collection_class=set is not supported

[ptallada]

Hi!

I have a model with some relationships configured with collection_class=set.
But when I try to insert a new record it tries to call the constructor with the collection as a list, and that fails with following error.

A workaround is to override the class constructor. But maybe it is better if pyramid_sacrud could cast the iterable to the collection_class type.

Traceback (most recent call last):
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/pyramid_sacrud/views/CRUD.py", line 140, in sa_add
obj = self.crud.create(data)
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sacrud/action.py", line 66, in create
return self._add(obj, data, **kwargs)
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sacrud/action.py", line 183, in _add
.add(self.session, data, self.table)
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sacrud/preprocessing.py", line 206, in add
return self.obj(**params)
File "", line 4, in init
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/state.py", line 269, in _initialize_instance
return manager.original_init(_mixed[1:], *_kwargs)
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/ext/declarative/base.py", line 526, in _declarative_constructor
setattr(self, k, kwargs[k])
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/attributes.py", line 226, in set
instance_dict(instance), value, None)
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/attributes.py", line 1009, in set
lambda adapter, i: adapter.adapt_like_to_iterable(i))
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/attributes.py", line 1025, in _set_iterable
new_values = list(adapter(new_collection, iterable))
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/attributes.py", line 1009, in
lambda adapter, i: adapter.adapt_like_to_iterable(i))
File "/home/tallada/Projectes/env/cosmohub_v5/local/lib/python2.7/site-packages/sqlalchemy/orm/collections.py", line 646, in adapt_like_to_iterable
given, wanted))
TypeError: Incompatible collection type: list is not set-like

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[ptallada]

Quick fix in preprocessing.py, checking if the collection_class attribute is defined and using it to wrap the list.

Lines 55-58:

if relation.property.collection_class:
    return relation.property.collection_class(objs.all())
else:
    return objs.all()

[uralbash]

@ptallada Thanks!
This is a very special case, it works quite as shown below:

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class Item(Base):
    __tablename__ = 'item'
    id = Column(Integer, primary_key=True)
    notes = relationship("Note",
                collection_class=set,
                cascade="all, delete-orphan")


class Note(Base):
    __tablename__ = 'note'
    id = Column(Integer, primary_key=True)
    item_id = Column(Integer, ForeignKey('item.id'), nullable=False)
    keyword = Column(String)
    text = Column(String)

    def __init__(self, keyword, text):
        self.keyword = keyword
        self.text = text

item = Item()
note = Note("foo", "bar")
Item.notes.property.collection_class([note, ])  # OK

But I can use other Classes, for example (http://docs.sqlalchemy.org/en/rel_0_9/orm/collections.html#dictionary-collections):

from sqlalchemy import Column, Integer, String, ForeignKey
from sqlalchemy.orm import relationship
from sqlalchemy.orm.collections import attribute_mapped_collection
from sqlalchemy.ext.declarative import declarative_base

Base = declarative_base()


class Item(Base):
    __tablename__ = 'item'
    id = Column(Integer, primary_key=True)
    notes = relationship("Note",
                collection_class=attribute_mapped_collection('keyword'),
                cascade="all, delete-orphan")


class Note(Base):
    __tablename__ = 'note'
    id = Column(Integer, primary_key=True)
    item_id = Column(Integer, ForeignKey('item.id'), nullable=False)
    keyword = Column(String)
    text = Column(String)

    def __init__(self, keyword, text):
        self.keyword = keyword
        self.text = text

item = Item()
note = Note("foo", "bar")
Item.notes.property.collection_class([note, ])

And it raises error:

Traceback (most recent call last):
  File "foofoo.py", line 30, in <module>
    Item.notes.property.collection_class([note, ])
TypeError: <lambda>() takes 0 positional arguments but 1 was given

This is most likely a bug in sacrud, but I don't know how it to best solve at the moment