bottle.py func_has_arg proposal

func_has_arg.py

import sys

PY3 = sys.version_info[0] == 3
PY33 = sys.version_info[0] == 3 and sys.version_info[1] >= 3

if PY33:
    from inspect import signature

    def func_has_arg(func, arg):
        return arg in signature(func).parameters

elif PY3:
    from inspect import getfullargspec

    def func_has_arg(func, arg):
        if arg in getfullargspec(func)[0]:
            return True
        closure = func.__closure__
        if closure:
            for cell in (cell for cell in closure if hasattr(cell.cell_contents, '__call__')):
                cell_contents = cell.cell_contents
                if cell_contents.__closure__:
                    if func_has_arg(cell_contents, arg):
                        return True
                if arg in getfullargspec(cell_contents)[0]:
                    return True
        return False

else:
    from inspect import getargspec

    def func_has_arg(func, arg):
        if arg in getargspec(func)[0]:
            return True
        closure = func.func_closure
        if closure:
            for cell in (cell for cell in closure if callable(cell.cell_contents)):
                cell_contents = cell.cell_contents
                if cell_contents.func_closure:
                    if func_has_arg(cell_contents, arg):
                        return True
                if arg in getargspec(cell_contents)[0]:
                    return True
        return False