Re: [Qemu-devel] [PATCH RFC 07/10] qapi script: support direct inheritance for struct

[Eric Blake <eblake@redhat.com>]

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On 11/04/2013 05:37 PM, Wenchao Xia wrote:
> Now it is possible to inherit another struct inside data directly,
> which saves trouble to define trivial structure.
> 
> Signed-off-by: Wenchao Xia <xiawenc@linux.vnet.ibm.com>
> ---
>  docs/qapi-code-gen.txt |   21 +++++++++++++++++++++
>  scripts/qapi-visit.py  |   14 ++++++++++----
>  2 files changed, 31 insertions(+), 4 deletions(-)
> 
> diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
> index 0728f36..3e42ff4 100644
> --- a/docs/qapi-code-gen.txt
> +++ b/docs/qapi-code-gen.txt
> @@ -70,6 +70,27 @@ both fields like this:
>   { "file": "/some/place/my-image",
>     "backing": "/some/place/my-backing-file" }
>  
> +It is possible to directly inherit other struct by keyword '_base':
> +
> + { 'type': 'NetworkConnectionInfo', 'data': { 'host': 'str', 'service': 'str' } }
> + { 'type': 'VncConnectionInfo',
> +   'data': {
> +      'server': {
> +          '_base': 'NetworkConnectionInfo',

Interesting idea for shorthand.  However, I would suggest that you pick
a different character than '_', since '_' is valid in names.  That is,
we already have special handling of leading '*' to mark a field as
optional, so I suggest something like '^' to mark a base class.  By
using a non-name character, it becomes more obvious that the leading
character has a special meaning to the qapi generator.

I'm also not convinced yet that we want this shorthand; in particular,
I'm worried whether it will make the introspection patches harder to write.

-- 
Eric Blake   eblake redhat com    +1-919-301-3266
Libvirt virtualization library http://libvirt.org


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