Fix hard dependency on anyio

Author: smurfix

pyproject.toml

@@ -1,6 +1,6 @@
 [project]
 name = "asyncclick"
-version = "8.2.2.1"
+version = "8.2.2.2"
 description = "Composable command line interface toolkit, async fork"
 readme = "README.md"
 license = "BSD-3-Clause"
@@ -16,7 +16,6 @@ classifiers = [
 requires-python = ">=3.11"
 dependencies = [
     "colorama; platform_system == 'Windows'",
-    "anyio",
 ]
 
 [project.urls]
@@ -35,6 +34,12 @@ docs = [
     "sphinx-tabs",
     "sphinxcontrib-log-cabinet",
 ]
+anyio = [
+    "anyio",
+]
+trio = [
+    "trio",
+]
 docs-auto = [
     "sphinx-autobuild",
 ]

src/click/core.py

@@ -21,8 +21,6 @@
 from itertools import repeat
 from types import TracebackType
 
-import anyio
-
 from . import types
 from .exceptions import Abort
 from .exceptions import BadParameter
@@ -1508,7 +1506,21 @@ def __call__(self, *args: t.Any, _anyio_backend=None, **kwargs: t.Any) -> t.Any:
             import asyncclick
 
             _anyio_backend = asyncclick.anyio_backend
-        return anyio.run(self._main, main, args, kwargs, backend=_anyio_backend)
+
+        try:
+            import anyio
+        except ImportError:
+            pass
+        else:
+            return anyio.run(self._main, main, args, kwargs, backend=_anyio_backend)
+        if _anyio_backend == "trio":
+            import trio
+            return trio.run(self._main, main, args, kwargs)
+        if _anyio_backend == "asyncio":
+            import asyncio
+            return asyncio.run(self._main(main, args, kwargs))
+        raise RuntimeError(f"Backend {_anyio_backend !r} unknown")
+
 
     async def _main(self, main, args, kwargs):
         return await main(*args, **kwargs)