Miscellaneous utilities

Because repoze.what is framework-independent, its predicates can only be evaluated if you pass the WSGI environ whenever you want to evaluate them. But to makes things easier, this plugin defines utilities to evaluate predicates without passing the environ explicitly:

Predicate evaluators

With repoze.what.plugins.pylonshq.is_met(), you’ll be able to evaluate your predicates without passing the WSGI environ explicitly, as in:

>>> from repoze.what.plugins.pylonshq import is_met
>>> from repoze.what.predicates import is_user
>>> is_met(is_user('gustavo')) # Will return True if the user is "gustavo"
False

instead of:

>>> from pylons import request
>>> from repoze.what.predicates import is_user
>>> p = is_user('gustavo')
>>> p.is_met(request.environ) # Will return True if the user is "gustavo"
False

If you want to evaluate the opposite, that it’s not met, you can use not_met instead:

>>> from repoze.what.plugins.pylonshq import not_met
>>> from repoze.what.predicates import is_user
>>> not_met(is_user('gustavo')) # Will return True if the user isn't "gustavo"
True

instead of:

>>> from pylons import request
>>> from repoze.what.predicates import is_user
>>> p = is_user('gustavo')
>>> not p.is_met(request.environ) # Will return True if the user isn't "gustavo"
True

Boolean predicates

Warning

This functionality was implemented by popular demand, but it’s strongly discouraged by the author of repoze.what because it’s a monkey-patch which brings serious side-effects when enabled:

1. Third-party components which handle repoze.what predicates may get erroneous values after evaluating a predicate checker (even if they don’t use this functionality!).
2. If another non-Pylons-based application uses the same monkey-patch and you mount it on your application (or vice versa), the predicates used by both application will share the same WSGI environ.

In the two scenarios above, it will lead to serious security flaws. So avoid it by all means! Use predicate evaluators instead.

repoze.what.plugins.pylonshq.booleanize_predicates() allows you to use predicate checkers like boolean variables. Once you call it, you’ll be able to evaluate your predicates without passing the environ:

>>> from repoze.what.predicates import not_anonymous
>>> p = not_anonymous()
>>> bool(p) # Will return False if the user is anonymous; True otherwise
False

instead of:

>>> from pylons import request
>>> from repoze.what.predicates import not_anonymous
>>> p = not_anonymous()
>>> p.is_met(request.environ) # Will return False if the user is anonymous; True otherwise
False

Keep in mind that you don’t have to call this function multiple times – once is enough. For example, you could call it in the function where you set up the application in {pylonsproject}.config.middleware:

# (...)
from repoze.what.plugins.pylonshq import booleanize_predicates
# (...)

def make_app(global_conf, full_stack=True, **app_conf):
    # (...)
    booleanize_predicates()
    # (...)
    return app

Tip

If you ever need to disable this “magical” behavior, you should use repoze.what.plugins.pylonshq.debooleanize_predicates().

Note

TurboGears 2 users: TG calls this function for you, unless you disabled the default auth mechanism in {tg2application}.config.app_cfg.