How to write a wrapper around these functions?

[oliversheridanmethven]

jsobj returns a dictionary. If I wanted to write a decorator which returns the .items() of whatever it is decorating (presumably a function which returns dictionaries), how would I do this, as my naive implementation didn't work. Can the functions in this module even be decorated in "the usual" manner?

My attempt:

from varname.helpers import jsobj
from functools import wraps
import unittest

def return_dict_items(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs).items()
    return wrapper

class TestWrapper(unittest.TestCase):
    def test_wrapper(self):
        foo = return_dict_items(jsobj)
        a = 1
        self.assertEqual([("a", 1)], list(foo(a)))


if __name__ == '__main__':
    unittest.main()

However:

Expected :[('a', 1)]
Actual   :[(<ast.Starred object at 0x10b96f850>, 1)]

[pwwang]

Consider how jsobj was actually implemented:

def jsobj(*args: Any, vars_only: bool = True, **kwargs: Any) -> Dict[str, Any]:
    argnames: Tuple[str, ...] = argname("args", vars_only=vars_only)
    out = dict(zip(argnames, args))
    out.update(kwargs)
    return out

When you wrap jsobj, then the default frame passed to argname is not 1 anymore, you will need to implement a new jsobj by yourself by passing frame=2 to argname:

from varname import argname
from varname.helpers import jsobj
from functools import wraps
import unittest


def jsobj_to_be_wrapped(*args, vars_only=True, **kwargs):
    argnames = argname("args", vars_only=vars_only, frame=2)
    out = dict(zip(argnames, args))
    out.update(kwargs)
    return out


def return_dict_items(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs).items()
    return wrapper

class TestWrapper(unittest.TestCase):
    def test_wrapper(self):
        foo = return_dict_items(jsobj_to_be_wrapped)
        a = 1
        self.assertEqual([("a", 1)], list(foo(a)))


if __name__ == '__main__':
    unittest.main()

[oliversheridanmethven]

Seems a little "off" to have two versions of a function, one that can be wrapped and another which can't, but considering playing about with frames and stacks and the like is always a bit "hacky" it's not the end of the world.

[oliversheridanmethven]

Also, this has the drawback that this needs to know how many times it will be decorated, and I can't decorate it indefinitely (or not at all).

[pwwang]

The frame argument was added to v0.13.3:

def myjsobj(*args, **kwargs):
    return jsobj(*args, vars_only=False, frame=2, **kwargs)

x = lambda: None
x.b = 2
obj = myjsobj(x.b)
assert obj == {"x.b": 2}

[pwwang]

Here is now it works in your case:

from varname.helpers import jsobj
from functools import wraps
import unittest

def return_dict_items(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        return func(*args, **kwargs, vars_only=False, frame=2).items()
    return wrapper

class TestWrapper(unittest.TestCase):
    def test_wrapper(self):
        foo = return_dict_items(jsobj)
        a = 1
        self.assertEqual([("a", 1)], list(foo(a)))


if __name__ == '__main__':
    unittest.main()

[oliversheridanmethven]

Perfect.