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https://github.com/avatao-content/baseimage-tutorial-framework
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Add metaclass capable of building instances from class name string
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from .type_id_registry import TypeIdREgistryMixin
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import pytest
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from .type_id_registry import TypeIdREgistryMixin
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def test_registry():
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class A(TypeIdREgistryMixin):
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_type_id_registry = {}
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class B(A):
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pass
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class C(A):
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pass
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# pylint: disable=protected-access
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assert A._type_id_registry['B'] == B
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assert A._type_id_registry['C'] == C
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def test_build_by_type_id():
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class D(TypeIdREgistryMixin):
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_type_id_registry = {}
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built = []
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class E(D):
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def __init__(self):
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built.append(self)
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class F(D):
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def __init__(self):
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built.append(self)
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raise RuntimeError('cica')
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class H(E):
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pass
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D.build_type('E')
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assert isinstance(built[0], E)
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with pytest.raises(RuntimeError) as err:
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D.build_type('F')
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assert err.value.args[0] == 'cica'
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assert isinstance(built[1], F)
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D.build_type('H')
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assert isinstance(built[2], H)
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assert isinstance(built[2], E)
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from abc import ABCMeta
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from contextlib import suppress
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class TypeIdREgistryMeta(ABCMeta):
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def __init__(cls, name, bases, attrs):
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with suppress(AttributeError):
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if cls.__name__ in cls._type_id_registry:
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raise RuntimeError('Type id must be unique!')
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cls._type_id_registry[cls.__name__] = cls
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super().__init__(name, bases, attrs)
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class TypeIdREgistryMixin(metaclass=TypeIdREgistryMeta):
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@classmethod
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def build_type(cls, type_id, *args, **kwargs):
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try:
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instance_type = cls._type_id_registry[type_id]
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return instance_type(*args, **kwargs)
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except KeyError:
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raise RuntimeError(f'No type with id {type_id}!')
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