fix: disuse __slots__ in most places (#330)

In Python 2.7, classes which use `__slots__` can't be pickled. Users
have reported problems trying to pickle NDB entities, indicating there
is some perceived use case for pickling entities.

Fixes #311

google/cloud/ndb/_datastore_types.py

@@ -51,8 +51,6 @@ class BlobKey(object):
             :class:`bytes` instance.
     """
 
-    __slots__ = ("_blob_key",)
-
     def __init__(self, blob_key):
         if isinstance(blob_key, bytes):
             if len(blob_key) > _MAX_STRING_LENGTH:

google/cloud/ndb/_eventloop.py

@@ -135,15 +135,6 @@ class EventLoop(object):
             get added to this queue and then processed by the event loop.
     """
 
-    __slots__ = (
-        "current",
-        "idlers",
-        "inactive",
-        "queue",
-        "rpcs",
-        "rpc_results",
-    )
-
     def __init__(self):
         self.current = collections.deque()
         self.idlers = collections.deque()

google/cloud/ndb/blobstore.py

@@ -78,8 +78,6 @@ def __init__(self, *args, **kwargs):
 
 
 class BlobInfo(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()
 
@@ -111,8 +109,6 @@ def __init__(self, *args, **kwargs):
 
 
 class BlobReader(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()
 

google/cloud/ndb/context.py

@@ -546,21 +546,15 @@ def urlfetch(self, *args, **kwargs):
 
 
 class ContextOptions(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()
 
 
 class TransactionOptions(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()
 
 
 class AutoBatcher(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()

google/cloud/ndb/django_middleware.py

@@ -19,7 +19,5 @@
 
 
 class NdbDjangoMiddleware(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise NotImplementedError

google/cloud/ndb/key.py

@@ -272,8 +272,6 @@ class Key(object):
             arguments were given with the path.
     """
 
-    __slots__ = ("_key", "_reference")
-
     def __new__(cls, *path_args, **kwargs):
         # Avoid circular import in Python 2.7
         from google.cloud.ndb import context as context_module

google/cloud/ndb/metadata.py

@@ -59,8 +59,6 @@
 class _BaseMetadata(model.Model):
     """Base class for all metadata models."""
 
-    __slots__ = ()
-
     _use_cache = False
     _use_global_cache = False
 
@@ -81,8 +79,6 @@ def _get_kind(cls):
 class Namespace(_BaseMetadata):
     """Model for __namespace__ metadata query results."""
 
-    __slots__ = ()
-
     KIND_NAME = "__namespace__"
     EMPTY_NAMESPACE_ID = 1
 
@@ -127,8 +123,6 @@ def key_to_namespace(cls, key):
 class Kind(_BaseMetadata):
     """Model for __kind__ metadata query results."""
 
-    __slots__ = ()
-
     KIND_NAME = "__kind__"
 
     @property
@@ -168,8 +162,6 @@ def key_to_kind(cls, key):
 class Property(_BaseMetadata):
     """Model for __property__ metadata query results."""
 
-    __slots__ = ()
-
     KIND_NAME = "__property__"
 
     @property

google/cloud/ndb/model.py

@@ -388,8 +388,6 @@ def __ne__(self, other):
 class IndexProperty(_NotEqualMixin):
     """Immutable object representing a single property in an index."""
 
-    __slots__ = ("_name", "_direction")
-
     @utils.positional(1)
     def __new__(cls, name, direction):
         instance = super(IndexProperty, cls).__new__(cls)
@@ -426,8 +424,6 @@ def __hash__(self):
 class Index(_NotEqualMixin):
     """Immutable object representing an index."""
 
-    __slots__ = ("_kind", "_properties", "_ancestor")
-
     @utils.positional(1)
     def __new__(cls, kind, properties, ancestor):
         instance = super(Index, cls).__new__(cls)
@@ -475,8 +471,6 @@ def __hash__(self):
 class IndexState(_NotEqualMixin):
     """Immutable object representing an index and its state."""
 
-    __slots__ = ("_definition", "_state", "_id")
-
     @utils.positional(1)
     def __new__(cls, definition, state, id):
         instance = super(IndexState, cls).__new__(cls)
@@ -526,8 +520,6 @@ def __hash__(self):
 
 
 class ModelAdapter(object):
-    __slots__ = ()
-
     def __new__(self, *args, **kwargs):
         raise exceptions.NoLongerImplementedError()
 
@@ -796,8 +788,6 @@ def make_connection(*args, **kwargs):
 class ModelAttribute(object):
     """Base for classes that implement a ``_fix_up()`` method."""
 
-    __slots__ = ()
-
     def _fix_up(self, cls, code_name):
         """Fix-up property name. To be implemented by subclasses.
 
@@ -824,8 +814,6 @@ class _BaseValue(_NotEqualMixin):
         TypeError: If ``b_val`` is a list.
     """
 
-    __slots__ = ("b_val",)
-
     def __init__(self, b_val):
         if b_val is None:
             raise TypeError("Cannot wrap None")
@@ -2169,8 +2157,6 @@ class ModelKey(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def __init__(self):
         super(ModelKey, self).__init__()
         self._name = "__key__"
@@ -2253,8 +2239,6 @@ class BooleanProperty(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -2285,8 +2269,6 @@ class IntegerProperty(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -2318,8 +2300,6 @@ class FloatProperty(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -2602,8 +2582,6 @@ class Item(ndb.Model):
         NotImplementedError: If ``indexed=True`` is provided.
     """
 
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         indexed = kwargs.pop("indexed", False)
         if indexed:
@@ -2732,8 +2710,6 @@ class StringProperty(TextProperty):
         NotImplementedError: If ``indexed=False`` is provided.
     """
 
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         indexed = kwargs.pop("indexed", True)
         if not indexed:
@@ -2757,8 +2733,6 @@ class GeoPtProperty(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -2967,8 +2941,6 @@ class User(object):
         UserNotFoundError: If ``email`` is empty.
     """
 
-    __slots__ = ("_auth_domain", "_email", "_user_id")
-
     def __init__(self, email=None, _auth_domain=None, _user_id=None):
         if _auth_domain is None:
             raise ValueError("_auth_domain is required")
@@ -3465,8 +3437,6 @@ class BlobKeyProperty(Property):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -3685,8 +3655,6 @@ class DateProperty(DateTimeProperty):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 
@@ -3747,8 +3715,6 @@ class TimeProperty(DateTimeProperty):
     .. automethod:: _validate
     """
 
-    __slots__ = ()
-
     def _validate(self, value):
         """Validate a ``value`` before setting it.
 

google/cloud/ndb/msgprop.py

@@ -19,14 +19,10 @@
 
 
 class EnumProperty(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise NotImplementedError
 
 
 class MessageProperty(object):
-    __slots__ = ()
-
     def __init__(self, *args, **kwargs):
         raise NotImplementedError

google/cloud/ndb/query.py

@@ -183,8 +183,6 @@ class PropertyOrder(object):
                or not (ascending). Default is False.
     """
 
-    __slots__ = ["name", "reverse"]
-
     def __init__(self, name, reverse=False):
         self.name = name
         self.reverse = reverse
@@ -227,8 +225,6 @@ class RepeatedStructuredPropertyPredicate(object):
             contain a value for each key in ``match_keys``.
     """
 
-    __slots__ = ["name", "match_keys", "match_values"]
-
     def __init__(self, name, match_keys, entity_pb):
         self.name = name
         self.match_keys = match_keys
@@ -305,8 +301,6 @@ class Parameter(ParameterizedThing):
         TypeError: If the ``key`` is not a string or integer.
     """
 
-    __slots__ = ("_key",)
-
     def __init__(self, key):
         if not isinstance(key, six.integer_types + six.string_types):
             raise TypeError(
@@ -411,8 +405,6 @@ class Node(object):
 
     _multiquery = False
 
-    __slots__ = ()
-
     def __new__(cls):
         if cls is Node:
             raise TypeError("Cannot instantiate Node, only a subclass.")
@@ -479,8 +471,6 @@ def resolve(self, bindings, used):
 class FalseNode(Node):
     """Tree node for an always-failing filter."""
 
-    __slots__ = ()
-
     def __eq__(self, other):
         """Equality check.
 
@@ -524,8 +514,6 @@ class ParameterNode(Node):
             :class:`.ParameterizedFunction`.
     """
 
-    __slots__ = ("_prop", "_op", "_param")
-
     def __new__(cls, prop, op, param):
         # Avoid circular import in Python 2.7
         from google.cloud.ndb import model
@@ -643,7 +631,9 @@ class FilterNode(Node):
             :class:`frozenset`)
     """
 
-    __slots__ = ("_name", "_opsymbol", "_value")
+    _name = None
+    _opsymbol = None
+    _value = None
 
     def __new__(cls, name, opsymbol, value):
         # Avoid circular import in Python 2.7
@@ -754,8 +744,6 @@ class PostFilterNode(Node):
             the given filter.
     """
 
-    __slots__ = ("predicate",)
-
     def __new__(cls, predicate):
         instance = super(PostFilterNode, cls).__new__(cls)
         instance.predicate = predicate
@@ -826,8 +814,6 @@ class _BooleanClauses(object):
             with the current boolean expression via ``AND`` or ``OR``.
     """
 
-    __slots__ = ("name", "combine_or", "or_parts")
-
     def __init__(self, name, combine_or):
         self.name = name
         self.combine_or = combine_or
@@ -919,8 +905,6 @@ class ConjunctionNode(Node):
             expression.
     """
 
-    __slots__ = ("_nodes",)
-
     def __new__(cls, *nodes):
         if not nodes:
             raise TypeError("ConjunctionNode() requires at least one node.")
@@ -1075,7 +1059,6 @@ class DisjunctionNode(Node):
     """
 
     _multiquery = True
-    __slots__ = ("_nodes",)
 
     def __new__(cls, *nodes):
         if not nodes: