70 lines
2.4 KiB
Python
70 lines
2.4 KiB
Python
from django.core.exceptions import ObjectDoesNotExist
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from django.db import models
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class MergeException(Exception):
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pass
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class OneToOneConflict(MergeException):
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pass
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ERROR = 0
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KEEP = 1
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DELETE = 2
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def merge(from_obj, to_obj, one_to_one_conflict=ERROR):
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if not isinstance(from_obj, type(to_obj)):
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raise ValueError("both objects must be of the same type")
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if from_obj.pk == to_obj.pk:
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raise ValueError("cannot merge object with itself")
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for related in from_obj._meta.get_all_related_objects():
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accessor_name = related.get_accessor_name()
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varname = related.field.name
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# in Django 1.8 can test for related.one_to_one
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if isinstance(related.field, models.OneToOneField):
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try:
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field = getattr(from_obj, accessor_name)
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try:
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to_field = getattr(to_obj, accessor_name)
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if one_to_one_conflict == KEEP:
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pass # do nothing
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elif one_to_one_conflict == DELETE:
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to_field.delete()
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setattr(field, varname, to_obj)
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field.save()
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else:
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raise OneToOneConflict(
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"both fields have an attribute set for {}".format(accessor_name))
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except ObjectDoesNotExist:
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# doesn't exist, safe to overwrite
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setattr(field, varname, to_obj)
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field.save()
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except ObjectDoesNotExist:
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# from_obj one to one isn't set, skip
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pass
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# in Django 1.8 can test for related.multiple
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elif isinstance(related.field, models.ForeignKey):
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field = getattr(from_obj, accessor_name)
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field.all().update(**{varname: to_obj})
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else:
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raise NotImplementedError('unexpected relation type, please file a bug')
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for related in from_obj._meta.get_all_related_many_to_many_objects():
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accessor_name = related.get_accessor_name()
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varname = related.field.name
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if not accessor_name:
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# not set in M2M to self, but varname will match
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accessor_name = varname
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field = getattr(from_obj, accessor_name)
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for f in field.all():
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getattr(f, varname).remove(from_obj)
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getattr(f, varname).add(to_obj)
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