Injection on a decorator

Hi, I really like this package and am using it in production. I was tying to mess around with decorators because I want to add side effects to a function, adding a secret_number in the example. I was expecting decorated_function_1 to work but it didn’t and I can’t wrap my head around it. Is this an expected behavior? Could injection be supported like in my_decorator_1?

I also added few examples of things I tried and only decorated_function_4 actually works.

from functools import wraps

from dependency_injector import containers, providers
from dependency_injector.wiring import Provide, inject


class Container(containers.DeclarativeContainer):
    config = providers.Configuration()


@inject
def my_decorator_1(func, secret_number: int = Provide[Container.config.secret_number]):
    @wraps(func)
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        return result + secret_number
    return wrapper

@inject
def my_decorator_2(secret_number: int = Provide[Container.config.secret_number]):
    def inner_decorator(func):
        @wraps(func)
        def wrapper(*args, **kwargs):
            result = func(*args, **kwargs)
            return result + secret_number
        return wrapper
    return inner_decorator

def my_decorator_3():
    @inject
    def inner_decorator(func, secret_number: int = Provide[Container.config.secret_number]):
        @wraps(func)
        def wrapper(*args, **kwargs):
            result = func(*args, **kwargs)
            return result + secret_number
        return wrapper
    return inner_decorator

def my_decorator_4(func):
    @wraps(func)
    def wrapper(*args, **kwargs):
        result = func(*args, **kwargs)
        secret_number = kwargs['secret_number']
        return result + secret_number
    return wrapper


@my_decorator_1
def decorated_function_1():
    return 42

@inject
@my_decorator_1
def decorated_function_1a():
    return 42

@my_decorator_2()
def decorated_function_2():
    return 42

@my_decorator_3()
def decorated_function_3():
    return 42

@inject
@my_decorator_3()
def decorated_function_3a():
    return 42

@inject
@my_decorator_4
def decorated_function_4(secret_number: int = Provide[Container.config.secret_number]):
    return 42

@my_decorator_4
@inject
def decorated_function_4a(secret_number: int = Provide[Container.config.secret_number]):
    return 42


def main():
    test_funcs = [
        decorated_function_1,
        decorated_function_1a,
        decorated_function_2, 
        decorated_function_3, 
        decorated_function_3a,
        decorated_function_4, 
        decorated_function_4a, 
    ]
    for test_f in test_funcs:
        try:
            result = test_f()
            print(f"Function {test_f} returned {result}")
        except Exception as exc:
            print(f"Function {test_f} raised {exc.__class__.__name__} '{exc}'")

if __name__ == '__main__':
    import sys

    container = Container()
    container.init_resources()
    container.config.secret_number.from_env("SECRET_INT", 24)
    container.wire(modules=[sys.modules[__name__]])

    main()

The output is:

Function <function decorated_function_1 at 0x7f93d8a4d310> raised TypeError 'unsupported operand type(s) for +: 'int' and 'Provide''
Function <function decorated_function_1a at 0x7f93d8a4d4c0> raised TypeError 'unsupported operand type(s) for +: 'int' and 'Provide''
Function <function decorated_function_2 at 0x7f93d8a4d670> raised TypeError 'unsupported operand type(s) for +: 'int' and 'Provide''
Function <function decorated_function_3 at 0x7f93d8a4d820> raised TypeError 'unsupported operand type(s) for +: 'int' and 'Provide''
Function <function decorated_function_3a at 0x7f93d8a4daf0> raised TypeError 'unsupported operand type(s) for +: 'int' and 'Provide''
Function <function decorated_function_4 at 0x7f93d8a4dca0> returned 66
Function <function decorated_function_4a at 0x7f93d8a4de50> raised KeyError ''secret_number''

[fabiocerqueira]

from functools import wraps

from dependency_injector import containers, providers
from dependency_injector.wiring import Provide, inject


class Reporter:
    def info(self, msg):
        print(f"*** [INFO] {msg}")


class Container(containers.DeclarativeContainer):
    conf = providers.Configuration()
    reporter = providers.Singleton(Reporter)


def tagger(tag):
    def inner(func):
        # @wraps(func)  # <-- using wraps break inject
        @inject
        def tagger_wrapper(text, sep=Provide[Container.conf.sep], **kwargs):
            result = func(text, **kwargs)
            return f"{result}{sep}({tag}[{func.__name__}])"

        return tagger_wrapper

    return inner


def logger(prefix):
    def inner(func):
        # @wraps(func)  # <-- using wraps break inject
        @inject
        def logger_wrapper(text, reporter=Provide[Container.reporter], **kwargs):
            result = func(text, **kwargs)
            reporter.info(f"{prefix} - {func.__name__}('{text}') was called")
            return result

        return logger_wrapper

    return inner


def helper(tag, prefix):
    def inner(func):
        @tagger(tag)
        @wraps(func)  # <-- if remove this double wraps it breaks the function name
        @logger(prefix)
        @inject
        @wraps(func)
        def helper_wrapper(text, **kwargs):
            result = func(text, **kwargs)
            return result

        return helper_wrapper

    return inner


@helper("my_tag", "|my_prefix|")
def my_example(text):
    return text


if __name__ == "__main__":
    container = Container()
    container.wire(modules=[__name__])
    container.conf.from_dict({"sep": " / "})
    print(my_example("hi!"))

Running the example above we get the expected behaviour

*** [INFO] |my_prefix| - my_example('hi!') was called
hi! / (my_tag[my_example])

If you try to remove this double @wraps call in helper the function name breaks:

*** [INFO] |my_prefix| - my_example('hi!') was called
hi! / (my_tag[logger_wrapper])
              ^^^^^^^^^^^^^^^^

if I move the @wraps to the decorator(this I think should be the correct way) it breaks @inject

Traceback (most recent call last):
  File "example.py", line 69, in <module>
    print(my_example("hi!"))
  File "/home/fabio/.pyenv/versions/.../dependency_injector/wiring.py", line 612, in _patched
    result = fn(*args, **to_inject)
  File "example.py", line 22, in tagger_wrapper
    result = func(text, **kwargs)
  File "/home/fabio/.pyenv/versions/.../dependency_injector/wiring.py", line 612, in _patched
    result = fn(*args, **to_inject)
  File "example.py", line 36, in logger_wrapper
    reporter.info(f"{prefix} - {func.__name__}('{text}') was called")
AttributeError: 'Provide' object has no attribute 'info'

[rmk135]

I have the fix! Working on merging it to develop.