Re: [Qemu-devel] [PATCH v11 03/15] qapi: Forbid 'any' inside an alternate

[Markus Armbruster]

Eric Blake <address@hidden> writes:

> The whole point of an alternate is to allow some type-safety while
> still accepting more than one JSON type.  Meanwhile, the 'any'
> type exists to bypass type-safety altogether.  The two are
> incompatible: you can't accept every type, and still tell which
> branch of the alternate to use for the parse; fix this to give a
> sane error instead of a Python stack trace.
>
> Signed-off-by: Eric Blake <address@hidden>
>
> ---
> v11: new patch
> ---
>  scripts/qapi.py                      | 5 ++++-
>  tests/Makefile                       | 1 +
>  tests/qapi-schema/alternate-any.err  | 1 +
>  tests/qapi-schema/alternate-any.exit | 1 +
>  tests/qapi-schema/alternate-any.json | 4 ++++
>  tests/qapi-schema/alternate-any.out  | 0
>  6 files changed, 11 insertions(+), 1 deletion(-)
>  create mode 100644 tests/qapi-schema/alternate-any.err
>  create mode 100644 tests/qapi-schema/alternate-any.exit
>  create mode 100644 tests/qapi-schema/alternate-any.json
>  create mode 100644 tests/qapi-schema/alternate-any.out
>
> diff --git a/scripts/qapi.py b/scripts/qapi.py
> index f97236f..17bf633 100644
> --- a/scripts/qapi.py
> +++ b/scripts/qapi.py
> @@ -629,7 +629,10 @@ def check_alternate(expr, expr_info):
>                     value,
>                     allow_metas=['built-in', 'union', 'struct', 'enum'])
>          qtype = find_alternate_member_qtype(value)
> -        assert qtype
> +        if not qtype:
> +            raise QAPIExprError(expr_info,
> +                                "Alternate '%s' member '%s' cannot use "
> +                                "type '%s'" % (name, key, value))
>          if qtype in types_seen:
>              raise QAPIExprError(expr_info,
>                                  "Alternate '%s' member '%s' can't "

Interestingly, find_alternate_member_qtype(T) can return None in two
ways: when builtin_types[T] is None (only for T == 'any'), and when T is
neither built-in, struct, enum or union (it must be alternate then).

This leads to the question whether this patch catches exactly 'any', as
the commit message claims, or alternate as well.

> diff --git a/tests/Makefile b/tests/Makefile
> index c1c605f..7c66d16 100644
> --- a/tests/Makefile
> +++ b/tests/Makefile
> @@ -241,6 +241,7 @@ check-qtest-xtensaeb-y = $(check-qtest-xtensa-y)
>
>  check-qtest-generic-y += tests/qom-test$(EXESUF)
>
> +qapi-schema += alternate-any.json
>  qapi-schema += alternate-array.json
>  qapi-schema += alternate-base.json
>  qapi-schema += alternate-clash.json
> diff --git a/tests/qapi-schema/alternate-any.err 
> b/tests/qapi-schema/alternate-any.err
> new file mode 100644
> index 0000000..aaa0154
> --- /dev/null
> +++ b/tests/qapi-schema/alternate-any.err
> @@ -0,0 +1 @@
> +tests/qapi-schema/alternate-any.json:2: Alternate 'Alt' member 'one' cannot 
> use type 'any'
> diff --git a/tests/qapi-schema/alternate-any.exit 
> b/tests/qapi-schema/alternate-any.exit
> new file mode 100644
> index 0000000..d00491f
> --- /dev/null
> +++ b/tests/qapi-schema/alternate-any.exit
> @@ -0,0 +1 @@
> +1
> diff --git a/tests/qapi-schema/alternate-any.json 
> b/tests/qapi-schema/alternate-any.json
> new file mode 100644
> index 0000000..e47a73a
> --- /dev/null
> +++ b/tests/qapi-schema/alternate-any.json
> @@ -0,0 +1,4 @@
> +# we do not allow the 'any' type as an alternate branch
> +{ 'alternate': 'Alt',
> +  'data': { 'one': 'any',
> +            'two': 'int' } }
> diff --git a/tests/qapi-schema/alternate-any.out 
> b/tests/qapi-schema/alternate-any.out
> new file mode 100644
> index 0000000..e69de29

Could use a test for alternate member of alternate type.