Move current_async_library to different PR

httpcore/_backends/auto.py

@@ -1,14 +1,14 @@
 import typing
 from typing import Optional
 
-from .._synchronization import current_async_library
+from .._synchronization import current_async_backend
 from .base import SOCKET_OPTION, AsyncNetworkBackend, AsyncNetworkStream
 
 
 class AutoBackend(AsyncNetworkBackend):
     async def _init_backend(self) -> None:
         if not (hasattr(self, "_backend")):
-            backend = current_async_library()
+            backend = current_async_backend()
             if backend == "trio":
                 from .trio import TrioBackend
 

httpcore/_synchronization.py

@@ -1,5 +1,4 @@
 import asyncio
-import os
 import threading
 from types import TracebackType
 from typing import (
@@ -31,7 +30,6 @@
 
 
 AsyncBackend = Literal["asyncio", "trio"]
-AsyncLibrary = Literal["asyncio", "trio", "anyio"]
 
 
 def current_async_backend() -> AsyncBackend:
@@ -47,6 +45,11 @@ def current_async_backend() -> AsyncBackend:
     if environment not in ("asyncio", "trio"):  # pragma: nocover
         raise RuntimeError("Running under an unsupported async environment.")
 
+    if environment == "asyncio" and anyio is None:  # pragma: nocover
+        raise RuntimeError(
+            "Running with asyncio requires installation of 'httpcore[asyncio]'."
+        )
+
     if environment == "trio" and trio is None:  # pragma: nocover
         raise RuntimeError(
             "Running with trio requires installation of 'httpcore[trio]'."
@@ -55,18 +58,6 @@ def current_async_backend() -> AsyncBackend:
     return environment
 
 
-def current_async_library() -> AsyncLibrary:
-    if current_async_backend() == "trio":
-        return "trio"
-
-    if anyio is not None:
-        anyio_env = os.environ.get("HTTPCORE_PREFER_ANYIO", "true").lower()
-        if anyio_env in ("true", "1"):
-            return "anyio"
-
-    return "asyncio"
-
-
 class _LockProto(Protocol):
     async def acquire(self) -> Any: ...
     def release(self) -> None: ...