[bug] Lazy validation fails with TypeError: __call__() takes 2 positional arguments but 3 were given

Describe the bug Tried to introduce Lazy Validators as described in https://www.dynaconf.com/validation/#computed-values i.e.

from dynaconf.utils.parse_conf import empty, Lazy

Validator("FOO", default=Lazy(empty, formatter=my_function))

First bug (documentation): The above fails with ImportError: cannot import name 'empty' from 'dynaconf.utils.parse_conf' –> “empty” seems to be now in dynaconf.utils.functional.empty

Second bug: Lazy Validator fails with TypeError: __call__() takes 2 positional arguments but 3 were given

To Reproduce Steps to reproduce the behavior:

from dynaconf.utils.parse_conf import Lazy
from dynaconf.utils.functional import empty

def lazy_foobar(s, v):
    return "foobar"

from dynaconf import Dynaconf
s = Dynaconf(
    validators=[Validator("FOOBAR", default=Lazy(empty, formatter=lazy_foobar)),],
)
print(s.FOOBAR)

stacktrace:

    print(s.FOOBAR)
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\base.py", line 113, in __getattr__
    self._setup()
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\base.py", line 164, in _setup
    settings_module=settings_module, **self._kwargs
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\base.py", line 236, in __init__
    only=self._validate_only, exclude=self._validate_exclude
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\validator.py", line 417, in validate
    validator.validate(self.settings, only=only, exclude=exclude)
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\validator.py", line 198, in validate
    settings, settings.current_env, only=only, exclude=exclude
  File "c:\ta\virtualenv\dconf\lib\site-packages\dynaconf\validator.py", line 227, in _validate_items
    if callable(self.default)
TypeError: __call__() takes 2 positional arguments but 3 were given

Expected behavior Work as documented in https://www.dynaconf.com/validation/#computed-values

Environment (please complete the following information):

• OS: Windows 10 Pro
• Dynaconf Version: 3.1.7 (also 3.1.4)
• Frameworks in use: N/A

Additional context Add any other context about the problem here.

[rochacbruno]

Hi @GibranHL0

My suggestions

on utils/parse_conf.py

# make the default value for Lazy to be an empty value
11  from dynaconf.utils.functional import empty
169  def __init__(self, value=empty, formatter=Formatters.python_formatter):

# accept a `validator_object` as named parameter and bind it to the context
178  def __call__(self, settings, validator_object=None):
         """LazyValue triggers format lazily."""
        self.settings = settings
        self.context["_validator_object"] = validator_object
        return self.formatter(self.value, **self.context)

Then, update the documentation on https://www.dynaconf.com/validation/#computed-values (docs/validation.md)

the correct way of using the computed lazy value must be

from dynaconf import Dynaconf, Validator
from dynaconf.utils.parse_conf import Lazy


def my_lazy_function(value, **context):
    """
    value: default value passed to the validator, defaults to `empty`
    context: a dictionary containing
             env: All the environment variables
             this: The settings instance
    """
    # Hypothetical example
    if env.get("HOSTNAME") == "localhost":
        result = f"{this.server.name}/local"
    else:
        result = f"{this.server.name}/{value}"
    return result


settings = Dynaconf(
    validators=[
        Validator("FOOBAR", default=Lazy("default_optional_value", formatter=my_lazy_function))
    ]
)

# When the value is first accessed, then the my_lazy_function will be called
print(settings.FOOBAR)

[GibranHL0]

Hi 👋

I’d like to be assigned to this issue and give it a try.