54 lines
2.2 KiB
Python
54 lines
2.2 KiB
Python
from collections import namedtuple
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from django.db.models.fields.related import RECURSIVE_RELATIONSHIP_CONSTANT
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def is_referenced_by_foreign_key(state, model_name_lower, field, field_name):
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for state_app_label, state_model in state.models:
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for _, f in state.models[state_app_label, state_model].fields:
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if (f.related_model and
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'%s.%s' % (state_app_label, model_name_lower) == f.related_model.lower() and
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hasattr(f, 'to_fields')):
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if (f.to_fields[0] is None and field.primary_key) or field_name in f.to_fields:
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return True
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return False
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class ModelTuple(namedtuple('ModelTupleBase', ('app_label', 'model_name'))):
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@classmethod
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def from_model(cls, model, app_label=None, model_name=None):
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"""
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Take a model class or a 'app_label.ModelName' string and return a
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ModelTuple('app_label', 'modelname'). The optional app_label and
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model_name arguments are the defaults if "self" or "ModelName" are
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passed.
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"""
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if isinstance(model, str):
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if model == RECURSIVE_RELATIONSHIP_CONSTANT:
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return cls(app_label, model_name)
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if '.' in model:
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return cls(*model.lower().split('.', 1))
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return cls(app_label, model.lower())
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return cls(model._meta.app_label, model._meta.model_name)
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def __eq__(self, other):
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if isinstance(other, ModelTuple):
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# Consider ModelTuple equal if their model_name is equal and either
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# one of them is missing an app_label.
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return self.model_name == other.model_name and (
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self.app_label is None or other.app_label is None or self.app_label == other.app_label
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)
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return super().__eq__(other)
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def field_references_model(field, model_tuple):
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"""Return whether or not field references model_tuple."""
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remote_field = field.remote_field
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if remote_field:
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if ModelTuple.from_model(remote_field.model) == model_tuple:
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return True
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through = getattr(remote_field, 'through', None)
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if through and ModelTuple.from_model(through) == model_tuple:
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return True
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return False
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