[py-dev] Resource providers

[holger krekel]

On Tue, Jun 26, 2012 at 15:13 +0100, Floris Bruynooghe wrote:
> Another remark about this.  If my use-case of dynamically creating
> funcargs/resources is making this too complicated then feel free to
> ignore it for now.  As you rightly point out it is not that cumbersome
> to achieve the same with the existing funcargs.  See it more as a
> nice-to-have but I don't want it to become an ill-thought-out legacy
> you have to provide compatibility for later.

no worries.  I appreciate the use-case perspective a lot.  If i get
into too many details about implementation, feel free to stop me :)

holger

> Regards,
> Floris
> 
> 
> On 25 June 2012 16:23, holger krekel <holger at merlinux.eu> wrote:
> > On Mon, Jun 25, 2012 at 15:21 +0100, Floris Bruynooghe wrote:
> >> On 25 June 2012 14:29, holger krekel <holger at merlinux.eu> wrote:
> >> > On Mon, Jun 25, 2012 at 10:55 +0100, Floris Bruynooghe wrote:
> >> >> The concrete example I have now is that it could be nice in
> >> >> pytest-django to be able to request e.g. "Users" which is a model
> >> >> class used to access the User table in the database.  Currently this
> >> >> is only possible by someone explicitly defining pytest_funcarg__Users,
> >> >> but Django allows you to dynamically look up all the models in the
> >> >> database so there is no reason this can't be build automatically.
> >> >>
> >> >> I think this is what the API you proposed was for, but as I said I
> >> >> can't remember the details.  And in this case I might be less
> >> >> enthusiastic in postponing it's implementation to a later release ;-)
> >> >
> >> > It's probably true that we could invent an register-factory API for this.
> >> >
> >> > However, what about a single "models" object (done traditionally
> >> > with a pytest_funcarg__models definition) which itself provides
> >> > an API to give "Users" or others data?
> >>
> >> Yes of course, that is what I currently have in my conftest.py.  But
> >> it would still be a nice thing to be able to do and a nice example of
> >> functionality I have wished I had before.  Hence I was wondering if
> >> the API you talked about yesterday would support it.
> >
> > I guess it could, for example, look like this::
> >
> >    def pytest_configure(config):  # [1]
> >        def createmodel(name, node):
> >            """ return django model object. """
> >            # node can be None, Directory, Module, Class, Item, etc.
> >            # (code to compute model)
> >            return model
> >
> >        for name in modelnames:
> >            config.register_factory(name, createmodel)
> >
> > Getting a resource would work like this::
> >
> >    config.getresource(name)
> >
> > The "--funcargs" option would (remain) able to show the docstring
> > and location of the createmodel function.
> >
> > Another interesting bit is how to use register_factory
> > to connect the existing "pytest_funcarg__..." factories
> > which have a certain scope.  I guess something like this::
> >
> >    config.register_factory(name, factoryfunc, node)
> >
> > would suffice - it would restrict the scope of the factory
> > function to the specified node and all of its descendents.
> > It could be called from Directory, Module, Class's setup methods
> > to register the respective "pytest_funcarg__" functions scoped as
> > per-directory (conftest.py), per-module or per-class factories.
> >
> > Note that the "node" passed to the createmodel factory function
> > above is probably neccessary for this case because existing
> > funcarg-factories operate on Items (or in the future Nodes).
> >
> > getfuncargvalue() would then be implemented in terms of a
> > call to config.getresource(name, node).
> >
> > In general, register_factory needs to be callable multiple
> > times with the same name.  accept multiple factories for
> > the same resource will One little issues is that we want to
> >
> > This new resource registration/lookup could work much
> > more efficiently than the current scheme which - upon every getfuncargvalue() -
> > iterates over all plugins, modules and classes to discover matching
> > pytest_funcarg__ factories.
> >
> > hope this all makes some sense.
> >
> > best,
> > holger
> >
> >
> > [1] We really need a new hook like pytest_runtest_init() which
> >    is called once before the runtest loop actually starts it work.
> >    pytest_configure() usually works but it is also called on the
> >    xdist-master process for which setting up resources makes no sense.
> >
> >> Floris
> >>
> >> --
> >> Debian GNU/Linux -- The Power of Freedom
> >> www.debian.org | www.gnu.org | www.kernel.org
> >>
> 
> 
> 
> -- 
> Debian GNU/Linux -- The Power of Freedom
> www.debian.org | www.gnu.org | www.kernel.org
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