gio/tests: Ensure that a GCancellableSource can be used muliple times

Closes: #774

gio/gcancellable.c

@@ -541,9 +541,11 @@ g_cancellable_cancel (GCancellable *cancellable)
  * signal. Also handles the race condition that may happen
  * if the cancellable is cancelled right before connecting.
  *
- * @callback is called at most once, either directly at the
+ * @callback is called exactly once each time @cancellable is cancelled,
- * time of the connect if @cancellable is already cancelled,
+ * either directly at the time of the connect if @cancellable is already
- * or when @cancellable is cancelled in some thread.
+ * cancelled, or when @cancellable is cancelled in some thread.
+ * In case the cancellable is reset via [method@Gio.Cancellable.reset]
+ * then the callback can be called again if the @cancellable is cancelled.
  *
  * @data_destroy_func will be called when the handler is
  * disconnected, or immediately if the cancellable is already

gio/tests/cancellable.c

@@ -796,6 +796,69 @@ test_cancellable_cancel_reset_connect_races (void)
   g_object_unref (cancellable);
 }
 
+static gboolean
+source_cancelled_counter_cb (GCancellable *cancellable,
+                             gpointer      user_data)
+{
+  guint *n_calls = user_data;
+
+  *n_calls = *n_calls + 1;
+
+  return G_SOURCE_CONTINUE;
+}
+
+static void
+do_nothing (G_GNUC_UNUSED void *user_data)
+{
+  /* An empty timeout/idle once callback function */
+}
+
+static void
+test_cancellable_source_can_be_fired_multiple_times (void)
+{
+  GCancellable *cancellable;
+  GSource *source;
+  guint n_calls = 0;
+
+  g_test_summary ("Test a cancellable source callback can be called multiple times");
+  g_test_bug ("https://gitlab.gnome.org/GNOME/glib/issues/774");
+
+  cancellable = g_cancellable_new ();
+  source = g_cancellable_source_new (cancellable);
+
+  g_source_set_callback (source, G_SOURCE_FUNC (source_cancelled_counter_cb),
+                         &n_calls, NULL);
+  g_source_attach (source, NULL);
+
+  g_cancellable_cancel (cancellable);
+  g_assert_cmpuint (n_calls, ==, 0);
+
+  while (g_main_context_pending (NULL))
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_calls, ==, 1);
+
+  g_cancellable_cancel (cancellable);
+
+  g_timeout_add_once (100, do_nothing, NULL);
+  while (g_main_context_pending (NULL))
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_calls, ==, 1);
+
+  g_cancellable_reset (cancellable);
+  g_cancellable_cancel (cancellable);
+  g_assert_cmpuint (n_calls, ==, 1);
+
+  while (g_main_context_pending (NULL))
+    g_main_context_iteration (NULL, TRUE);
+
+  g_assert_cmpuint (n_calls, ==, 2);
+
+  g_source_unref (source);
+  g_object_unref (cancellable);
+}
+
 int
 main (int argc, char *argv[])
 {
@@ -811,6 +874,7 @@ main (int argc, char *argv[])
   g_test_add_func ("/cancellable/cancel-reset-races", test_cancellable_cancel_reset_races);
   g_test_add_func ("/cancellable/cancel-reset-connect-races", test_cancellable_cancel_reset_connect_races);
   g_test_add_func ("/cancellable-source/threaded-dispose", test_cancellable_source_threaded_dispose);
+  g_test_add_func ("/cancellable-source/can-be-fired-multiple-times", test_cancellable_source_can_be_fired_multiple_times);
 
   return g_test_run ();
 }