Fix required arg handling under Python2

src/hypothesis/searchstrategy/types.py

@@ -35,7 +35,8 @@
 def required_args(target, args=(), kwargs=()):
  """Return a set of required args to target."""
  try:
- spec = getfullargspec(target)
+ spec = getfullargspec(
+ target.__init__ if inspect.isclass(target) else target)
  except TypeError:
  return None
  # For classes, self is present in the argspec but not really required

src/hypothesis/strategies.py

@@ -910,20 +910,18 @@ def from_type(thing):
  elif strategies:
  return one_of(strategies)
  # If we don't have a strategy registered for this type or any subtype, we
- # may be able to fall back on type annotations. If the constructor has
- # an annotation for every required argument, we can (and do) use builds().
- required = types.required_args(thing)
- if not required or required.issubset(get_type_hints(thing.__init__)):
- return builds(thing)
- # The final special case is types created via typing.NamedTuple, which
- # use a custom attribute but not annotations for their types. We can use
- # builds() for this again, if we work out the right kwargs.
+ # may be able to fall back on type annotations.
+ # Types created via typing.NamedTuple use a custom attribute instead -
+ # but we can still use builds(), if we work out the right kwargs.
  if issubclass(thing, tuple) and hasattr(thing, '_fields') \
  and hasattr(thing, '_field_types'):
- # Special handling for user-defined typing.NamedTuple
- # collections.namedtuples can't be inferred; add then to lookup
  kwargs = {k: from_type(thing._field_types[k]) for k in thing._fields}
  return builds(thing, **kwargs)
+ # If the constructor has an annotation for every required argument,
+ # we can (and do) use builds() without supplying additional arguments.
+ required = types.required_args(thing)
+ if not required or required.issubset(get_type_hints(thing.__init__)):
+ return builds(thing)
  # We have utterly failed, and might as well say so now.
  raise ResolutionFailed('Could not resolve %r to a strategy; consider '
  'using register_type_strategy' % (thing,))