[BEAM-8280] Enable type hint annotations

CHANGES.md

@@ -54,6 +54,19 @@
 ## I/Os
 
 ## New Features / Improvements
+* Python SDK will now use Python 3 type annotations as pipeline type hints.
+([#10717](https://github.com/apache/beam/pull/10717))
+
+    If you suspect that this feature is causing your pipeline to fail, calling
+    `apache_beam.typehints.disable_type_annotations()` before pipeline creation
+    will disable is completely, and decorating specific functions (such as 
+    `process()`) with `@apache_beam.typehints.no_annotations` will disable it
+    for that function.
+
+    More details will be in 
+    [Ensuring Python Type Safety](https://beam.apache.org/documentation/sdks/python-type-safety/)
+    and an upcoming
+    [blog post](https://beam.apache.org/blog/python/typing/2020/03/06/python-typing.html).
 
 ## Breaking Changes
 

sdks/python/apache_beam/typehints/decorators.py

@@ -120,6 +120,7 @@ def foo((a, b)):
   funcsigs = None
 
 __all__ = [
+    'disable_type_annotations',
     'no_annotations',
     'with_input_types',
     'with_output_types',
@@ -138,8 +139,7 @@ def foo((a, b)):
 
 _ANY_VAR_POSITIONAL = typehints.Tuple[typehints.Any, ...]
 _ANY_VAR_KEYWORD = typehints.Dict[typehints.Any, typehints.Any]
-# TODO(BEAM-8280): Remove this when from_callable is ready to be enabled.
-_enable_from_callable = False
+_disable_from_callable = False
 
 try:
   _original_getfullargspec = inspect.getfullargspec
@@ -231,6 +231,16 @@ def no_annotations(fn):
   return fn
 
 
+def disable_type_annotations():
+  """Prevent Beam from using type hint annotations to determine input and output
+  types of transforms.
+
+  This setting applies globally.
+  """
+  global _disable_from_callable
+  _disable_from_callable = True
+
+
 class IOTypeHints(NamedTuple(
     'IOTypeHints',
     [('input_types', Optional[Tuple[Tuple[Any, ...], Dict[str, Any]]]),
@@ -298,7 +308,7 @@ def from_callable(cls, fn):
     Returns:
       A new IOTypeHints or None if no annotations found.
     """
-    if not _enable_from_callable or getattr(fn, '_beam_no_annotations', False):
+    if _disable_from_callable or getattr(fn, '_beam_no_annotations', False):
       return None
     signature = get_signature(fn)
     if (all(param.annotation == param.empty

sdks/python/apache_beam/typehints/decorators_test.py

@@ -33,8 +33,6 @@
 from apache_beam.typehints import decorators
 from apache_beam.typehints import typehints
 
-decorators._enable_from_callable = True
-
 
 class IOTypeHintsTest(unittest.TestCase):
   def test_get_signature(self):
@@ -221,5 +219,15 @@ def __init__(self):
         Subclass().with_input_types(str)._type_hints, Subclass._type_hints)
 
 
+class DecoratorsTest(unittest.TestCase):
+  def tearDown(self):
+    decorators._disable_from_callable = False
+
+  def test_disable_type_annotations(self):
+    self.assertFalse(decorators._disable_from_callable)
+    decorators.disable_type_annotations()
+    self.assertTrue(decorators._disable_from_callable)
+
+
 if __name__ == '__main__':
   unittest.main()

sdks/python/apache_beam/typehints/decorators_test_py3.py

@@ -37,7 +37,6 @@
 from apache_beam.typehints import TypeVariable
 from apache_beam.typehints import decorators
 
-decorators._enable_from_callable = True
 T = TypeVariable('T')
 # Name is 'T' so it converts to a beam type with the same name.
 # mypy requires that the name of the variable match, so we must ignore this.
@@ -194,5 +193,23 @@ def fn(a: int) -> int:
     _ = ['a', 'b', 'c'] | Map(fn)
 
 
+class DecoratorsTest(unittest.TestCase):
+  def test_no_annotations(self):
+    def fn(a: int) -> int:
+      return a
+
+    _ = [1, 2, 3] | Map(fn)  # Doesn't raise - correct types.
+
+    with self.assertRaisesRegex(TypeCheckError,
+                                r'requires .*int.* but got .*str'):
+      _ = ['a', 'b', 'c'] | Map(fn)
+
+    @decorators.no_annotations
+    def fn2(a: int) -> int:
+      return a
+
+    _ = ['a', 'b', 'c'] | Map(fn2)  # Doesn't raise - no input type hints.
+
+
 if __name__ == '__main__':
   unittest.main()

sdks/python/apache_beam/typehints/typed_pipeline_test.py

@@ -36,15 +36,12 @@
 from apache_beam.testing.util import assert_that
 from apache_beam.testing.util import equal_to
 from apache_beam.typehints import WithTypeHints
-from apache_beam.typehints import decorators
 from apache_beam.typehints.decorators import get_signature
 
 # These test often construct a pipeline as value | PTransform to test side
 # effects (e.g. errors).
 # pylint: disable=expression-not-assigned
 
-decorators._enable_from_callable = True
-
 
 class MainInputTest(unittest.TestCase):
   def test_bad_main_input(self):

sdks/python/apache_beam/typehints/typed_pipeline_test_py3.py

@@ -26,9 +26,6 @@
 
 import apache_beam as beam
 from apache_beam import typehints
-from apache_beam.typehints import decorators
-
-decorators._enable_from_callable = True
 
 
 class MainInputTest(unittest.TestCase):

sdks/python/apache_beam/typehints/typehints_test_py3.py

@@ -28,9 +28,6 @@
 from apache_beam.transforms.core import DoFn
 from apache_beam.typehints import KV
 from apache_beam.typehints import Iterable
-from apache_beam.typehints import decorators
-
-decorators._enable_from_callable = True
 
 
 class TestParDoAnnotations(unittest.TestCase):