e7b40242f8
This is the start of an effort to both validate that drivers fully implement the expected minimum requirements as well as to create a clear place for driver developers to learn what needs to be implemented and get documentation explaining what is expected for each method. This also enables us to create tooling for documenting the available drivers and their capabilities, to some degree. A follow up patch will show some of what I'm thinking there, but it will make it possible to write scripts for different needs. This is somewhat a cleanup attempt to the ABC work that was started a while back. This does not aim to replace that effort, but give a mechanism for some of the things expected out of that effort that ended up not being possible with how it evolved. In most cases we do not really care if a driver is inherited from a certain base class, just that it conforms to the given interface. The interface/inheritance work really centers around two separate things: * Ensuring drivers conform to an expected interface * Allowing code reuse and common implementation This is really for the first item. Additional work is needed to complete the ABC work we've done, but that really focuses on the second item, and is out of scope for the intent of this patch. Change-Id: I4168225126fe88c31712d94f0a130e9e7ede3446
106 lines
3.2 KiB
Python
106 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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import six
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def _get_arg_count(method):
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"""Get the number of args for a method.
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:param method: The method to check.
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:returns: The number of args 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.getargspec(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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@six.add_metaclass(abc.ABCMeta)
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class CinderInterface(object):
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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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