fix: Engine initialization did not respect OS env (#2311)

Author: LeonLuttenberger

awswrangler/_distributed.py

@@ -11,8 +11,14 @@
 from importlib import reload
 from typing import Any, Callable, Dict, Literal, Optional, TypeVar, cast
 
-WR_ENGINE = os.getenv("WR_ENGINE")
-WR_MEMORY_FORMAT = os.getenv("WR_MEMORY_FORMAT")
+EngineLiteral = Literal["python", "ray"]
+MemoryFormatLiteral = Literal["pandas", "modin"]
+
+FunctionType = TypeVar("FunctionType", bound=Callable[..., Any])
+
+
+WR_ENGINE: Optional[EngineLiteral] = os.getenv("WR_ENGINE")  # type: ignore[assignment]
+WR_MEMORY_FORMAT: Optional[MemoryFormatLiteral] = os.getenv("WR_MEMORY_FORMAT")  # type: ignore[assignment]
 
 
 @unique
@@ -31,11 +37,6 @@ class MemoryFormatEnum(Enum):
     PANDAS = "pandas"
 
 
-EngineLiteral = Literal["python", "ray"]
-MemoryFormatLiteral = Literal["pandas", "modin"]
-FunctionType = TypeVar("FunctionType", bound=Callable[..., Any])
-
-
 class Engine:
     """Execution engine configuration class."""
 
@@ -111,7 +112,7 @@ def wrapper(*args: Any, **kw: Dict[str, Any]) -> Any:
     def register(cls, name: Optional[EngineLiteral] = None) -> None:
         """Register the distribution engine dispatch methods."""
         with cls._lock:
-            engine_name = cast(EngineLiteral, name or cls.get_installed().value)
+            engine_name = cast(EngineLiteral, name or cls.get().value)
             cls.set(engine_name)
             cls._registry.clear()