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util.py
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util.py
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import pkg_resources
import sys
import weakref
from pyramid.exceptions import ConfigurationError
from pyramid.path import package_of
class DottedNameResolver(object):
""" This class resolves dotted name references to 'global' Python
objects (objects which can be imported) to those objects.
Two dotted name styles are supported during deserialization:
- ``pkg_resources``-style dotted names where non-module attributes
of a package are separated from the rest of the path using a ':'
e.g. ``package.module:attr``.
- ``zope.dottedname``-style dotted names where non-module
attributes of a package are separated from the rest of the path
using a '.' e.g. ``package.module.attr``.
These styles can be used interchangeably. If the serialization
contains a ``:`` (colon), the ``pkg_resources`` resolution
mechanism will be chosen, otherwise the ``zope.dottedname``
resolution mechanism will be chosen.
The constructor accepts a single argument named ``package`` which
should be a one of:
- a Python module or package object
- A fully qualified (not relative) dotted name to a module or package
- The value ``None``
The ``package`` is used when relative dotted names are supplied to
the resolver's ``resolve`` and ``maybe_resolve`` methods. A
dotted name which has a ``.`` (dot) or ``:`` (colon) as its first
character is treated as relative.
If the value ``None`` is supplied as the package name, the
resolver will only be able to resolve fully qualified (not
relative) names. Any attempt to resolve a relative name when the
``package`` is ``None`` will result in an
:exc:`pyramid.config.ConfigurationError` exception.
If a *module* or *module name* (as opposed to a package or package
name) is supplied as ``package``, its containing package is
computed and this package used to derive the package name (all
names are resolved relative to packages, never to modules). For
example, if the ``package`` argument to this type was passed the
string ``xml.dom.expatbuilder``, and ``.mindom`` is supplied to
the ``resolve`` method, the resulting import would be for
``xml.minidom``, because ``xml.dom.expatbuilder`` is a module
object, not a package object.
If a *package* or *package name* (as opposed to a module or module
name) is supplied as ``package``, this package will be used to
relative compute dotted names. For example, if the ``package``
argument to this type was passed the string ``xml.dom``, and
``.minidom`` is supplied to the ``resolve`` method, the resulting
import would be for ``xml.minidom``.
When a dotted name cannot be resolved, a
:class:`pyramid.exceptions.ConfigurationError` error is raised.
"""
def __init__(self, package):
if package is None:
self.package_name = None
self.package = None
else:
if isinstance(package, basestring):
try:
__import__(package)
except ImportError:
raise ConfigurationError(
'The dotted name %r cannot be imported' % (package,))
package = sys.modules[package]
self.package = package_of(package)
self.package_name = self.package.__name__
def _pkg_resources_style(self, value):
""" package.module:attr style """
if value.startswith('.') or value.startswith(':'):
if not self.package_name:
raise ConfigurationError(
'relative name %r irresolveable without '
'package_name' % (value,))
if value in ['.', ':']:
value = self.package_name
else:
value = self.package_name + value
return pkg_resources.EntryPoint.parse(
'x=%s' % value).load(False)
def _zope_dottedname_style(self, value):
""" package.module.attr style """
module = self.package_name
if not module:
module = None
if value == '.':
if module is None:
raise ConfigurationError(
'relative name %r irresolveable without package' % (value,)
)
name = module.split('.')
else:
name = value.split('.')
if not name[0]:
if module is None:
raise ConfigurationError(
'relative name %r irresolveable without '
'package' % (value,)
)
module = module.split('.')
name.pop(0)
while not name[0]:
module.pop()
name.pop(0)
name = module + name
used = name.pop(0)
found = __import__(used)
for n in name:
used += '.' + n
try:
found = getattr(found, n)
except AttributeError:
__import__(used)
found = getattr(found, n) # pragma: no cover
return found
def resolve(self, dotted):
if not isinstance(dotted, basestring):
raise ConfigurationError('%r is not a string' % (dotted,))
return self.maybe_resolve(dotted)
def maybe_resolve(self, dotted):
if isinstance(dotted, basestring):
if ':' in dotted:
return self._pkg_resources_style(dotted)
else:
return self._zope_dottedname_style(dotted)
return dotted
class WeakOrderedSet(object):
""" Maintain a set of items.
Each item is stored as a weakref to avoid extending their lifetime.
The values may be iterated over or the last item added may be
accessed via the ``last`` property.
"""
def __init__(self):
self._items = {}
self._order = []
def add(self, item):
""" Add an item to the set."""
oid = id(item)
if oid in self._items:
return
ref = weakref.ref(item, lambda x: self.remove(item))
self._items[oid] = ref
self._order.append(oid)
def remove(self, item):
""" Remove an item from the set."""
oid = id(item)
if oid in self._items:
del self._items[oid]
self._order.remove(oid)
def empty(self):
""" Clear all objects from the set."""
self._items = {}
self._order = []
def __len__(self):
return len(self._order)
def __contains__(self, item):
oid = id(item)
return oid in self._items
def __iter__(self):
return (self._items[oid]() for oid in self._order)
@property
def last(self):
if self._order:
oid = self._order[-1]
return self._items[oid]()