[bug] filter_strategy config not working

[rdettai]

Describe the bug
It seems that the filter_strategy config (which by the way is misspelled int the docs) is not taken into account when used in the Dynaconf constructor.

To Reproduce
Steps to reproduce the behavior:

1. Having the following folder structure
   Just a plain python script.

2. Having the following config files:
   No config file, just using env variables

3. Having the following app code:

Code

/test/test.py

import dynaconf

class CustomFilter:
    def __call__(self, data):
        print("this is never called")
        return {
            k: v
            for k, v in data.items()
            if k.startswith("PREFIX")
        }


if __name__ == "__main__":
    dc = dynaconf.Dynaconf(
        envvar_prefix=False,
        filter_strategy=CustomFilter(),
    )
    print(dc.as_dict())

5. Executing under the following environment

Execution

PREFIX_VAR="HELLO" OTHER_VAR="WORLD" python test.py

Expected behavior
CustomFilter should be called ("this is never called" should be displayed) and only the PREFIX_VAR should be in dict, not OTHER_VAR

Environment (please complete the following information):

• OS: Linux version 5.10.60.1-microsoft-standard-WSL2
• Dynaconf Version 3.1.9
• Framework: None

Context

I was looking for a way to filter out empty environment variables.

[limeiralucas]

I would like to fix this issue. Adding a check and execution for the filter_strategy in the env_loader seems to fix it.

diff --git a/dynaconf/loaders/env_loader.py b/dynaconf/loaders/env_loader.py
index 660bd27..3e61396 100644
--- a/dynaconf/loaders/env_loader.py
+++ b/dynaconf/loaders/env_loader.py
@@ -76,6 +76,9 @@ def load_from_env(
         }
         # Update the settings space based on gathered data from environment.
         if data:
+            filter_strategy = obj.get("FILTER_STRATEGY")
+            if filter_strategy:
+                data = filter_strategy(data)
             obj.update(data, loader_identifier=identifier)
 

Please, let me know if that's seems okay. If so, should I open a PR with the fix? 😃 (That's my first contribution to the project)

[rochacbruno]

Thanks @limeiralucas