Re: [RFC PATCH 1/2] libxl: add Function class to IDL

[Anthony PERARD <anthony.perard@citrix.com>]

On Mon, Jul 27, 2020 at 09:26:32AM -0400, Nick Rosbrook wrote:
> Add a Function and CtxFunction classes to idl.py to allow generator
> scripts to generate wrappers which are repetitive and straight forward
> when doing so by hand. Examples of such functions are the
> device_add/remove functions.
> 
> To start, a Function has attributes for namespace, name, parameters,
> return type, and an indication if the return value should be interpreted as
> a status code. The CtxFunction class extends this by indicating that a
> libxl_ctx is a required parmeter, and can optionally be an async
> function.
> 
> Also, add logic to idl.parse to return the list of functions found in an
> IDL file. For now, have users of idl.py -- i.e. libxl/gentypes.py and
> golang/xenlight/gengotypes.py -- ignore the list of functions returned.
> 
> Signed-off-by: Nick Rosbrook <rosbrookn@ainfosec.com>
> ---
>  
> +class Function(object):
> +    """
> +    A general description of a function signature.
> +
> +    Attributes:
> +      name (str): name of the function, excluding namespace.
> +      params (list of (str,Type)): list of function parameters.
> +      return_type (Type): the Type (if any), returned by the function.
> +      return_is_status (bool): Indicates that the return value should be
> +                               interpreted as an error/status code.

Can we get away without `return_is_status`? Couldn't we try to have
return_type=libxl_error to indicate that return is a kind of status?

> +    """
> +class CtxFunction(Function):
> +    """
> +    A function that requires a libxl_ctx.
> +
> +    Attributes:
> +      is_asyncop (bool): indicates that the function accepts a
> +                         libxl_asyncop_how parameter.

While CtxFunction can be a function that takes `libxl_ctx` as first
parameter, I don't think `is_asyncop` can be used. We can't know if
`ao_how` will be last or not. For some function, `ao_how` is second to
last. So, I guess `ao_how` might need to be listed in `params`

What do you think?

Thanks,

-- 
Anthony PERARD