Started trying to get --asgi mode working

datasette/app.py

@@ -430,6 +430,12 @@ class Datasette:
             self.executor, sql_operation_in_thread
         )
 
+    def asgi_app(self):
+        from starlette import Router, Path
+        return Router([
+            Path('/', app=IndexView(self).asgi_app(), methods=['GET']),
+        ])
+
     def app(self):
         app = Sanic(__name__)
         default_templates = str(app_root / "datasette" / "templates")

datasette/cli.py

@@ -256,6 +256,9 @@ def package(
     "-h", "--host", default="127.0.0.1", help="host for server, defaults to 127.0.0.1"
 )
 @click.option("-p", "--port", default=8001, help="port for server, defaults to 8001")
+@click.option(
+    "--asgi", is_flag=True, help="Run in ASGI mode"
+)
 @click.option(
     "--debug", is_flag=True, help="Enable debug mode - useful for development"
 )
@@ -316,6 +319,7 @@ def serve(
     files,
     host,
     port,
+    asgi,
     debug,
     reload,
     cors,
@@ -372,4 +376,9 @@ def serve(
     )
     # Force initial hashing/table counting
     ds.inspect()
-    ds.app().run(host=host, port=port, debug=debug)
+    if asgi:
+        from uvicorn.run import UvicornServer
+        app = ds.asgi_app()
+        UvicornServer().run(app, host=host, port=port)
+    else:
+        ds.app().run(host=host, port=port, debug=debug)

datasette/views/base.py

@@ -12,6 +12,8 @@ from sanic import response
 from sanic.exceptions import NotFound
 from sanic.views import HTTPMethodView
 
+from starlette import asgi_application, Response
+
 from datasette import __version__
 from datasette.utils import (
     CustomJSONEncoder,
@@ -43,8 +45,45 @@ class DatasetteError(Exception):
         self.messagge_is_html = messagge_is_html
 
 
+class RequestWrapper:
+    # Implements the subset of the Sanic request that my code uses
+    def __init__(self, starlette_request):
+        self._request = starlette_request
+
+    @property
+    def path(self):
+        return self._request.url.path
+
+    @property
+    def query_string(self):
+        return str(self._request.query_string)
+
+    @property
+    def args(self):
+        # Key/list-of-values
+        # There's probably a better way to do this:
+        d = {}
+        for key, value in self._request.query_string:
+            d.setdefault(key, []).append(value)
+        return d
+
+    @property
+    def raw_args(self):
+        # Flat key/first-value dictionary
+        return self._request.query_string._dict
+
+
 class RenderMixin(HTTPMethodView):
 
+    def asgi_app(self):
+        @asgi_application
+        async def app(request):
+            sanic_response = await self.get(
+                RequestWrapper(request), **request["kwargs"]
+            )
+            return Response(sanic_response.body)
+        return app
+
     def render(self, templates, **context):
         template = self.ds.jinja_env.select_template(templates)
         select_templates = [