request.url_vars property, closes #822

datasette/utils/asgi.py

@@ -32,6 +32,10 @@ class Request:
             (self.scheme, self.host, self.path, None, self.query_string, None)
         )
 
+    @property
+    def url_vars(self):
+        return (self.scope.get("url_route") or {}).get("kwargs") or {}
+
     @property
     def scheme(self):
         return self.scope.get("scheme") or "http"

docs/internals.rst

@@ -42,6 +42,9 @@ The request object is passed to various plugin hooks. It represents an incoming
 ``.args`` - MultiParams
     An object representing the parsed querystring parameters, see below.
 
+``.url_vars`` - dictionary (str -> str)
+    Variables extracted from the URL path, if that path was defined using a regular expression. See :ref:`plugin_register_routes`.
+
 ``.actor`` - dictionary (str -> Any) or None
     The currently authenticated actor (see :ref:`actors <authentication_actor>`), or ``None`` if the request is unauthenticated.
 

docs/plugins.rst

@@ -850,8 +850,8 @@ Return a list of ``(regex, async_view_function)`` pairs, something like this:
     import html
 
 
-    async def hello_from(scope):
-        name = scope["url_route"]["kwargs"]["name"]
+    async def hello_from(request):
+        name = request.url_vars["name"]
         return Response.html("Hello from {}".format(
             html.escape(name)
         ))

tests/plugins/my_plugin.py

@@ -152,8 +152,8 @@ def register_routes():
             (await datasette.get_database().execute("select 1 + 1")).first()[0]
         )
 
-    async def two(request, scope):
-        name = scope["url_route"]["kwargs"]["name"]
+    async def two(request):
+        name = request.url_vars["name"]
         greeting = request.args.get("greeting")
         return Response.text("{} {}".format(greeting, name))
 

tests/test_internals_request.py

@@ -44,3 +44,20 @@ def test_request_args():
     assert 2 == len(request.args)
     with pytest.raises(KeyError):
         request.args["missing"]
+
+
+def test_request_url_vars():
+    scope = {
+        "http_version": "1.1",
+        "method": "POST",
+        "path": "/",
+        "raw_path": b"/",
+        "query_string": b"",
+        "scheme": "http",
+        "type": "http",
+        "headers": [[b"content-type", b"application/x-www-form-urlencoded"]],
+    }
+    assert {} == Request(scope, None).url_vars
+    assert {"name": "cleo"} == Request(
+        dict(scope, url_route={"kwargs": {"name": "cleo"}}), None
+    ).url_vars