     emit tagsApplied(change);
 }
+
+void NotmuchWorker::requestAllTags(quint64 generation)
+{
+    if (!openReadOnly())
+        return;
+
+    NmTags tags(notmuch_database_get_all_tags(m_db));
+    if (!tags) {
+        emit errorOccurred(QStringLiteral("Cannot list tags"));
+        return;
+    }
+
+    QStringList result;
+    for (; notmuch_tags_valid(tags.get()); notmuch_tags_move_to_next(tags.get()))
+        result.append(QString::fromUtf8(notmuch_tags_get(tags.get())));
+
+    // Sorted once here so no consumer has to sort again. notmuch returns tags
+    // in Xapian term order, which is byte order, not the user's locale order.
+    result.sort();
+    emit allTagsReady(result, generation);
+}
diff --git a/src/notmuchworker.h b/src/notmuchworker.h
index e0c80c6..88187ec 100644
--- a/src/notmuchworker.h
+++ b/src/notmuchworker.h
@@ -69,11 +69,17 @@ public slots:
                             const QStringList &remove,
                             const QString &description);
 
+    /// Every tag in the database, sorted. Feeds query bar completion, which
+    /// cannot offer tag names it has no way to enumerate. Called at startup,
+    /// after a sync, and after a tag mutation introduces an unknown tag.
+    void requestAllTags(quint64 generation);
+
 signals:
     void threadsReady(const QVector<ThreadSummary> &threads, quint64 generation);
     void queryFinished(int totalThreads, quint64 generation);
     void threadLoaded(const QVector<MessageRef> &messages, quint64 generation);
     void tagsApplied(const TagChange &change);
+    void allTagsReady(const QStringList &tags, quint64 generation);
     void errorOccurred(const QString &message);
 
 private: