Make HTTP middleware easier to use

appengine/cmd/dm/frontend/init.go

Index: appengine/cmd/dm/frontend/init.go
diff --git a/appengine/cmd/dm/frontend/init.go b/appengine/cmd/dm/frontend/init.go
index 1a6d0c55fac6d675e28c6721d20f9591a0a6ec44..ca3a81cb2b1796a3865ae4ce685248399cf2ede2 100644
--- a/appengine/cmd/dm/frontend/init.go
+++ b/appengine/cmd/dm/frontend/init.go
@@ -7,9 +7,6 @@ package frontend
 import (
 	"net/http"
 
-	"golang.org/x/net/context"
-
-	"github.com/julienschmidt/httprouter"
 	"github.com/luci/luci-go/appengine/cmd/dm/deps"
 	"github.com/luci/luci-go/appengine/gaeconfig"
 	"github.com/luci/luci-go/appengine/gaemiddleware"
@@ -17,37 +14,38 @@ import (
 	"github.com/luci/luci-go/common/config"
 	"github.com/luci/luci-go/common/logging"
 	"github.com/luci/luci-go/server/discovery"
-	"github.com/luci/luci-go/server/middleware"
 	"github.com/luci/luci-go/server/prpc"
+	"github.com/luci/luci-go/server/router"
 )
 
-func base(h middleware.Handler) httprouter.Handle {
-	newH := func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-		cfg, err := gaeconfig.New(c)
-		switch err {
-		case nil:
-			c = config.Set(c, cfg)
-		case gaeconfig.ErrNotConfigured:
-			logging.Warningf(c, "luci-config service url not configured. Configure this at /admin/settings/gaeconfig.")
-		default:
-			panic(err)
-		}
-		h(c, rw, r, p)
-	}
-	return gaemiddleware.BaseProd(newH)
+func base() []router.Handler {
+	return append(
+		gaemiddleware.BaseProd(),
+		func(c *router.Context) {
+			cfg, err := gaeconfig.New(c.Context)
+			switch err {
+			case nil:
+				c.Context = config.Set(c.Context, cfg)
+			case gaeconfig.ErrNotConfigured:
+				logging.Warningf(c.Context, "luci-config service url not configured. Configure this at /admin/settings/gaeconfig.")
+			default:
+				panic(err)
+			}
+		},
+	)
 }
 
 func init() {
-	router := httprouter.New()
+	r := router.New()
 	tmb := tumble.Service{}
 
 	svr := prpc.Server{}
 	deps.RegisterDepsServer(&svr)
 	discovery.Enable(&svr)
 
-	svr.InstallHandlers(router, base)
-	tmb.InstallHandlers(router)
-	gaemiddleware.InstallHandlers(router, base)
+	svr.InstallHandlers(r, base())
+	tmb.InstallHandlers(r)
+	gaemiddleware.InstallHandlers(r, base())
 
-	http.Handle("/", router)
+	http.Handle("/", r)
 }