- modified instrospection in an attempt to resolve issue 55;

src/slipcover/slipcover.py

@@ -622,12 +622,13 @@ def print_coverage(self, outfile=sys.stdout, *, missing_width=None) -> None:
 
     @staticmethod
     def find_functions(items, visited : set):
-        import inspect
+        # Don't use isinstance() or inspect.isfunction, as isinstance as may call __class__,
+        # which may have side effects (e.g., using Celery https://github.com/celery/celery).
         def is_patchable_function(func):
             # PyPy has no "builtin functions" like CPython. instead, it uses
             # regular functions, with a special type of code object.
             # the second condition is always True on CPython
-            return inspect.isfunction(func) and type(func.__code__) is types.CodeType
+            return issubclass(type(func), types.FunctionType) and type(func.__code__) is types.CodeType
 
         def find_funcs(root):
             if is_patchable_function(root):
@@ -637,7 +638,7 @@ def find_funcs(root):
 
             # Prefer isinstance(x,type) over isclass(x) because many many
             # things, such as str(), are classes
-            elif isinstance(root, type):
+            elif issubclass(type(root), type):
                 if root not in visited:
                     visited.add(root)
 
@@ -653,7 +654,7 @@ def find_funcs(root):
                                 yield from find_funcs(base.__dict__[obj_key])
                                 break
 
-            elif (isinstance(root, classmethod) or isinstance(root, staticmethod)) and \
+            elif (issubclass(type(root), classmethod) or issubclass(type(root), staticmethod)) and \
                  is_patchable_function(root.__func__):
                 if root.__func__ not in visited:
                     visited.add(root.__func__)

tests/test_instrumentation.py

@@ -626,13 +626,14 @@ def foo(n):
     assert old_code == foo.__code__, "Code de-instrumented"
 
 
+def func_names(funcs):
+    # pytest-asyncio > 0.21.1 adds __pytest_asyncio_... event loop functions
+    return sorted([f.__name__ for f in funcs if f.__name__ != 'scoped_event_loop'])
+
+
 def test_find_functions():
     import class_test as t
 
-    def func_names(funcs):
-        # pytest-asyncio > 0.21.1 adds __pytest_asyncio_... event loop functions
-        return sorted([f.__name__ for f in funcs if f.__name__ != 'scoped_event_loop'])
-
     assert ["b", "b_classm", "b_static", "f1", "f2", "f3", "f4", "f5", "f7",
             "f_classm", "f_static"] == \
            func_names(sc.Slipcover.find_functions(t.__dict__.values(), set()))
@@ -655,3 +656,17 @@ def func_names(funcs):
                                                   visited))
 
 
+def test_find_functions_class_side_effect():
+    # Celery overrides __class__ in ways that cause side effects -- see issue 55
+    class A:
+        @property
+        def __class__(self):
+            raise RuntimeError("We don't want this called")
+
+    class B:
+        foo = A()
+
+        def bar(self):
+            pass
+
+    assert ["bar"] == func_names(sc.Slipcover.find_functions(B.__dict__.values(), set()))