[py-dev] RFC: draft new resource management API (v1)

Ronny Pfannschmidt Ronny.Pfannschmidt at gmx.de
Wed Jun 27 18:32:53 CEST 2012

i noticed that there is no way to name items in those lists

On 06/27/2012 06:15 PM, holger krekel wrote:
> On Wed, Jun 27, 2012 at 08:43 -0600, Carl Meyer wrote:
>> I like it! In particular the parametrization support by passing a list
>> is a quite intuitive extension of the API.
>> "atnode" seems like an opaque arg name - what's wrong with "scope"? The
>> latter name seems more intuitive to me. Would this arg have a default value?
> "scope" makes sense - it's just that in the current API scope is a
> "class", "module", ... string.  Existing users might easily get a bit of
> type clash - especially if you have a mixed funcarg/resource scenario.
> Maybe "scopenode"?
> The default scopenode would be the one on which you are calling
> "register_factory".  So in the first documented example call:
>      session.register_factory("db", createdb, scopenode=session)
> the "scopenode" call would actually be superfluous.  (Sidenote: the session
> object is also a node - the root node from which all collection and item
> nodes are descendants.  Each node has a ".session" reference back to this
> root node).
>> In the long run, if funcarg-style is considered a useful shortcut and
>> will not be deprecated, it would be nice if there were a bit more naming
>> and API consistency between funcarg-style and new-style resource
>> handling -- it would make them feel more aspects of one system rather
>> than two different systems. I think this would really just require
>> switching from pytest_funcarg__foo to pytest_resource__foo, renaming
>> cached_setup to register_factory (and having it use the same API), and
>> renaming getfuncargvalue to getresource. Of course I don't know whether
>> this consistency is really worth the backwards-compatibility/deprecation
>> hassles.
> * getresource/getfuncargvalue: makes sense to me to go for advertising and
>    documenting getresource() instead of getfuncargvalue() and keeping
>    the latter as an alias with or without deprecation.
> * addfinalizer would remain unmodified - it's just that the "request"
>    object passed to funcarg-factories adds finalizers with test function
>    invocation scope, whereas node.addfinalizer() does it for the respective
>    node scope (so e.g. called from a Class node it would register a per-class
>    finalizer)
> * cached_setup: i hope that we do not need to offer this method anymore
>    other than for compatibility.  It's internal caching-key is not easy
>    to explain and more than once users have stumbled about understanding it.
>    cached_setup is required as long as pytest_funcarg__ factories are called
>    _each_ time a resource is requested. (By contrast the new getresource()
>    only triggers a factory call once for the registered scope - thus
>    the factory implementation itself does not need to care for caching).
>    Note that register_factory is a different beast than cached_setup:
>    it does not create a value, just registers a factory. So i don't see
>    how we can unify this.
> As to a possible resource-factory auto-discovery, i can imagine it to
> work with introducing a marker::
>      # example content in a test module or in a conftest.py file
>      @pytest.mark.resourcefactory("db", scope=pytest.Class)
>      def myfactory(name, node):
>          # factory called once per each requesting class (methods
>          # on this class will share the returned value)
> this declaration would trigger a register_factory("db", myfactory) call.
> If we want to extend this to parametrization (multiple db factories)
> we probably need something like this::
>      @pytest.mark.resourcefactory("db", scope=pytest.Class, multi=True)
>      def make_db_factories(name, node):
>          factoryfuncs = [compute list of factory funcs]
>          return factoryfuncs
> This would be called at collection time and the scope and the number
> of to-be-created values would be known in advance.  It's basically
> equivalent to a classnode.register_factory([list of factory funcs]) call.
> (we could auto-magically recognize yield-generating functions but i'd
> like to avoid it).
> To go the full circle, the signature of factory functions could rather
> accept a "request" object instead of (name, node). Actually today, a
> request object has this internal state anyway. pytest_funcarg__ would thus
> only look slighly special in that it skips the marker and has a fixed scope
> of "pytest.Function".
> Hope this thought train makes some sense :)
> holger
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