[tracker/wip/carlosg/tracker-3.0-api-breaks: 90/95] libtracker-direct: Ensure queries get cancelled after close()

[Carlos Garnacho <carlosg src gnome org>]

commit 08272f65b6eb76d6ac59df0a8b2a65f8ad2add11
Author: Carlos Garnacho <carlosg gnome org>
Date:   Tue Feb 4 23:59:44 2020 +0100

    libtracker-direct: Ensure queries get cancelled after close()
    
    The query thread pool does not get awaited for completion, which
    means later operations should error out orderly. Ensure this
    actually happens, as documented in tracker_sparql_connection_close().

 src/libtracker-direct/tracker-direct.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)
---
diff --git a/src/libtracker-direct/tracker-direct.c b/src/libtracker-direct/tracker-direct.c
index 0155a1fcc..8527f9672 100644
--- a/src/libtracker-direct/tracker-direct.c
+++ b/src/libtracker-direct/tracker-direct.c
@@ -45,6 +45,7 @@ struct _TrackerDirectConnectionPrivate
        GList *notifiers;
 
        guint initialized : 1;
+       guint closing     : 1;
 };
 
 enum {
@@ -148,12 +149,26 @@ static void
 query_thread_pool_func (gpointer data,
                         gpointer user_data)
 {
+       TrackerDirectConnection *conn = user_data;
+       TrackerDirectConnectionPrivate *priv;
        TrackerSparqlCursor *cursor;
        GTask *task = data;
        TaskData *task_data = g_task_get_task_data (task);
        GError *error = NULL;
 
        g_assert (task_data->type == TASK_TYPE_QUERY);
+
+       priv = tracker_direct_connection_get_instance_private (conn);
+
+       if (priv->closing) {
+               g_task_return_new_error (task,
+                                        G_IO_ERROR,
+                                        G_IO_ERROR_CONNECTION_CLOSED,
+                                        "Connection is closed");
+               g_object_unref (task);
+               return;
+       }
+
        cursor = tracker_sparql_connection_query (TRACKER_SPARQL_CONNECTION (g_task_get_source_object (task)),
                                                  task_data->query,
                                                  g_task_get_cancellable (task),
@@ -898,6 +913,7 @@ tracker_direct_connection_close (TrackerSparqlConnection *self)
 
        conn = TRACKER_DIRECT_CONNECTION (self);
        priv = tracker_direct_connection_get_instance_private (conn);
+       priv->closing = TRUE;
 
        if (priv->update_thread) {
                g_thread_pool_free (priv->update_thread, TRUE, TRUE);