Replace deprecated inspect.formatargspec

Python 3.7 raises a deprecation warning:

salt/utils/decorators/signature.py:31: DeprecationWarning:
`formatargspec` is deprecated since Python 3.5. Use `signature` and the
`Signature` object directly

`inspect.formatargspec` is only used in
`salt.utils.decorators.signature.identical_signature_wrapper` which is
only used in `salt.utils.decorators.path` for decorating the `which` and
`which_bin` functions. The function `identical_signature_wrapper` can be
simply replaced by Python's `functools.wraps` which is available since
at least Python 2.7.

When inspecting those wrapped functions, the underlying function (stored
in the `__wrapped__` attribute) needs to be inspect instead.

fixes #50911
Signed-off-by: Benjamin Drung <benjamin.drung@cloud.ionos.com>

salt/utils/args.py

@@ -244,7 +244,12 @@ def yamlify_arg(arg):
 
 def get_function_argspec(func, is_class_method=None):
     """
-    A small wrapper around getargspec that also supports callable classes
+    A small wrapper around getargspec that also supports callable classes and wrapped functions
+
+    If the given function is a wrapper around another function (i.e. has a
+    ``__wrapped__`` attribute), return the functions specification of the underlying
+    function.
+
     :param is_class_method: Pass True if you are sure that the function being passed
                             is a class method. The reason for this is that on Python 3
                             ``inspect.ismethod`` only returns ``True`` for bound methods,
@@ -256,6 +261,9 @@ def get_function_argspec(func, is_class_method=None):
     if not callable(func):
         raise TypeError("{0} is not a callable".format(func))
 
+    if hasattr(func, "__wrapped__"):
+        func = func.__wrapped__
+
     if is_class_method is True:
         aspec = _getargspec(func)
         del aspec.args[0]  # self

salt/utils/decorators/path.py

@@ -4,10 +4,11 @@ Decorators for salt.utils.path
 """
 from __future__ import absolute_import, print_function, unicode_literals
 
+import functools
+
 # Import Salt libs
 import salt.utils.path
 from salt.exceptions import CommandNotFoundError
-from salt.utils.decorators.signature import identical_signature_wrapper
 
 
 def which(exe):
@@ -16,6 +17,7 @@ def which(exe):
     """
 
     def wrapper(function):
+        @functools.wraps(function)
         def wrapped(*args, **kwargs):
             if salt.utils.path.which(exe) is None:
                 raise CommandNotFoundError(
@@ -23,7 +25,7 @@ def which(exe):
                 )
             return function(*args, **kwargs)
 
-        return identical_signature_wrapper(function, wrapped)
+        return wrapped
 
     return wrapper
 
@@ -34,6 +36,7 @@ def which_bin(exes):
     """
 
     def wrapper(function):
+        @functools.wraps(function)
         def wrapped(*args, **kwargs):
             if salt.utils.path.which_bin(exes) is None:
                 raise CommandNotFoundError(
@@ -42,6 +45,6 @@ def which_bin(exes):
                 )
             return function(*args, **kwargs)
 
-        return identical_signature_wrapper(function, wrapped)
+        return wrapped
 
     return wrapper

salt/utils/decorators/signature.py

@@ -1,44 +0,0 @@
-# -*- coding: utf-8 -*-
-"""
-A decorator which returns a function with the same signature of the function
-which is being wrapped.
-"""
-# Import Python libs
-from __future__ import absolute_import, print_function, unicode_literals
-
-import inspect
-from functools import wraps
-
-# Import Salt libs
-import salt.utils.args
-
-# Import 3rd-party libs
-from salt.ext import six
-
-
-def identical_signature_wrapper(original_function, wrapped_function):
-    """
-    Return a function with identical signature as ``original_function``'s which
-    will call the ``wrapped_function``.
-    """
-    context = {"__wrapped__": wrapped_function}
-    function_def = compile(
-        "def {0}({1}):\n"
-        "    return __wrapped__({2})".format(
-            # Keep the original function name
-            original_function.__name__,
-            # The function signature including defaults, i.e., 'timeout=1'
-            inspect.formatargspec(
-                *salt.utils.args.get_function_argspec(original_function)
-            )[1:-1],
-            # The function signature without the defaults
-            inspect.formatargspec(
-                formatvalue=lambda val: "",
-                *salt.utils.args.get_function_argspec(original_function)
-            )[1:-1],
-        ),
-        "<string>",
-        "exec",
-    )
-    six.exec_(function_def, context)
-    return wraps(original_function)(context[original_function.__name__])