Support ASGI3

daphne/cli.py

@@ -1,4 +1,7 @@
+import asyncio
 import argparse
+import functools
+import inspect
 import logging
 import sys
 from argparse import ArgumentError, Namespace
@@ -14,6 +17,17 @@ DEFAULT_HOST = "127.0.0.1"
 DEFAULT_PORT = 8000
 
 
+class ASGI3Middleware:
+    def __init__(self, app):
+        self.app = app
+
+    def __call__(self, scope):
+        return functools.partial(self.asgi, scope=scope)
+
+    async def asgi(self, receive, send, scope):
+        await self.app(scope, receive, send)
+
+
 class CommandLineInterface(object):
     """
     Acts as the main CLI entry point for running the server.
@@ -113,6 +127,13 @@ class CommandLineInterface(object):
             help="The WebSocket protocols you wish to support",
             default=None,
         )
+        self.parser.add_argument(
+            "--asgi-protocol",
+            dest="asgi_protocol",
+            help="The version of the ASGI protocol to use",
+            default="auto",
+            choices=["asgi2", "asgi3", "auto"]
+        )
         self.parser.add_argument(
             "--root-path",
             dest="root_path",
@@ -198,6 +219,23 @@ class CommandLineInterface(object):
         if args.proxy_headers:
             return "X-Forwarded-Port"
 
+    def _guess_asgi_protocol(self, application):
+        if getattr(application, "_asgi_single_callable", False):
+            return "asgi3"
+        if getattr(application, "_asgi_double_callable", False):
+            return "asgi2"
+        # Uninstanted classes are double-callable
+        if inspect.isclass(application):
+            return "asgi2"
+        # Instanted classes depend on their __call__
+        if hasattr(application, "__call__"):
+            # We only check to see if its __call__ is a coroutine function -
+            # if it's not, it still might be a coroutine function itself.
+            if asyncio.iscoroutinefunction(application.__call__):
+                return "asgi3"
+        # Non-classes we just check directly
+        return "asgi3" if asyncio.iscoroutinefunction(application) else "asgi2"
+
     def run(self, args):
         """
         Pass in raw argument list and it will decode them
@@ -227,6 +265,14 @@ class CommandLineInterface(object):
         # Import application
         sys.path.insert(0, ".")
         application = import_by_path(args.application)
+
+        asgi_protocol = args.asgi_protocol
+        if asgi_protocol == "auto":
+            asgi_protocol = self._guess_asgi_protocol(application)
+
+        if asgi_protocol == "asgi3":
+            application = ASGI3Middleware(application)
+
         # Set up port/host bindings
         if not any(
             [