139 lines
5.0 KiB
Python
139 lines
5.0 KiB
Python
# Licensed under the Apache License, Version 2.0 (the "License"); you may
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# not use this file except in compliance with the License. You may obtain
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# a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS, WITHOUT
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# WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. See the
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# License for the specific language governing permissions and limitations
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# under the License.
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"""
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NOTE: This module shall not be used by external projects. It will be moved
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to neutron-lib in due course, and then it can be used from there.
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"""
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import collections
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import inspect
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from neutron_lib.utils import helpers
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# This dictionary will store methods for extending API resources.
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# Extensions can add their own methods by invoking register_funcs().
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_resource_extend_functions = {
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# <resource1> : [<func1>, <func2>, ...],
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# <resource2> : [<func1>, <func2>, ...],
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# ...
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}
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# This dictionary will store @extends decorated methods with a list of
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# resources that each method will extend on class initialization.
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_DECORATED_EXTEND_METHODS = collections.defaultdict(list)
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def register_funcs(resource, funcs):
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"""Add functions to extend a resource.
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:param resource: A resource collection name.
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:type resource: str
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:param funcs: A list of functions.
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:type funcs: list of callable
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These functions take a resource dict and a resource object and
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update the resource dict with extension data (possibly retrieved
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from the resource db object).
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def _extend_foo_with_bar(foo_res, foo_db):
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foo_res['bar'] = foo_db.bar_info # example
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return foo_res
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"""
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funcs = [helpers.make_weak_ref(f) if callable(f) else f
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for f in funcs]
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_resource_extend_functions.setdefault(resource, []).extend(funcs)
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def get_funcs(resource):
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"""Retrieve a list of functions extending a resource.
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:param resource: A resource collection name.
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:type resource: str
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:return: A list (possibly empty) of functions extending resource.
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:rtype: list of callable
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"""
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return _resource_extend_functions.get(resource, [])
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def apply_funcs(resource_type, response, db_object):
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for func in get_funcs(resource_type):
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resolved_func = helpers.resolve_ref(func)
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if resolved_func:
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resolved_func(response, db_object)
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def extends(resources):
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"""Use to decorate methods on classes before initialization.
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Any classes that use this must themselves be decorated with the
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@has_resource_extenders decorator to setup the __new__ method to
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actually register the instance methods after initialization.
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:param resources: Resource collection names. The decorated method will
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be registered with each resource as an extend function.
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:type resources: list of str
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"""
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def decorator(method):
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_DECORATED_EXTEND_METHODS[method].extend(resources)
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return method
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return decorator
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def has_resource_extenders(klass):
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"""Decorator to setup __new__ method in classes to extend resources.
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Any method decorated with @extends above is an unbound method on a class.
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This decorator sets up the class __new__ method to add the bound
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method to _resource_extend_functions after object instantiation.
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"""
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orig_new = klass.__new__
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new_inherited = '__new__' not in klass.__dict__
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@staticmethod
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def replacement_new(cls, *args, **kwargs):
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if new_inherited:
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# class didn't define __new__ so we need to call inherited __new__
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super_new = super(klass, cls).__new__
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if super_new is object.__new__:
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# object.__new__ doesn't accept args nor kwargs
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instance = super_new(cls)
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else:
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instance = super_new(cls, *args, **kwargs)
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else:
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instance = orig_new(cls, *args, **kwargs)
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if getattr(instance, '_DECORATED_METHODS_REGISTERED', False):
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# Avoid running this logic twice for classes inheriting other
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# classes with this same decorator. Only one needs to execute
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# to subscribe all decorated methods.
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return instance
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for name, unbound_method in inspect.getmembers(cls):
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if (not inspect.ismethod(unbound_method) and
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not inspect.isfunction(unbound_method)):
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continue
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# Handle py27/py34 difference
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method = getattr(unbound_method, 'im_func', unbound_method)
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if method not in _DECORATED_EXTEND_METHODS:
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continue
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for resource in _DECORATED_EXTEND_METHODS[method]:
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# Register the bound method for the resourse
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register_funcs(resource, [method])
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setattr(instance, '_DECORATED_METHODS_REGISTERED', True)
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return instance
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klass.__new__ = replacement_new
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return klass
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