#
# Licensed to the Apache Software Foundation (ASF) under one or more
# contributor license agreements. See the NOTICE file distributed with
# this work for additional information regarding copyright ownership.
# The ASF licenses this file to You under the Apache License, Version 2.0
# (the "License"); you may not use this file except in compliance with
# the License. You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an "AS IS" BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
#
"""Runtime type checking support.
For internal use only; no backwards-compatibility guarantees.
"""
import collections
import inspect
import sys
import types
from apache_beam.pvalue import TaggedOutput
from apache_beam.transforms.core import DoFn
from apache_beam.transforms.window import WindowedValue
from apache_beam.typehints.decorators import _check_instance_type
from apache_beam.typehints.decorators import getcallargs_forhints
from apache_beam.typehints.decorators import GeneratorWrapper
from apache_beam.typehints.decorators import TypeCheckError
from apache_beam.typehints.typehints import check_constraint
from apache_beam.typehints.typehints import CompositeTypeHintError
from apache_beam.typehints.typehints import SimpleTypeHintError
[docs]class AbstractDoFnWrapper(DoFn):
"""An abstract class to create wrapper around DoFn"""
def __init__(self, dofn):
super(AbstractDoFnWrapper, self).__init__()
self.dofn = dofn
def _inspect_start_bundle(self):
return self.dofn.get_function_arguments('start_bundle')
def _inspect_process(self):
return self.dofn.get_function_arguments('process')
def _inspect_finish_bundle(self):
return self.dofn.get_function_arguments('finish_bundle')
[docs] def wrapper(self, method, args, kwargs):
return method(*args, **kwargs)
[docs] def start_bundle(self, *args, **kwargs):
return self.wrapper(self.dofn.start_bundle, args, kwargs)
[docs] def process(self, *args, **kwargs):
return self.wrapper(self.dofn.process, args, kwargs)
[docs] def finish_bundle(self, *args, **kwargs):
return self.wrapper(self.dofn.finish_bundle, args, kwargs)
[docs] def is_process_bounded(self):
return self.dofn.is_process_bounded()
[docs]class OutputCheckWrapperDoFn(AbstractDoFnWrapper):
"""A DoFn that verifies against common errors in the output type."""
def __init__(self, dofn, full_label):
super(OutputCheckWrapperDoFn, self).__init__(dofn)
self.full_label = full_label
[docs] def wrapper(self, method, args, kwargs):
try:
result = method(*args, **kwargs)
except TypeCheckError as e:
error_msg = ('Runtime type violation detected within ParDo(%s): '
'%s' % (self.full_label, e))
raise TypeCheckError, error_msg, sys.exc_info()[2]
else:
return self._check_type(result)
def _check_type(self, output):
if output is None:
return output
elif isinstance(output, (dict, basestring)):
object_type = type(output).__name__
raise TypeCheckError('Returning a %s from a ParDo or FlatMap is '
'discouraged. Please use list("%s") if you really '
'want this behavior.' %
(object_type, output))
elif not isinstance(output, collections.Iterable):
raise TypeCheckError('FlatMap and ParDo must return an '
'iterable. %s was returned instead.'
% type(output))
return output
[docs]class TypeCheckWrapperDoFn(AbstractDoFnWrapper):
"""A wrapper around a DoFn which performs type-checking of input and output.
"""
def __init__(self, dofn, type_hints, label=None):
super(TypeCheckWrapperDoFn, self).__init__(dofn)
self.dofn = dofn
self._process_fn = self.dofn._process_argspec_fn()
if type_hints.input_types:
input_args, input_kwargs = type_hints.input_types
self._input_hints = getcallargs_forhints(
self._process_fn, *input_args, **input_kwargs)
else:
self._input_hints = None
# TODO(robertwb): Multi-output.
self._output_type_hint = type_hints.simple_output_type(label)
[docs] def wrapper(self, method, args, kwargs):
result = method(*args, **kwargs)
return self._type_check_result(result)
[docs] def process(self, *args, **kwargs):
if self._input_hints:
actual_inputs = inspect.getcallargs(self._process_fn, *args, **kwargs)
for var, hint in self._input_hints.items():
if hint is actual_inputs[var]:
# self parameter
continue
_check_instance_type(hint, actual_inputs[var], var, True)
return self._type_check_result(self.dofn.process(*args, **kwargs))
def _type_check_result(self, transform_results):
if self._output_type_hint is None or transform_results is None:
return transform_results
def type_check_output(o):
# TODO(robertwb): Multi-output.
x = o.value if isinstance(o, (TaggedOutput, WindowedValue)) else o
self._type_check(self._output_type_hint, x, is_input=False)
# If the return type is a generator, then we will need to interleave our
# type-checking with its normal iteration so we don't deplete the
# generator initially just by type-checking its yielded contents.
if isinstance(transform_results, types.GeneratorType):
return GeneratorWrapper(transform_results, type_check_output)
for o in transform_results:
type_check_output(o)
return transform_results
def _type_check(self, type_constraint, datum, is_input):
"""Typecheck a PTransform related datum according to a type constraint.
This function is used to optionally type-check either an input or an output
to a PTransform.
Args:
type_constraint: An instance of a typehints.TypeContraint, one of the
white-listed builtin Python types, or a custom user class.
datum: An instance of a Python object.
is_input: True if 'datum' is an input to a PTransform's DoFn. False
otherwise.
Raises:
TypeError: If 'datum' fails to type-check according to 'type_constraint'.
"""
datum_type = 'input' if is_input else 'output'
try:
check_constraint(type_constraint, datum)
except CompositeTypeHintError as e:
raise TypeCheckError, e.message, sys.exc_info()[2]
except SimpleTypeHintError:
error_msg = ("According to type-hint expected %s should be of type %s. "
"Instead, received '%s', an instance of type %s."
% (datum_type, type_constraint, datum, type(datum)))
raise TypeCheckError, error_msg, sys.exc_info()[2]