68 lines
2.5 KiB
Python
68 lines
2.5 KiB
Python
"""
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Utilities for providing backwards compatibility for the maxlength argument,
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which has been replaced by max_length, see ticket #2101.
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"""
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from warnings import warn
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def get_maxlength(self):
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return self.max_length
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def set_maxlength(self, value):
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self.max_length = value
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def legacy_maxlength(max_length, maxlength):
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"""
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Consolidates max_length and maxlength, providing backwards compatibilty
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for the legacy "maxlength" argument.
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If one of max_length or maxlength is given, then that value is returned.
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If both are given, a TypeError is raised.
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If maxlength is used at all, a deprecation warning is issued.
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"""
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if maxlength is not None:
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warn("maxlength is deprecated, use max_length instead.",
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DeprecationWarning,
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stacklevel=3)
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if max_length is not None:
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raise TypeError("field can not take both the max_length"
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" argument and the legacy maxlength argument.")
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max_length = maxlength
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return max_length
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def remove_maxlength(func):
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"""
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A decorator to be used on a class's __init__ that provides backwards
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compatibilty for the legacy "maxlength" keyword argument, i.e.
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name = models.CharField(maxlength=20)
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It does this by changing the passed "maxlength" keyword argument
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(if it exists) into a "max_length" keyword argument.
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"""
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def inner(self, *args, **kwargs):
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max_length = kwargs.get('max_length', None)
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# pop maxlength because we don't want this going to __init__.
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maxlength = kwargs.pop('maxlength', None)
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max_length = legacy_maxlength(max_length, maxlength)
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# Only set the max_length keyword argument if we got a value back.
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if max_length is not None:
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kwargs['max_length'] = max_length
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func(self, *args, **kwargs)
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return inner
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# This metaclass is used in two places, and should be removed when legacy
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# support for maxlength is dropped.
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# * oldforms.FormField
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# * db.models.fields.Field
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class LegacyMaxlength(type):
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"""
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Metaclass for providing backwards compatibility support for the
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"maxlength" keyword argument.
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"""
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def __init__(cls, name, bases, attrs):
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super(LegacyMaxlength, cls).__init__(name, bases, attrs)
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# Decorate the class's __init__ to remove any maxlength keyword.
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cls.__init__ = remove_maxlength(cls.__init__)
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# Support accessing and setting to the legacy maxlength attribute.
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cls.maxlength = property(get_maxlength, set_maxlength)
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