60 lines
2.0 KiB
Python
60 lines
2.0 KiB
Python
from importlib import import_module
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from django.utils.version import get_docs_version
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def deconstructible(*args, path=None):
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"""
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Class decorator that allows the decorated class to be serialized
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by the migrations subsystem.
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The `path` kwarg specifies the import path.
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"""
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def decorator(klass):
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def __new__(cls, *args, **kwargs):
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# We capture the arguments to make returning them trivial
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obj = super(klass, cls).__new__(cls)
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obj._constructor_args = (args, kwargs)
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return obj
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def deconstruct(obj):
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"""
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Return a 3-tuple of class import path, positional arguments,
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and keyword arguments.
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"""
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# Fallback version
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if path and type(obj) is klass:
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module_name, _, name = path.rpartition(".")
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else:
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module_name = obj.__module__
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name = obj.__class__.__name__
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# Make sure it's actually there and not an inner class
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module = import_module(module_name)
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if not hasattr(module, name):
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raise ValueError(
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"Could not find object %s in %s.\n"
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"Please note that you cannot serialize things like inner "
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"classes. Please move the object into the main module "
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"body to use migrations.\n"
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"For more information, see "
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"https://docs.djangoproject.com/en/%s/topics/migrations/"
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"#serializing-values" % (name, module_name, get_docs_version())
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)
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return (
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path
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if path and type(obj) is klass
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else f"{obj.__class__.__module__}.{name}",
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obj._constructor_args[0],
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obj._constructor_args[1],
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)
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klass.__new__ = staticmethod(__new__)
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klass.deconstruct = deconstruct
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return klass
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if not args:
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return decorator
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return decorator(*args)
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