"""Provides Registry mapping utility."""
from testplan.common.utils import logger
[docs]class Registry(logger.Loggable):
"""
A utility that provides a decorator (`@registry.bind`) for
mapping objects to another (decorated) class.
Supports absolute or category based
defaults via `@registry.bind_default` decorator as well.
Example:
>>> registry = Registry()
>>> class ClassA:
... pass
>>> # instances of ClassA are now bound to ClassB for this registry
>>> @registry.bind(ClassA)
>>> class ClassB:
... pass
>>> obj_a = ClassA()
>>> registry[obj_a] is ClassB
... True
"""
def __init__(self):
self.data = {}
self._default = None
self._category_defaults = {}
super(Registry, self).__init__()
@property
def default(self):
return self._default
@default.setter
def default(self, value):
if self._default is not None:
raise ValueError(
"Cannot re-bind default value. (Existing: {})".format(
self.default
)
)
self._default = value
[docs] def get_lookup_key(self, obj):
"""
This method is used for generating the key when do a lookup
from the registry. Object class is used by default.
"""
return obj.__class__
[docs] def get_record_key(self, obj):
"""
This method is used for generating the key when we bind
an object (possibly a class) via the registry.
"""
return obj
[docs] def get_category(self, obj):
"""
Override this to define logic for generating
the category key from the object instance.
"""
try:
return getattr(obj, "category", obj["category"])
except KeyError:
# User has registered defaults for a category
# however category retrieval from object failed
# Need to fail explicitly and warn the user
if self._category_defaults:
raise NotImplementedError(
"Could not retrieve category information from: {}."
"You may need to override `get_category`"
"of the registry.".format(obj)
)
raise
def _get_default(self, obj):
try:
return self._category_defaults[self.get_category(obj)]
except KeyError:
if self._default:
return self._default
raise KeyError("No mapping found for: {}".format(obj))
def __getitem__(self, item):
try:
return self.data[self.get_lookup_key(item)]
except KeyError:
return self._get_default(item)
def __setitem__(self, key, value):
key = self.get_record_key(key)
self.data[key] = value
[docs] def bind(self, *classes):
"""
Decorator for binding one or more classes to another.
:param classes: One or more classes that
will be bound to the decorated class.
"""
def wrapper(value):
for kls in classes:
self[kls] = value
return value
return wrapper
[docs] def bind_default(self, category=None):
"""
Decorator for binding a class as category based or absolute default.
:param category: (optional) If provided, the decorated class will
be the default for the given category, otherwise
it will be the absolute default.
"""
def wrapper(value):
if category:
if category in self._category_defaults:
raise ValueError(
"Cannot overwrite default value "
"for category: {}".format(category)
)
self._category_defaults[category] = value
else:
self.default = value
return value
return wrapper