Re: [Qemu-devel] [PATCH v15 15/23] qmp: Support explicit null during visits

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> Implement the new type_null() callback for the qmp input and
> output visitors. While we don't yet have a use for this in QAPI
> input (the generator will need some tweaks first), some
> potential usages have already been discussed on the list.
> Meanwhile, the output visitor could already output explicit null
> via type_any, but this gives us finer control.
>
> At any rate, it's easy to test that we can round-trip an explicit
> null through manual use of visit_type_null() wrapped by a virtual
> visit_start_struct() walk, even if we can't do the visit in a
> QAPI type.  Repurpose the test_visitor_out_empty test,
> particularly since a future patch will tighten semantics to
> forbid use of qmp_output_get_qobject() without at least one
> intervening visit_type_*.
>
> Signed-off-by: Eric Blake <address@hidden>
[...]
> diff --git a/tests/test-qmp-input-visitor.c b/tests/test-qmp-input-visitor.c
> index c039806..3b6ae92 100644
> --- a/tests/test-qmp-input-visitor.c
> +++ b/tests/test-qmp-input-visitor.c
> @@ -279,6 +279,30 @@ static void test_visitor_in_any(TestInputVisitorData 
> *data,
>      qobject_decref(res);
>  }
>
> +static void test_visitor_in_null(TestInputVisitorData *data,
> +                                 const void *unused)
> +{
> +    Visitor *v;
> +    Error *err = NULL;
> +    char *tmp;
> +
> +    /*
> +     * FIXME: Since QAPI doesn't know the 'null' type yet, we can't
> +     * test visit_type_null() by reading into a QAPI struct then
> +     * checking that it was populated correctly.  The best we can do
> +     * for now is ensure that we consumed null from the input, proven
> +     * by the fact that we can't re-read the key.
> +     */
> +
> +    v = visitor_input_test_init(data, "{ 'a': null }");
> +    visit_start_struct(v, NULL, NULL, 0, &error_abort);
> +    visit_type_null(v, "a", &error_abort);
> +    visit_type_str(v, "a", &tmp, &err);
> +    g_assert(err);

I'd prefer error_free_or_abort().  Can do on commit.

> +    g_assert(!tmp);
> +    visit_end_struct(v, &error_abort);
> +}
> +
>  static void test_visitor_in_union_flat(TestInputVisitorData *data,
>                                         const void *unused)
>  {
[...]