fix(spy): follow __wrapped__ when getting specs and signatures (#134)

Fixes #133

decoy/spec.py

@@ -74,7 +74,7 @@ def get_signature(self) -> Optional[inspect.Signature]:
         source = self._get_source()
 
         try:
-            return inspect.signature(source)
+            return inspect.signature(source, follow_wrapped=True)
         except (ValueError, TypeError):
             return None
 
@@ -130,10 +130,13 @@ def get_child_spec(self, name: str) -> "Spec":
             elif isinstance(child_source, staticmethod):
                 child_source = child_source.__func__
 
-            elif inspect.isfunction(child_source):
-                # consume the `self` argument of the method to ensure proper
-                # signature reporting by wrapping it in a partial
-                child_source = functools.partial(child_source, None)
+            else:
+                child_source = inspect.unwrap(child_source)
+
+                if inspect.isfunction(child_source):
+                    # consume the `self` argument of the method to ensure proper
+                    # signature reporting by wrapping it in a partial
+                    child_source = functools.partial(child_source, None)
 
         return Spec(source=child_source, name=child_name, module_name=self._module_name)
 

tests/common.py

@@ -1,4 +1,5 @@
 """Common test interfaces."""
+from functools import lru_cache
 from typing import Any
 
 
@@ -27,6 +28,11 @@ def primitive_property(self) -> str:
         """Get a primitive computed property."""
         ...
 
+    @lru_cache(maxsize=None)
+    def some_wrapped_method(self, val: str) -> str:
+        """Get a thing through a wrapped method."""
+        ...
+
 
 class SomeNestedClass:
     """Nested testing class."""
@@ -75,17 +81,22 @@ async def __call__(self, val: int) -> int:
         ...
 
 
-# NOTE: these `Any`s are forward references for call signature testing purposes
 def noop(*args: Any, **kwargs: Any) -> Any:
     """No-op."""
-    pass
+    ...
 
 
 def some_func(val: str) -> str:
     """Test function."""
-    return "can't touch this"
+    ...
 
 
 async def some_async_func(val: str) -> str:
     """Async test function."""
-    return "can't touch this"
+    ...
+
+
+@lru_cache(maxsize=None)
+def some_wrapped_func(val: str) -> str:
+    """Wrapped test function."""
+    ...

tests/test_spec.py

@@ -13,6 +13,7 @@
     SomeNestedClass,
     some_func,
     some_async_func,
+    some_wrapped_func,
 )
 
 
@@ -184,6 +185,34 @@ class GetSignatureSpec(NamedTuple):
                 return_annotation=int,
             ),
         ),
+        GetSignatureSpec(
+            subject=Spec(source=some_wrapped_func, name=None),
+            expected_signature=inspect.Signature(
+                parameters=[
+                    inspect.Parameter(
+                        name="val",
+                        kind=inspect.Parameter.POSITIONAL_OR_KEYWORD,
+                        annotation=str,
+                    )
+                ],
+                return_annotation=str,
+            ),
+        ),
+        GetSignatureSpec(
+            subject=Spec(source=SomeClass, name=None).get_child_spec(
+                "some_wrapped_method"
+            ),
+            expected_signature=inspect.Signature(
+                parameters=[
+                    inspect.Parameter(
+                        name="val",
+                        kind=inspect.Parameter.POSITIONAL_OR_KEYWORD,
+                        annotation=str,
+                    )
+                ],
+                return_annotation=str,
+            ),
+        ),
     ],
 )
 def test_get_signature(
@@ -315,6 +344,13 @@ class GetBindArgsSpec(NamedTuple):
             expected_args=("hello",),
             expected_kwargs={},
         ),
+        GetBindArgsSpec(
+            subject=Spec(source=some_wrapped_func, name=None),
+            input_args=(),
+            input_kwargs={"val": "hello"},
+            expected_args=("hello",),
+            expected_kwargs={},
+        ),
     ],
 )
 def test_bind_args(