Re: [Qemu-devel] [PATCH V6 08/10] qapi script: do not allow string discriminator

[Markus Armbruster]

Wenchao Xia <address@hidden> writes:

> Signed-off-by: Wenchao Xia <address@hidden>
> ---
>  docs/qapi-code-gen.txt |    8 +++-----
>  scripts/qapi-visit.py  |    6 ++++++
>  2 files changed, 9 insertions(+), 5 deletions(-)
>
> diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
> index a2e7921..c92add9 100644
> --- a/docs/qapi-code-gen.txt
> +++ b/docs/qapi-code-gen.txt
> @@ -123,11 +123,9 @@ And it looks like this on the wire:
>  
>  Flat union types avoid the nesting on the wire. They are used whenever a
>  specific field of the base type is declared as the discriminator ('type' is
> -then no longer generated). The discriminator can be a string field or a
> -predefined enum field. If it is a string field, a hidden enum type will be
> -generated as "[UNION_NAME]Kind". If it is an enum field, a compile time check
> -will be done to verify the correctness. It is recommended to use an enum 
> field.
> -The above example can then be modified as follows:
> +then no longer generated). The discriminator should be a predefined enum 
> field,
> +and a compile time check will be done to verify the correctness. The above
> +example can then be modified as follows:
>  
>   { 'enum': 'BlockdevDriver', 'data': [ 'raw', 'qcow2' ] }
>   { 'type': 'BlockdevCommonOptions',
> diff --git a/scripts/qapi-visit.py b/scripts/qapi-visit.py
> index 3240921..efa7ec3 100644
> --- a/scripts/qapi-visit.py
> +++ b/scripts/qapi-visit.py
> @@ -280,6 +280,12 @@ def generate_visit_union(expr):
>          # Use the predefined enum type as discriminator
>          ret = ""
>          discriminator_type_name = enum_define['enum_name']
> +    elif discriminator:
> +        # Do not allow string discriminator
> +        sys.stderr.write("Discriminator '%s' is not a pre-defined enum "
> +                         "type\n" %
> +                         discriminator)
> +        sys.exit(1)
>      else:
>          # There will always be a discriminator in the C switch code, by 
> default it
>          # is an enum type generated silently as "'%sKind' % (name)"

Why isn't it diagnosed in qapi.py, like all the other semantic errors?

All errors should have a test in tests/qapi-schema/.  I can try to add
tests for you when I rebase your 09/10.