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""" Helper function for returning the field information that is associated with a model class. This includes returning all the forward and reverse relationships and their associated metadata. Usage: `get_field_info(model)` returns a `FieldInfo` instance. """ from collections import OrderedDict, namedtuple FieldInfo = namedtuple('FieldResult', [ 'pk', # Model field instance 'fields', # Dict of field name -> model field instance 'forward_relations', # Dict of field name -> RelationInfo 'reverse_relations', # Dict of field name -> RelationInfo 'fields_and_pk', # Shortcut for 'pk' + 'fields' 'relations' # Shortcut for 'forward_relations' + 'reverse_relations' ]) RelationInfo = namedtuple('RelationInfo', [ 'model_field', 'related_model', 'to_many', 'to_field', 'has_through_model', 'reverse' ]) def get_field_info(model): """ Given a model class, returns a `FieldInfo` instance, which is a `namedtuple`, containing metadata about the various field types on the model including information about their relationships. """ opts = model._meta.concrete_model._meta pk = _get_pk(opts) fields = _get_fields(opts) forward_relations = _get_forward_relationships(opts) reverse_relations = _get_reverse_relationships(opts) fields_and_pk = _merge_fields_and_pk(pk, fields) relationships = _merge_relationships(forward_relations, reverse_relations) return FieldInfo(pk, fields, forward_relations, reverse_relations, fields_and_pk, relationships) def _get_pk(opts): pk = opts.pk rel = pk.remote_field while rel and rel.parent_link: # If model is a child via multi-table inheritance, use parent's pk. pk = pk.remote_field.model._meta.pk rel = pk.remote_field return pk def _get_fields(opts): fields = OrderedDict() for field in [field for field in opts.fields if field.serialize and not field.remote_field]: fields[field.name] = field return fields def _get_to_field(field): return getattr(field, 'to_fields', None) and field.to_fields[0] def _get_forward_relationships(opts): """ Returns an `OrderedDict` of field names to `RelationInfo`. """ forward_relations = OrderedDict() for field in [field for field in opts.fields if field.serialize and field.remote_field]: forward_relations[field.name] = RelationInfo( model_field=field, related_model=field.remote_field.model, to_many=False, to_field=_get_to_field(field), has_through_model=False, reverse=False ) # Deal with forward many-to-many relationships. for field in [field for field in opts.many_to_many if field.serialize]: forward_relations[field.name] = RelationInfo( model_field=field, related_model=field.remote_field.model, to_many=True, # manytomany do not have to_fields to_field=None, has_through_model=( not field.remote_field.through._meta.auto_created ), reverse=False ) return forward_relations def _get_reverse_relationships(opts): """ Returns an `OrderedDict` of field names to `RelationInfo`. """ reverse_relations = OrderedDict() all_related_objects = [r for r in opts.related_objects if not r.field.many_to_many] for relation in all_related_objects: accessor_name = relation.get_accessor_name() reverse_relations[accessor_name] = RelationInfo( model_field=None, related_model=relation.related_model, to_many=relation.field.remote_field.multiple, to_field=_get_to_field(relation.field), has_through_model=False, reverse=True ) # Deal with reverse many-to-many relationships. all_related_many_to_many_objects = [r for r in opts.related_objects if r.field.many_to_many] for relation in all_related_many_to_many_objects: accessor_name = relation.get_accessor_name() reverse_relations[accessor_name] = RelationInfo( model_field=None, related_model=relation.related_model, to_many=True, # manytomany do not have to_fields to_field=None, has_through_model=( (getattr(relation.field.remote_field, 'through', None) is not None) and not relation.field.remote_field.through._meta.auto_created ), reverse=True ) return reverse_relations def _merge_fields_and_pk(pk, fields): fields_and_pk = OrderedDict() fields_and_pk['pk'] = pk fields_and_pk[pk.name] = pk fields_and_pk.update(fields) return fields_and_pk def _merge_relationships(forward_relations, reverse_relations): return OrderedDict( list(forward_relations.items()) + list(reverse_relations.items()) ) def is_abstract_model(model): """ Given a model class, returns a boolean True if it is abstract and False if it is not. """ return hasattr(model, '_meta') and hasattr(model._meta, 'abstract') and model._meta.abstract