First pass at Python2.7 compatibility

.coveragerc

@@ -7,6 +7,7 @@ show_missing = True
 exclude_lines =
     # Re-enable the standard pragma
     pragma: NO COVER
+    pragma: NO PY${PY_VERSION} COVER
 omit =
   */gapic/*.py
   */proto/*.py

google/cloud/ndb/_batch.py

@@ -14,7 +14,6 @@
 
 """Support for batching operations."""
 
-from google.cloud.ndb import context as context_module
 from google.cloud.ndb import _eventloop
 
 
@@ -35,6 +34,9 @@ def get_batch(batch_cls, options=None):
     Returns:
         batch_cls: An instance of the batch class.
     """
+    # prevent circular import in Python 2.7
+    from google.cloud.ndb import context as context_module
+
     context = context_module.get_context()
     batches = context.batches.get(batch_cls)
     if batches is None:

google/cloud/ndb/_cache.py

@@ -12,19 +12,25 @@
 # See the License for the specific language governing permissions and
 # limitations under the License.
 
-import collections
 import itertools
 
 from google.cloud.ndb import _batch
 from google.cloud.ndb import context as context_module
 from google.cloud.ndb import tasklets
 
+# For Python 2.7 Compatibility
+try:
+    from collections import UserDict
+except ImportError:  # pragma: NO PY3 COVER
+    from UserDict import UserDict
+
+
 _LOCKED = b"0"
 _LOCK_TIME = 32
 _PREFIX = b"NDB30"
 
 
-class ContextCache(collections.UserDict):
+class ContextCache(UserDict):
     """A per-context in-memory entity cache.
 
     This cache verifies the fetched entity has the correct key before
@@ -55,7 +61,7 @@ def _future_result(result):
     return future
 
 
-class _GlobalCacheBatch:
+class _GlobalCacheBatch(object):
     """Abstract base for classes used to batch operations for the global cache.
     """
 

google/cloud/ndb/_datastore_api.py

@@ -179,7 +179,7 @@ def lookup(key, options):
     raise tasklets.Return(entity_pb)
 
 
-class _LookupBatch:
+class _LookupBatch(object):
     """Batch for Lookup requests.
 
     Attributes:
@@ -456,7 +456,7 @@ def delete(key, options):
         yield _cache.global_delete(cache_key)
 
 
-class _NonTransactionalCommitBatch:
+class _NonTransactionalCommitBatch(object):
     """Batch for tracking a set of mutations for a non-transactional commit.
 
     Attributes:
@@ -858,7 +858,7 @@ def allocate(keys, options):
     return batch.add(keys)
 
 
-class _AllocateIdsBatch:
+class _AllocateIdsBatch(object):
     """Batch for AllocateIds requests.
 
     Not related to batch used by transactions to allocate ids for upserts

google/cloud/ndb/_datastore_query.py

@@ -1,3 +1,4 @@
+# -*- coding: utf-8 -*-
 # Copyright 2018 Google LLC
 #
 # Licensed under the Apache License, Version 2.0 (the "License");
@@ -129,7 +130,7 @@ def iterate(query, raw=False):
     return _QueryIteratorImpl(query, raw=raw)
 
 
-class QueryIterator:
+class QueryIterator(object):
     """An iterator for query results.
 
     Executes the given query and provides an interface for iterating over
@@ -502,7 +503,7 @@ def __init__(self, query, raw=False):
             query.copy(filters=node, offset=None, limit=None)
             for node in query.filters._nodes
         ]
-        self._result_sets = [iterate(query, raw=True) for query in queries]
+        self._result_sets = [iterate(_query, raw=True) for _query in queries]
         self._sortable = bool(query.order_by)
         self._seen_keys = set()
         self._next_result = None
@@ -616,7 +617,7 @@ def cursor_after(self):
 
 
 @functools.total_ordering
-class _Result:
+class _Result(object):
     """A single, sortable query result.
 
     Args:
@@ -645,6 +646,10 @@ def __eq__(self, other):
 
         return self._compare(other) == 0
 
+    def __ne__(self, other):
+        """For total ordering. Python 2.7 only."""
+        return self._compare(other) != 0
+
     def _compare(self, other):
         """Compare this result to another result for sorting.
 
@@ -847,7 +852,7 @@ def _datastore_run_query(query):
     raise tasklets.Return(response)
 
 
-class Cursor:
+class Cursor(object):
     """Cursor.
 
     A pointer to a place in a sequence of query results. Cursor itself is just

google/cloud/ndb/_datastore_types.py

@@ -29,7 +29,7 @@
 
 
 @functools.total_ordering
-class BlobKey:
+class BlobKey(object):
     """Key used to identify a blob in the blobstore.
 
     .. note::
@@ -78,11 +78,14 @@ def __eq__(self, other):
 
     def __lt__(self, other):
         if isinstance(other, BlobKey):
+            # Python 2.7 does not raise an error when other is None.
+            if other._blob_key is None:
+                raise TypeError
             return self._blob_key < other._blob_key
         elif isinstance(other, bytes):
             return self._blob_key < other
         else:
-            return NotImplemented
+            raise TypeError
 
     def __hash__(self):
         return hash(self._blob_key)

google/cloud/ndb/_eventloop.py

@@ -17,11 +17,14 @@
 This should handle both asynchronous ``ndb`` objects and arbitrary callbacks.
 """
 import collections
-import queue
 import uuid
 import time
 
-from google.cloud.ndb import context as context_module
+# Python 2.7 module name change
+try:
+    import queue
+except ImportError:  # pragma: NO PY3 COVER
+    import Queue as queue
 
 __all__ = [
     "add_idle",
@@ -47,7 +50,7 @@ def _logging_debug(*args, **kw):
 )
 
 
-class EventLoop:
+class EventLoop(object):
     """An event loop.
 
     Instances of ``EventLoop`` are used to coordinate single threaded execution
@@ -365,6 +368,9 @@ def get_event_loop():
     Returns:
         EventLoop: The event loop for the current context.
     """
+    # Prevent circular import in Python 2.7
+    from google.cloud.ndb import context as context_module
+
     context = context_module.get_context()
     return context.eventloop
 

google/cloud/ndb/_options.py

@@ -15,7 +15,6 @@
 """Support for options."""
 
 import functools
-import inspect
 import itertools
 import logging
 
@@ -24,7 +23,7 @@
 log = logging.getLogger(__name__)
 
 
-class Options:
+class Options(object):
     __slots__ = (
         # Supported
         "retries",
@@ -37,19 +36,19 @@ class Options:
         "force_writes",
         "max_memcache_items",
         "propagation",
+        "deadline",
+        "use_memcache",
+        "memcache_timeout",
     )
 
     @classmethod
     def options(cls, wrapped):
-        # If there are any positional arguments, get their names
         slots = set(cls.slots())
-        signature = inspect.signature(wrapped)
-        positional = [
-            name
-            for name, parameter in signature.parameters.items()
-            if parameter.kind
-            in (parameter.POSITIONAL_ONLY, parameter.POSITIONAL_OR_KEYWORD)
-        ]
+        # If there are any positional arguments, get their names.
+        # inspect.signature is not available in Python 2.7, so we use the
+        # arguments obtained with inspect.getargspec, which come from the
+        # positional decorator used with all query_options decorated methods.
+        positional = getattr(wrapped, "_positional_names", [])
 
         # We need for any non-option arguments to come before any option
         # arguments
@@ -84,11 +83,10 @@ def wrapper(*args, **kwargs):
 
             # If another function that uses options is delegating to this one,
             # we'll already have options.
-            _options = kwargs.pop("_options", None)
-            if not _options:
-                _options = cls(**kw_options)
+            if "_options" not in kwargs:
+                kwargs["_options"] = cls(**kw_options)
 
-            return wrapped(*pass_args, _options=_options, **kwargs)
+            return wrapped(*pass_args, **kwargs)
 
         return wrapper
 
@@ -97,7 +95,7 @@ def slots(cls):
         return itertools.chain(
             *(
                 ancestor.__slots__
-                for ancestor in cls.mro()
+                for ancestor in cls.__mro__
                 if hasattr(ancestor, "__slots__")
             )
         )
@@ -172,6 +170,13 @@ def __eq__(self, other):
 
         return True
 
+    def __ne__(self, other):
+        # required for Python 2.7 compatibility
+        result = self.__eq__(other)
+        if result is NotImplemented:
+            result = False
+        return not result
+
     def __repr__(self):
         options = ", ".join(
             [
@@ -191,7 +196,7 @@ def items(self):
 
 
 class ReadOptions(Options):
-    __slots__ = ("read_consistency", "transaction")
+    __slots__ = ("read_consistency", "read_policy", "transaction")
 
     def __init__(self, config=None, **kwargs):
         read_policy = kwargs.pop("read_policy", None)

google/cloud/ndb/_remote.py

@@ -21,7 +21,7 @@
 from google.cloud.ndb import exceptions
 
 
-class RemoteCall:
+class RemoteCall(object):
     """Represents a remote call.
 
     This is primarily a wrapper for futures returned by gRPC. This holds some

google/cloud/ndb/_retry.py

@@ -28,6 +28,15 @@
 _DEFAULT_RETRIES = 3
 
 
+def wraps_safely(obj, attr_names=functools.WRAPPER_ASSIGNMENTS):
+    """Python 2.7 functools.wraps has a bug where attributes like ``module``
+    are not copied to the wrappers and thus cause attribute errors. This
+    wrapper prevents that problem."""
+    return functools.wraps(
+        obj, assigned=(name for name in attr_names if hasattr(obj, name))
+    )
+
+
 def retry_async(callback, retries=_DEFAULT_RETRIES):
     """Decorator for retrying functions or tasklets asynchronously.
 
@@ -49,7 +58,7 @@ def retry_async(callback, retries=_DEFAULT_RETRIES):
     """
 
     @tasklets.tasklet
-    @functools.wraps(callback)
+    @wraps_safely(callback)
     def retry_wrapper(*args, **kwargs):
         sleep_generator = core_retry.exponential_sleep_generator(
             _DEFAULT_INITIAL_DELAY,
@@ -66,7 +75,7 @@ def retry_wrapper(*args, **kwargs):
                 # `e` is removed from locals at end of block
                 error = e  # See: https://goo.gl/5J8BMK
                 if not is_transient_error(error):
-                    raise
+                    raise error
             else:
                 raise tasklets.Return(result)
 

google/cloud/ndb/_transaction.py

@@ -14,8 +14,6 @@
 
 import functools
 
-from google.cloud.ndb import context as context_module
-from google.cloud.ndb import _datastore_api
 from google.cloud.ndb import exceptions
 from google.cloud.ndb import _retry
 from google.cloud.ndb import tasklets
@@ -28,6 +26,9 @@ def in_transaction():
         bool: :data:`True` if there is a transaction for the current context,
             otherwise :data:`False`.
     """
+    # Avoid circular import in Python 2.7
+    from google.cloud.ndb import context as context_module
+
     return context_module.get_context().transaction is not None
 
 
@@ -73,6 +74,9 @@ def transaction_async(
 
     This is the asynchronous version of :func:`transaction`.
     """
+    # Avoid circular import in Python 2.7
+    from google.cloud.ndb import context as context_module
+
     if propagation is not None:
         raise exceptions.NoLongerImplementedError()
 
@@ -94,6 +98,9 @@ def transaction_async(
 
 @tasklets.tasklet
 def _transaction_async(context, callback, read_only=False):
+    # Avoid circular import in Python 2.7
+    from google.cloud.ndb import _datastore_api
+
     # Start the transaction
     transaction_id = yield _datastore_api.begin_transaction(
         read_only, retries=0
@@ -114,9 +121,9 @@ def _transaction_async(context, callback, read_only=False):
             yield _datastore_api.commit(transaction_id, retries=0)
 
         # Rollback if there is an error
-        except:  # noqa: E722
+        except Exception as e:  # noqa: E722
             yield _datastore_api.rollback(transaction_id)
-            raise
+            raise e
 
         tx_context._clear_global_cache()
         for callback in on_commit_callbacks: