Apiobject subclass mapping

CHANGELOG.md

@@ -1,3 +1,9 @@
+## Betsy Ross (Unreleased)
+
+### Changes
+
+ - Use Mapping instead of dict as the base class for APIObject ([#756](https:/fishtown-analytics/dbt/pull/756))
+
 ## dbt 0.10.1 (Unreleased)
 
 This release focuses on achieving functional parity between all of dbt's adapters. With this release, most dbt functionality should work on every adapter except where noted [here](https://docs.getdbt.com/v0.10/docs/supported-databases#section-caveats).

dbt/api/object.py

@@ -1,11 +1,12 @@
 import copy
+from collections import Mapping
 from jsonschema import Draft4Validator
 
 from dbt.exceptions import ValidationException
 from dbt.utils import deep_merge
 
 
-class APIObject(dict):
+class APIObject(Mapping):
  """
  A serializable / deserializable object intended for
  use in a future dbt API.
@@ -24,17 +25,15 @@ class APIObject(dict):
 
  DEFAULTS = {}
 
- def __init__(self, *args, **kwargs):
+ def __init__(self, **kwargs):
  """
- Create and validate an instance. Note that it's
- not a good idea to override this.
+ Create and validate an instance. Note that if you override this, you
+ will want to do so by modifying kwargs and only then calling
+ super(NewClass, self).__init__(**kwargs).
  """
- defaults = copy.deepcopy(self.DEFAULTS)
- settings = copy.deepcopy(kwargs)
-
- d = deep_merge(defaults, settings)
- super(APIObject, self).__init__(*args, **d)
- self.__dict__ = self
+ super(APIObject, self).__init__()
+ # note: deep_merge does a deep copy on its arguments.
+ self._contents = deep_merge(self.DEFAULTS, kwargs)
  self.validate()
 
  def incorporate(self, **kwargs):
@@ -43,15 +42,13 @@ def incorporate(self, **kwargs):
  into a new copy of this instance, and return the new
  instance after validating.
  """
- existing = copy.deepcopy(dict(self))
- updates = copy.deepcopy(kwargs)
- return type(self)(**deep_merge(existing, updates))
+ return type(self)(**deep_merge(self._contents, kwargs))
 
  def serialize(self):
  """
  Return a dict representation of this object.
  """
- return dict(self)
+ return copy.deepcopy(self._contents)
 
  @classmethod
  def deserialize(cls, settings):
@@ -72,11 +69,37 @@ def validate(self):
  errors = []
 
  for error in validator.iter_errors(self.serialize()):
- errors.append('property "{}", {}'.format(
- ".".join(error.path), error.message))
+ errors.append('.'.join(
+ list(map(str, error.path)) + [error.message])
+ )
 
  if errors:
  raise ValidationException(
  'Invalid arguments passed to "{}" instance: {}'
  .format(type(self).__name__,
  ", ".join(errors)))
+
+ # implement the Mapping protocol:
+ # https://docs.python.org/3/library/collections.abc.html
+ def __getitem__(self, key):
+ return self._contents[key]
+
+ def __iter__(self):
+ return self._contents.__iter__()
+
+ def __len__(self):
+ return self._contents.__len__()
+
+ # implement this because everyone always expects it.
+ def get(self, key, default=None):
+ return self._contents.get(key, default)
+
+ # most users of APIObject also expect the attributes to be available via
+ # dot-notation because the previous implementation assigned to __dict__.
+ # we should consider removing this if we fix all uses to have properties.
+ def __getattr__(self, name):
+ if name in self._contents:
+ return self._contents[name]
+ raise AttributeError((
+ "'{}' object has no attribute '{}'"
+ ).format(type(self).__name__, name))

dbt/utils.py

@@ -2,6 +2,7 @@
 import hashlib
 import itertools
 import collections
+import copy
 import functools
 
 import dbt.exceptions
@@ -240,10 +241,10 @@ def deep_merge(*args):
  return None
 
  if len(args) == 1:
- return args[0]
+ return copy.deepcopy(args[0])
 
  lst = list(args)
- last = lst.pop(len(lst)-1)
+ last = copy.deepcopy(lst.pop(len(lst)-1))
 
  return _deep_merge(deep_merge(*lst), last)