Support generic types in signature inspection

hypothesis-python/RELEASE.rst

@@ -0,0 +1,8 @@
+RELEASE_TYPE: patch
+
+This patch improves :func:`~hypothesis.strategies.builds` and
+:func:`~hypothesis.strategies.from_type` support for explicitly defined ``__signature__``
+attributes, from :ref:`version 5.8.3 <v5.8.3>`, to support generic types from the
+:mod:`python:typing` module.
+
+Thanks to Rónán Carrigan for identifying and fixing this problem!

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

@@ -130,12 +130,14 @@ def get_type_hints(thing):
             # comprehensive type information from get_type_hints
             # See https://github.com/HypothesisWorks/hypothesis/pull/2580
             # for more details.
+            from hypothesis.strategies._internal.types import is_a_type
+
             spec = inspect.getfullargspec(thing)
             hints.update(
                 {
                     k: v
                     for k, v in spec.annotations.items()
-                    if k in (spec.args + spec.kwonlyargs) and isinstance(v, type)
+                    if k in (spec.args + spec.kwonlyargs) and is_a_type(v)
                 }
             )
     except (AttributeError, TypeError, NameError):

hypothesis-python/tests/nocover/test_build_signature.py

@@ -14,7 +14,7 @@
 # END HEADER
 
 from inspect import signature
-from typing import get_type_hints
+from typing import List, get_type_hints
 
 from hypothesis import given, strategies as st
 
@@ -53,7 +53,9 @@ def use_annotations(
     pass
 
 
-def use_signature(self, testA: int, testB: str = None, *, testX: float, testY: str):
+def use_signature(
+    self, testA: int, testB: str = None, *, testX: float, testY: List[str]
+):
     pass
 
 
@@ -66,9 +68,28 @@ def __init__(self, **kwargs):
         assert set(kwargs) == {"testA", "testX", "testY"}
         assert isinstance(kwargs["testA"], int)
         assert isinstance(kwargs["testX"], float)
-        assert isinstance(kwargs["testY"], str)
+        assert isinstance(kwargs["testY"], list)
+        assert all(isinstance(elem, str) for elem in kwargs["testY"])
 
 
 @given(st.builds(ModelWithAlias))
 def test_build_using_different_signature_and_annotations(val):
     assert isinstance(val, ModelWithAlias)
+
+
+def use_bad_signature(self, testA: 1, *, testX: float):
+    pass
+
+
+class ModelWithBadAliasSignature:
+    __annotations__ = get_type_hints(use_annotations)
+    __signature__ = signature(use_bad_signature)
+
+    def __init__(self, **kwargs):
+        assert set(kwargs) == {"testX"}
+        assert isinstance(kwargs["testX"], float)
+
+
+@given(st.builds(ModelWithBadAliasSignature))
+def test_build_with_non_types_in_signature(val):
+    assert isinstance(val, ModelWithBadAliasSignature)