82 lines
2.4 KiB
Python
82 lines
2.4 KiB
Python
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import warnings
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from django.core import checks
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from django.utils.deprecation import RemovedInDjango60Warning
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from django.utils.functional import cached_property
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NOT_PROVIDED = object()
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class FieldCacheMixin:
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"""
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An API for working with the model's fields value cache.
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Subclasses must set self.cache_name to a unique entry for the cache -
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typically the field’s name.
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"""
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# RemovedInDjango60Warning.
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def get_cache_name(self):
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raise NotImplementedError
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@cached_property
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def cache_name(self):
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# RemovedInDjango60Warning: when the deprecation ends, replace with:
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# raise NotImplementedError
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cache_name = self.get_cache_name()
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warnings.warn(
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f"Override {self.__class__.__qualname__}.cache_name instead of "
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"get_cache_name().",
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RemovedInDjango60Warning,
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stacklevel=3,
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)
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return cache_name
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def get_cached_value(self, instance, default=NOT_PROVIDED):
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try:
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return instance._state.fields_cache[self.cache_name]
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except KeyError:
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if default is NOT_PROVIDED:
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raise
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return default
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def is_cached(self, instance):
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return self.cache_name in instance._state.fields_cache
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def set_cached_value(self, instance, value):
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instance._state.fields_cache[self.cache_name] = value
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def delete_cached_value(self, instance):
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del instance._state.fields_cache[self.cache_name]
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class CheckFieldDefaultMixin:
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_default_hint = ("<valid default>", "<invalid default>")
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def _check_default(self):
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if (
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self.has_default()
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and self.default is not None
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and not callable(self.default)
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):
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return [
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checks.Warning(
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"%s default should be a callable instead of an instance "
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"so that it's not shared between all field instances."
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% (self.__class__.__name__,),
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hint=(
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"Use a callable instead, e.g., use `%s` instead of "
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"`%s`." % self._default_hint
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),
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obj=self,
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id="fields.E010",
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)
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]
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else:
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return []
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def check(self, **kwargs):
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errors = super().check(**kwargs)
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errors.extend(self._check_default())
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return errors
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