Close #13266: Add inspect.unwrap
Initial patch by Daniel Urban and Aaron Iles
diff --git a/Lib/inspect.py b/Lib/inspect.py
index 4a28507..195c9fd 100644
--- a/Lib/inspect.py
+++ b/Lib/inspect.py
@@ -360,6 +360,40 @@
"Return tuple of base classes (including cls) in method resolution order."
return cls.__mro__
+# -------------------------------------------------------- function helpers
+
+def unwrap(func, *, stop=None):
+ """Get the object wrapped by *func*.
+
+ Follows the chain of :attr:`__wrapped__` attributes returning the last
+ object in the chain.
+
+ *stop* is an optional callback accepting an object in the wrapper chain
+ as its sole argument that allows the unwrapping to be terminated early if
+ the callback returns a true value. If the callback never returns a true
+ value, the last object in the chain is returned as usual. For example,
+ :func:`signature` uses this to stop unwrapping if any object in the
+ chain has a ``__signature__`` attribute defined.
+
+ :exc:`ValueError` is raised if a cycle is encountered.
+
+ """
+ if stop is None:
+ def _is_wrapper(f):
+ return hasattr(f, '__wrapped__')
+ else:
+ def _is_wrapper(f):
+ return hasattr(f, '__wrapped__') and not stop(f)
+ f = func # remember the original func for error reporting
+ memo = {id(f)} # Memoise by id to tolerate non-hashable objects
+ while _is_wrapper(func):
+ func = func.__wrapped__
+ id_func = id(func)
+ if id_func in memo:
+ raise ValueError('wrapper loop when unwrapping {!r}'.format(f))
+ memo.add(id_func)
+ return func
+
# -------------------------------------------------- source code extraction
def indentsize(line):
"""Return the indent size, in spaces, at the start of a line of text."""
@@ -1346,6 +1380,9 @@
sig = signature(obj.__func__)
return sig.replace(parameters=tuple(sig.parameters.values())[1:])
+ # Was this function wrapped by a decorator?
+ obj = unwrap(obj, stop=(lambda f: hasattr(f, "__signature__")))
+
try:
sig = obj.__signature__
except AttributeError:
@@ -1354,13 +1391,6 @@
if sig is not None:
return sig
- try:
- # Was this function wrapped by a decorator?
- wrapped = obj.__wrapped__
- except AttributeError:
- pass
- else:
- return signature(wrapped)
if isinstance(obj, types.FunctionType):
return Signature.from_function(obj)