add result pattern including relevant test cases

src/dopt_basics/result_pattern.py

@@ -1,16 +1,21 @@
+from __future__ import annotations
+
 import dataclasses as dc
 import inspect
 import typing as t
 from collections.abc import Callable
 from functools import wraps
-from logging import Logger
+from typing import TYPE_CHECKING
+
+if TYPE_CHECKING:
+    from logging import Logger
 
 P = t.ParamSpec("P")
 T = t.TypeVar("T")
 
 
 # ** Exceptions for result wrappers
-class WAccessResultDespiteError(Exception):
+class WrapperAccessResultDespiteError(Exception):
     """wrapped results exception: raised if result is accessed, even though
     there was an error in the underlying procedure"""
 
@@ -24,6 +29,8 @@ class Status:
 
 
 class StatusHandler:
+    __slots__ = ("logger", "_SUCCESS")
+
     def __init__(
         self,
         logger: Logger | None = None,
@@ -120,15 +127,18 @@ STATUS_HANDLER: t.Final[StatusHandler] = StatusHandler()
 
 
 class ResultWrapper(t.Generic[T]):
+    __slots__ = ("_result", "status")
+
     def __init__(
         self,
         result: T | NotSet,
         exception: Exception | None,
         code_on_error: int,
     ) -> None:
-        assert (isinstance(result, NotSet) and exception is not None) or (
-            not isinstance(result, NotSet) and exception is None
-        ), "set >NotSet< without exception or result with exception"
+        if isinstance(result, NotSet) and exception is None:
+            raise ValueError("[ResultWrapper] Set >NotSet< without exception")
+        elif not isinstance(result, NotSet) and exception is not None:
+            raise ValueError("[ResultWrapper] Set result with exception")
 
         self._result = result
         status: Status = STATUS_HANDLER.SUCCESS
@@ -139,7 +149,9 @@ class ResultWrapper(t.Generic[T]):
     @property
     def result(self) -> T:
         if isinstance(self._result, NotSet):
-            raise WAccessResultDespiteError("Can not access result because it is not set")
+            raise WrapperAccessResultDespiteError(
+                "Can not access result because it is not set"
+            )
         return self._result
 
     def __str__(self) -> str: