tests: add a qmp success-response test

Verify the usage of this schema feature and the API behaviour.  This
should be the only case where qmp_dispatch() returns NULL.

Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
Signed-off-by: Thomas Huth <thuth@redhat.com>

tests/qapi-schema/qapi-schema-test.json

@@ -137,6 +137,8 @@
   'data': {'ud1a': 'UserDefOne', '*ud1b': 'UserDefOne'},
   'returns': 'UserDefTwo' }
 
+{ 'command': 'cmd-success-response', 'data': {}, 'success-response': false }
+
 # Returning a non-dictionary requires a name from the whitelist
 { 'command': 'guest-get-time', 'data': {'a': 'int', '*b': 'int' },
   'returns': 'int' }

tests/qapi-schema/qapi-schema-test.out

@@ -156,6 +156,8 @@ object q_obj_user_def_cmd2-arg
     member ud1b: UserDefOne optional=True
 command user_def_cmd2 q_obj_user_def_cmd2-arg -> UserDefTwo
    gen=True success_response=True boxed=False oob=False preconfig=False
+command cmd-success-response None -> None
+   gen=True success_response=False boxed=False oob=False preconfig=False
 object q_obj_guest-get-time-arg
     member a: int optional=False
     member b: int optional=True

tests/test-qmp-cmds.c

@@ -32,6 +32,10 @@ void qmp_test_flags_command(Error **errp)
 {
 }
 
+void qmp_cmd_success_response(Error **errp)
+{
+}
+
 Empty2 *qmp_user_def_cmd0(Error **errp)
 {
     return g_new0(Empty2, 1);
@@ -153,6 +157,17 @@ static void test_dispatch_cmd_failure(void)
     qobject_unref(req);
 }
 
+static void test_dispatch_cmd_success_response(void)
+{
+    QDict *req = qdict_new();
+    QDict *resp;
+
+    qdict_put_str(req, "execute", "cmd-success-response");
+    resp = qmp_dispatch(&qmp_commands, QOBJECT(req), false);
+    g_assert_null(resp);
+    qobject_unref(req);
+}
+
 static QObject *test_qmp_dispatch(QDict *req)
 {
     QDict *resp;
@@ -289,6 +304,8 @@ int main(int argc, char **argv)
     g_test_add_func("/qmp/dispatch_cmd", test_dispatch_cmd);
     g_test_add_func("/qmp/dispatch_cmd_failure", test_dispatch_cmd_failure);
     g_test_add_func("/qmp/dispatch_cmd_io", test_dispatch_cmd_io);
+    g_test_add_func("/qmp/dispatch_cmd_success_response",
+                    test_dispatch_cmd_success_response);
     g_test_add_func("/qmp/dealloc_types", test_dealloc_types);
     g_test_add_func("/qmp/dealloc_partial", test_dealloc_partial);