fix(spy): resolve source to origin of GenericAlias (#143)

Fixes #142

Author: mcous

decoy/spy_core.py

@@ -27,10 +27,10 @@ class BoundArgs(NamedTuple):
 
 
 class SpyCore:
-    """Core spy logic for mimicing a given `source` object.
+    """Core spy logic for mimicking a given `source` object.
 
     Arguments:
-        source: The source object the Spy is mimicing.
+        source: The source object the Spy is mimicking.
         name: The spec's name. If `None`, will be derived from `source`.
             Will fallback to a default value.
         module_name: The spec's module name. If left unspecified,
@@ -47,6 +47,8 @@ def __init__(
         module_name: Union[str, _FROM_SOURCE, None] = FROM_SOURCE,
         is_async: bool = False,
     ) -> None:
+        source = _resolve_source(source)
+
         self._source = source
         self._name = _get_name(source) if name is None else name
         self._module_name = (
@@ -139,6 +141,13 @@ def create_child_core(self, name: str, is_async: bool) -> "SpyCore":
         )
 
 
+def _resolve_source(source: Any) -> Any:
+    """Resolve the source object, unwrapping any generic aliases."""
+    origin = inspect.getattr_static(source, "__origin__", None)
+
+    return origin if origin is not None else source
+
+
 def _get_name(source: Any) -> str:
     """Get the name of a source object."""
     source_name = getattr(source, "__name__", None) if source is not None else None

tests/fixtures.py

@@ -1,37 +1,31 @@
 """Common test fixtures."""
 from functools import lru_cache
-from typing import Any
+from typing import Any, Generic, TypeVar
 
 
 class SomeClass:
     """Testing class."""
 
     def foo(self, val: str) -> str:
         """Get the foo string."""
-        ...
 
     def bar(self, a: int, b: float, c: str) -> bool:
         """Get the bar bool based on a few inputs."""
-        ...
 
     @staticmethod
     def fizzbuzz(hello: str) -> int:
         """Fizz some buzzes."""
-        ...
 
     def do_the_thing(self, *, flag: bool) -> None:
         """Perform a side-effect without a return value."""
-        ...
 
     @property
     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:
@@ -41,62 +35,65 @@ class SomeNestedClass:
 
     def foo(self, val: str) -> str:
         """Get the foo string."""
-        ...
 
     @property
     def child(self) -> SomeClass:
         """Get the child instance."""
-        ...
 
 
 class SomeAsyncClass:
     """Async testing class."""
 
     async def foo(self, val: str) -> str:
         """Get the foo string."""
-        ...
 
     async def bar(self, a: int, b: float, c: str) -> bool:
         """Get the bar bool based on a few inputs."""
-        ...
 
     async def do_the_thing(self, *, flag: bool) -> None:
         """Perform a side-effect without a return value."""
-        ...
 
 
 class SomeAsyncCallableClass:
     """Async callable class."""
 
     async def __call__(self, val: int) -> int:
         """Get an integer."""
-        ...
 
 
 class SomeCallableClass:
     """Async callable class."""
 
     async def __call__(self, val: int) -> int:
         """Get an integer."""
-        ...
 
 
 def noop(*args: Any, **kwargs: Any) -> Any:
     """No-op."""
-    ...
 
 
 def some_func(val: str) -> str:
     """Test function."""
-    ...
 
 
 async def some_async_func(val: str) -> str:
     """Async test function."""
-    ...
 
 
 @lru_cache(maxsize=None)
 def some_wrapped_func(val: str) -> str:
     """Wrapped test function."""
-    ...
+
+
+GenericT = TypeVar("GenericT")
+
+
+class GenericClass(Generic[GenericT]):
+    """A generic class definition."""
+
+    def hello(self, val: GenericT) -> None:
+        """Say hello."""
+
+
+ConcreteAlias = GenericClass[str]
+"""An alias with a generic type specified"""

tests/test_spy_core.py

@@ -11,6 +11,9 @@
     SomeAsyncCallableClass,
     SomeCallableClass,
     SomeNestedClass,
+    GenericClass,
+    GenericT,
+    ConcreteAlias,
     some_func,
     some_async_func,
     some_wrapped_func,
@@ -78,6 +81,16 @@ class GetNameSpec(NamedTuple):
             expected_name="SomeNestedClass.child.foo",
             expected_full_name="tests.fixtures.SomeNestedClass.child.foo",
         ),
+        GetNameSpec(
+            subject=SpyCore(source=GenericClass[int], name=None),
+            expected_name="GenericClass",
+            expected_full_name="tests.fixtures.GenericClass",
+        ),
+        GetNameSpec(
+            subject=SpyCore(source=ConcreteAlias, name=None),
+            expected_name="GenericClass",
+            expected_full_name="tests.fixtures.GenericClass",
+        ),
     ],
 )
 def test_get_name(
@@ -226,6 +239,21 @@ class GetSignatureSpec(NamedTuple):
                 return_annotation=str,
             ),
         ),
+        GetSignatureSpec(
+            subject=SpyCore(source=ConcreteAlias, name=None).create_child_core(
+                "hello", is_async=False
+            ),
+            expected_signature=inspect.Signature(
+                parameters=[
+                    inspect.Parameter(
+                        name="val",
+                        kind=inspect.Parameter.POSITIONAL_OR_KEYWORD,
+                        annotation=GenericT,
+                    )
+                ],
+                return_annotation=None,
+            ),
+        ),
     ],
 )
 def test_get_signature(