[Freeipa-devel] environment in Param(s)

[Adam Young]

On 08/01/2011 06:34 AM, Alexander Bokovoy wrote:
> Hi,
>
> while investigating #1549 and #1550 I stumbled upon a problem. We create
> Param(s) as read only entities. This means that using standard methods,
> any modifications to Param instances are denied. What happens in #1549
> and #1550 is that the code in Param.validate() relies on availability of
> existing context to determine whether name or cli_name of a param
> instance should be used.
>
> By itself it is fine as context is passed to Param.validate() within
> environment. The decision what to pass is done in Param.__call__():
>
>      def __call__(self, value, **kw):
>          """
>          One stop shopping.
>          """
>          if value in NULLS:
>              value = self.get_default(**kw)
>          else:
>              value = self.convert(self.normalize(value))
>          if hasattr(self, 'env'):
>              self.validate(value, self.env.context)
>          else:
>              self.validate(value)
>          return value
>
> If this Param instance has attribute 'env', we use its context. However,
> the instance in itself is ReadOnly and gets locked at the very end of
> Param.__init__().
>
> So this makes a case when immediately after creating a parameter we
> can't assign it any environment, its environment always stays None and
> the code in __call__() always calls validate() without context.
>
> A fix I found is quite bad as it violates ReadOnly promise:
>
> diff --git a/ipalib/frontend.py b/ipalib/frontend.py
> index 3534310..1c7071a 100644
> --- a/ipalib/frontend.py
> +++ b/ipalib/frontend.py
> @@ -344,6 +344,9 @@ class HasParam(Plugin):
>           for spec in get():
>               param = create_param(spec)
>               if env is None or param.use_in_context(env):
> +                if env is not None and not hasattr(param, 'env'):
> +                    # Force specified environment
> +                    object.__setattr__(param, 'env', env)
>                   yield param
>
>       def _create_param_namespace(self, name, env=None):
>
>
> Does anybody have better suggestion?

What is the env supposed to represent?  Does it pre-exist the Param 
creation?  If so, it should be passed to the Param constructor.

OTOH, if the env is something that can change, then we should not 
require it for the validate call.  Is it possible to validate without an 
env?