Lazy load Reload and Multiprocess supervisors

tests/supervisors/test_multiprocess.py

@@ -3,7 +3,7 @@
 from typing import TYPE_CHECKING, List, Optional
 
 from uvicorn import Config
-from uvicorn.supervisors import Multiprocess
+from uvicorn.supervisors.multiprocess import Multiprocess
 
 if TYPE_CHECKING:
     from asgiref.typing import ASGIReceiveCallable, ASGISendCallable, Scope

tests/test_cli.py

@@ -13,7 +13,8 @@
 from uvicorn.config import Config
 from uvicorn.main import main as cli
 from uvicorn.server import Server
-from uvicorn.supervisors import ChangeReload, Multiprocess
+from uvicorn.supervisors.multiprocess import Multiprocess
+from uvicorn.supervisors.watchfilesreload import WatchFilesReload
 
 HEADERS = "Content-Security-Policy:default-src 'self'; script-src https://example.com"
 main = importlib.import_module("uvicorn.main")
@@ -71,7 +72,7 @@ def test_cli_call_change_reload_run() -> None:
     runner = CliRunner()
 
     with mock.patch.object(Config, "bind_socket") as mock_bind_socket:
-        with mock.patch.object(ChangeReload, "run") as mock_run:
+        with mock.patch.object(WatchFilesReload, "run") as mock_run:
             result = runner.invoke(cli, ["tests.test_cli:App", "--reload"])
 
     assert result.exit_code == 0

uvicorn/main.py

@@ -27,7 +27,6 @@
     WSProtocolType,
 )
 from uvicorn.server import Server, ServerState  # noqa: F401  # Used to be defined here.
-from uvicorn.supervisors import ChangeReload, Multiprocess
 
 if typing.TYPE_CHECKING:
     from asgiref.typing import ASGIApplication
@@ -560,9 +559,14 @@ def run(
         sys.exit(1)
 
     if config.should_reload:
+        from uvicorn.supervisors import get_reload_class
+
         sock = config.bind_socket()
-        ChangeReload(config, target=server.run, sockets=[sock]).run()
+        reload_class = get_reload_class()
+        reload_class(config, target=server.run, sockets=[sock]).run()
     elif config.workers > 1:
+        from uvicorn.supervisors.multiprocess import Multiprocess
+
         sock = config.bind_socket()
         Multiprocess(config, target=server.run, sockets=[sock]).run()
     else:

uvicorn/supervisors/__init__.py

@@ -1,21 +1,23 @@
 from typing import TYPE_CHECKING, Type
 
-from uvicorn.supervisors.basereload import BaseReload
-from uvicorn.supervisors.multiprocess import Multiprocess
-
 if TYPE_CHECKING:
-    ChangeReload: Type[BaseReload]
-else:
+    from uvicorn.supervisors.basereload import BaseReload
+
+
+def get_reload_class() -> "Type[BaseReload]":
     try:
-        from uvicorn.supervisors.watchfilesreload import (
-            WatchFilesReload as ChangeReload,
-        )
+        from uvicorn.supervisors.watchfilesreload import WatchFilesReload
+
+        return WatchFilesReload
     except ImportError:  # pragma: no cover
         try:
-            from uvicorn.supervisors.watchgodreload import (
-                WatchGodReload as ChangeReload,
-            )
+            from uvicorn.supervisors.watchgodreload import WatchGodReload
+
+            return WatchGodReload
         except ImportError:
-            from uvicorn.supervisors.statreload import StatReload as ChangeReload
+            from uvicorn.supervisors.statreload import StatReload
+
+            return StatReload
+
 
-__all__ = ["Multiprocess", "ChangeReload"]
+__all__ = ["get_reload_class"]