Wrapped Env Override Decorator

env_override.py

import inspect
import os
from functools import wraps

def env_override(func):
    sig = inspect.signature(func)
    # Identify parameters with default value None
    none_defaults = [
        name for name, param in sig.parameters.items()
        if param.default is None
    ]

    @wraps(func)
    def wrapper(*args, **kwargs):
        # Bind the arguments to the function's signature
        bound_args = sig.bind_partial(*args, **kwargs)
        bound_args.apply_defaults()

        for name in none_defaults:
            # Check if the argument is missing or None
            if name not in bound_args.arguments or bound_args.arguments[name] is None:
                # Look up the environment variable
                env_value = os.environ.get(name)
                if env_value is not None:
                    param = sig.parameters[name]
                    # Attempt to cast the environment variable to the annotated type
                    if param.annotation != inspect.Parameter.empty:
                        try:
                            bound_args.arguments[name] = param.annotation(env_value)
                        except Exception as e:
                            raise ValueError(
                                f"Could not convert environment variable '{name}' to {param.annotation}"
                            ) from e
                    else:
                        bound_args.arguments[name] = env_value

        # Call the original function with updated arguments
        return func(*bound_args.args, **bound_args.kwargs)

    return wrapper