Test and fix attrs type inference when using the typing module (#2092)

Test and fix attrs type inference when using the typing module

CONTRIBUTING.rst

@@ -227,6 +227,7 @@ their individual contributions.
 * `JP Viljoen <https://github.com/froztbyte>`_ (froztbyte@froztbyte.net)
 * `Jochen Müller <https://github.com/jomuel>`_
 * `Joey Tuong <https://github.com/tetrapus>`_
+* `Jonathan Gayvallet <https://github.com/Meallia>`_ (jonathan.gayvallet@orange.com)
 * `Jonty Wareing <https://www.github.com/Jonty>`_ (jonty@jonty.co.uk)
 * `Joshua Boone <https://www.github.com/patchedwork>`_ (joshuaboone4190@gmail.com)
 * `jmhsi <https://www.github.com/jmhsi>`_

hypothesis-python/RELEASE.rst

@@ -0,0 +1,7 @@
+RELEASE_TYPE: patch
+
+This patch fixes a bug in strategy inference for :pypi:`attrs` classes where
+Hypothesis would fail to infer a strategy for attributes of a generic type
+such as ``Union[int, str]`` or ``List[bool]`` (:issue:`2091`).
+
+Thanks to Jonathan Gayvallet for the bug report and this patch!

hypothesis-python/src/hypothesis/core.py

@@ -508,14 +508,7 @@ def __init__(self, test_runner, search_strategy, test, settings, random, had_see
 
         self.used_examples_from_database = False
 
-    def execute(
-        self,
-        data,
-        print_example=False,
-        is_final=False,
-        expected_failure=None,
-        collect=False,
-    ):
+    def execute(self, data, print_example=False, is_final=False, expected_failure=None):
         text_repr = [None]
         if self.settings.deadline is None:
             test = self.test

hypothesis-python/src/hypothesis/internal/compat.py

@@ -304,7 +304,11 @@ def qualname(f):
         typing_root_type = (typing._Final, typing._GenericAlias)  # type: ignore
         ForwardRef = typing.ForwardRef  # type: ignore
     except AttributeError:
-        typing_root_type = (typing.TypingMeta, typing.TypeVar)  # type: ignore
+        typing_root_type = (
+            typing.TypingMeta,
+            typing.TypeVar,
+            typing._Union,
+        )  # type: ignore
         ForwardRef = typing._ForwardRef  # type: ignore
 
 

hypothesis-python/src/hypothesis/searchstrategy/attrs.py

@@ -25,7 +25,7 @@
 import hypothesis.strategies as st
 from hypothesis.errors import ResolutionFailed
 from hypothesis.internal.compat import get_type_hints, string_types
-from hypothesis.searchstrategy.types import type_sorting_key
+from hypothesis.searchstrategy.types import is_a_type, type_sorting_key
 from hypothesis.utils.conventions import infer
 
 
@@ -124,7 +124,7 @@ def types_to_strategy(attrib, types):
 
     # Otherwise, try the `type` attribute as a fallback, and finally try
     # the type hints on a converter (desperate!) before giving up.
-    if isinstance(getattr(attrib, "type", None), type):
+    if is_a_type(getattr(attrib, "type", None)):
         # The convoluted test is because variable annotations may be stored
         # in string form; attrs doesn't evaluate them and we don't handle them.
         # See PEP 526, PEP 563, and Hypothesis issue #1004 for details.

hypothesis-python/tests/cover/test_attrs_inference.py

@@ -24,6 +24,11 @@
 from hypothesis import given, infer
 from hypothesis.errors import ResolutionFailed
 
+try:
+    import typing
+except ImportError:
+    typing = None
+
 
 @attr.s
 class Inferrables(object):
@@ -54,6 +59,14 @@ class Inferrables(object):
     validator_in_multiple_strings = attr.ib(
         validator=[attr.validators.in_("abcd"), attr.validators.in_(["ab", "cd"])]
     )
+
+    if typing is not None:
+        typing_list = attr.ib(type=typing.List[int])
+        typing_list_of_list = attr.ib(type=typing.List[typing.List[int]])
+        typing_dict = attr.ib(type=typing.Dict[str, int])
+        typing_union = attr.ib(type=typing.Optional[bool])
+        typing_union = attr.ib(type=typing.Union[str, int])
+
     has_default = attr.ib(default=0)
     has_default_factory = attr.ib(default=attr.Factory(list))
     has_default_factory_takes_self = attr.ib(  # uninferrable but has default