from hashlib import md5 import inspect from pyramid.compat import ( bytes_, getargspec, is_nonstr_iter, ) from pyramid.compat import im_func from pyramid.exceptions import ConfigurationError from pyramid.registry import predvalseq from pyramid.util import ( TopologicalSorter, action_method, ActionInfo, ) action_method = action_method # support bw compat imports ActionInfo = ActionInfo # support bw compat imports MAX_ORDER = 1 << 30 DEFAULT_PHASH = md5().hexdigest() def as_sorted_tuple(val): if not is_nonstr_iter(val): val = (val,) val = tuple(sorted(val)) return val class not_(object): """ You can invert the meaning of any predicate value by wrapping it in a call to :class:`pyramid.config.not_`. .. code-block:: python :linenos: from pyramid.config import not_ config.add_view( 'mypackage.views.my_view', route_name='ok', request_method=not_('POST') ) The above example will ensure that the view is called if the request method is *not* ``POST``, at least if no other view is more specific. This technique of wrapping a predicate value in ``not_`` can be used anywhere predicate values are accepted: - :meth:`pyramid.config.Configurator.add_view` - :meth:`pyramid.config.Configurator.add_route` - :meth:`pyramid.config.Configurator.add_subscriber` - :meth:`pyramid.view.view_config` - :meth:`pyramid.events.subscriber` .. versionadded:: 1.5 """ def __init__(self, value): self.value = value class Notted(object): def __init__(self, predicate): self.predicate = predicate def _notted_text(self, val): # if the underlying predicate doesnt return a value, it's not really # a predicate, it's just something pretending to be a predicate, # so dont update the hash if val: val = '!' + val return val def text(self): return self._notted_text(self.predicate.text()) def phash(self): return self._notted_text(self.predicate.phash()) def __call__(self, context, request): result = self.predicate(context, request) phash = self.phash() if phash: result = not result return result # under = after # over = before class PredicateList(object): def __init__(self): self.sorter = TopologicalSorter() self.last_added = None def add(self, name, factory, weighs_more_than=None, weighs_less_than=None): # Predicates should be added to a predicate list in (presumed) # computation expense order. ## if weighs_more_than is None and weighs_less_than is None: ## weighs_more_than = self.last_added or FIRST ## weighs_less_than = LAST self.last_added = name self.sorter.add( name, factory, after=weighs_more_than, before=weighs_less_than, ) def make(self, config, **kw): # Given a configurator and a list of keywords, a predicate list is # computed. Elsewhere in the code, we evaluate predicates using a # generator expression. All predicates associated with a view or # route must evaluate true for the view or route to "match" during a # request. The fastest predicate should be evaluated first, then the # next fastest, and so on, as if one returns false, the remainder of # the predicates won't need to be evaluated. # # While we compute predicates, we also compute a predicate hash (aka # phash) that can be used by a caller to identify identical predicate # lists. ordered = self.sorter.sorted() phash = md5() weights = [] preds = [] for n, (name, predicate_factory) in enumerate(ordered): vals = kw.pop(name, None) if vals is None: # XXX should this be a sentinel other than None? continue if not isinstance(vals, predvalseq): vals = (vals,) for val in vals: realval = val notted = False if isinstance(val, not_): realval = val.value notted = True pred = predicate_factory(realval, config) if notted: pred = Notted(pred) hashes = pred.phash() if not is_nonstr_iter(hashes): hashes = [hashes] for h in hashes: phash.update(bytes_(h)) weights.append(1 << n+1) preds.append(pred) if kw: raise ConfigurationError('Unknown predicate values: %r' % (kw,)) # A "order" is computed for the predicate list. An order is # a scoring. # # Each predicate is associated with a weight value. The weight of a # predicate symbolizes the relative potential "importance" of the # predicate to all other predicates. A larger weight indicates # greater importance. # # All weights for a given predicate list are bitwise ORed together # to create a "score"; this score is then subtracted from # MAX_ORDER and divided by an integer representing the number of # predicates+1 to determine the order. # # For views, the order represents the ordering in which a "multiview" # ( a collection of views that share the same context/request/name # triad but differ in other ways via predicates) will attempt to call # its set of views. Views with lower orders will be tried first. # The intent is to a) ensure that views with more predicates are # always evaluated before views with fewer predicates and b) to # ensure a stable call ordering of views that share the same number # of predicates. Views which do not have any predicates get an order # of MAX_ORDER, meaning that they will be tried very last. score = 0 for bit in weights: score = score | bit order = (MAX_ORDER - score) / (len(preds) + 1) return order, preds, phash.hexdigest() def takes_one_arg(callee, attr=None, argname=None): ismethod = False if attr is None: attr = '__call__' if inspect.isroutine(callee): fn = callee elif inspect.isclass(callee): try: fn = callee.__init__ except AttributeError: return False ismethod = hasattr(fn, '__call__') else: try: fn = getattr(callee, attr) except AttributeError: return False try: argspec = getargspec(fn) except TypeError: return False args = argspec[0] if hasattr(fn, im_func) or ismethod: # it's an instance method (or unbound method on py2) if not args: return False args = args[1:] if not args: return False if len(args) == 1: return True if argname: defaults = argspec[3] if defaults is None: defaults = () if args[0] == argname: if len(args) - len(defaults) == 1: return True return False