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130 lines
4.4 KiB
Python
130 lines
4.4 KiB
Python
"""
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Helper function for returning the field information that is associated
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with a model class. This includes returning all the forward and reverse
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relationships and their associated metadata.
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Usage: `get_field_info(model)` returns a `FieldInfo` instance.
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"""
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from collections import namedtuple
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from django.db import models
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from django.utils import six
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from rest_framework.compat import OrderedDict
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import inspect
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FieldInfo = namedtuple('FieldResult', [
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'pk', # Model field instance
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'fields', # Dict of field name -> model field instance
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'forward_relations', # Dict of field name -> RelationInfo
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'reverse_relations', # Dict of field name -> RelationInfo
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'fields_and_pk', # Shortcut for 'pk' + 'fields'
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'relations' # Shortcut for 'forward_relations' + 'reverse_relations'
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])
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RelationInfo = namedtuple('RelationInfo', [
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'model_field',
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'related',
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'to_many',
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'has_through_model'
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])
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def _resolve_model(obj):
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"""
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Resolve supplied `obj` to a Django model class.
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`obj` must be a Django model class itself, or a string
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representation of one. Useful in situtations like GH #1225 where
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Django may not have resolved a string-based reference to a model in
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another model's foreign key definition.
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String representations should have the format:
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'appname.ModelName'
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"""
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if isinstance(obj, six.string_types) and len(obj.split('.')) == 2:
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app_name, model_name = obj.split('.')
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return models.get_model(app_name, model_name)
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elif inspect.isclass(obj) and issubclass(obj, models.Model):
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return obj
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raise ValueError("{0} is not a Django model".format(obj))
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def get_field_info(model):
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"""
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Given a model class, returns a `FieldInfo` instance containing metadata
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about the various field types on the model.
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"""
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opts = model._meta.concrete_model._meta
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# Deal with the primary key.
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pk = opts.pk
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while pk.rel and pk.rel.parent_link:
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# If model is a child via multitable inheritance, use parent's pk.
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pk = pk.rel.to._meta.pk
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# Deal with regular fields.
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fields = OrderedDict()
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for field in [field for field in opts.fields if field.serialize and not field.rel]:
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fields[field.name] = field
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# Deal with forward relationships.
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forward_relations = OrderedDict()
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for field in [field for field in opts.fields if field.serialize and field.rel]:
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forward_relations[field.name] = RelationInfo(
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model_field=field,
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related=_resolve_model(field.rel.to),
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to_many=False,
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has_through_model=False
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)
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# Deal with forward many-to-many relationships.
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for field in [field for field in opts.many_to_many if field.serialize]:
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forward_relations[field.name] = RelationInfo(
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model_field=field,
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related=_resolve_model(field.rel.to),
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to_many=True,
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has_through_model=(
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not field.rel.through._meta.auto_created
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)
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)
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# Deal with reverse relationships.
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reverse_relations = OrderedDict()
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for relation in opts.get_all_related_objects():
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accessor_name = relation.get_accessor_name()
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reverse_relations[accessor_name] = RelationInfo(
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model_field=None,
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related=relation.model,
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to_many=relation.field.rel.multiple,
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has_through_model=False
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)
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# Deal with reverse many-to-many relationships.
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for relation in opts.get_all_related_many_to_many_objects():
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accessor_name = relation.get_accessor_name()
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reverse_relations[accessor_name] = RelationInfo(
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model_field=None,
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related=relation.model,
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to_many=True,
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has_through_model=(
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(getattr(relation.field.rel, 'through', None) is not None)
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and not relation.field.rel.through._meta.auto_created
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)
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)
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# Shortcut that merges both regular fields and the pk,
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# for simplifying regular field lookup.
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fields_and_pk = OrderedDict()
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fields_and_pk['pk'] = pk
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fields_and_pk[pk.name] = pk
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fields_and_pk.update(fields)
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# Shortcut that merges both forward and reverse relationships
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relations = OrderedDict(
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list(forward_relations.items()) +
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list(reverse_relations.items())
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)
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return FieldInfo(pk, fields, forward_relations, reverse_relations, fields_and_pk, relations)
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