103 lines
3.2 KiB
Python
103 lines
3.2 KiB
Python
# Copyright 2016 Dell Inc.
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# All Rights Reserved.
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#
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# 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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import abc
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import inspect
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def _get_arg_count(method):
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"""Get the number of positional parameters for a method.
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:param method: The method to check.
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:returns: The number of positional parameters for the method.
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"""
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if not method:
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return 0
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arg_spec = inspect.getfullargspec(method)
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return len(arg_spec[0])
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def _get_method_info(cls):
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"""Get all methods defined in a class.
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Note: This will only return public methods and their associated arg count.
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:param cls: The class to inspect.
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:returns: `Dict` of method names with a tuple of the method and their arg
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counts.
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"""
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result = {}
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methods = inspect.getmembers(cls, inspect.ismethod)
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for (name, method) in methods:
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if name.startswith('_'):
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# Skip non-public methods
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continue
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result[name] = (method, _get_arg_count(method))
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return result
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class CinderInterface(object, metaclass=abc.ABCMeta):
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"""Interface base class for Cinder.
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Cinder interfaces should inherit from this class to support indirect
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inheritance evaluation.
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This can be used to validate compliance to an interface without requiring
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that the class actually be inherited from the same base class.
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"""
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_method_cache = None
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@classmethod
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def _get_methods(cls):
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if not cls._method_cache:
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cls._method_cache = _get_method_info(cls)
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return cls._method_cache
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@classmethod
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def __subclasshook__(cls, other_cls):
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"""Custom class inheritance evaluation.
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:param cls: The CinderInterface to check against.
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:param other_cls: The class to be checked if it implements
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our interface.
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"""
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interface_methods = cls._get_methods()
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driver_methods = _get_method_info(other_cls)
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interface_keys = interface_methods.keys()
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driver_keys = driver_methods.keys()
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matching_count = len(set(interface_keys) & set(driver_keys))
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if matching_count != len(interface_keys):
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# Missing some methods, does not implement this interface or is
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# missing something.
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return NotImplemented
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# TODO(smcginnis) Add method signature checking.
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# We know all methods are there, now make sure they look right.
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# Unfortunately the methods can be obfuscated by certain decorators,
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# so we need to find a better way to pull out the real method
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# signatures.
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# driver_methods[method_name][0].func_closure.cell_contents works
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# for most cases but not all.
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# AST might work instead of using introspect.
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return True
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