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 8075b6155a0c83783d038eaa4b491113012544fa..2ad63c77119dc72f12f82987fdeeab614127518c 100644
--- a/appengine/cmd/dm/frontend/init.go
+++ b/appengine/cmd/dm/frontend/init.go
@@ -6,92 +6,98 @@ package frontend
 
 import (
 	"fmt"
 	"net/http"
 	"os"
 
 	"golang.org/x/net/context"
 
 	"google.golang.org/appengine"
 
-	"github.com/julienschmidt/httprouter"
 	"github.com/luci/luci-go/appengine/cmd/dm/deps"
 	"github.com/luci/luci-go/appengine/cmd/dm/distributor"
 	"github.com/luci/luci-go/appengine/cmd/dm/mutate"
 	"github.com/luci/luci-go/appengine/gaeconfig"
 	"github.com/luci/luci-go/appengine/gaemiddleware"
 	"github.com/luci/luci-go/appengine/tumble"
 	"github.com/luci/luci-go/common/config"
 	"github.com/luci/luci-go/common/config/impl/filesystem"
 	"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 addConfigProd(c context.Context) context.Context {
 	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.")
 		fallthrough
 	default:
 		panic(err)
 	}
 	return c
 }
 
-func baseProd(h middleware.Handler) httprouter.Handle {
-	newH := func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-		h(addConfigProd(c), rw, r, p)
-	}
-	return gaemiddleware.BaseProd(newH)
+func baseProd() router.MiddlewareChain {
+	return append(
+		gaemiddleware.BaseProd(),
+		func(c *router.Context, next router.Handler) {
+			c.Context = addConfigProd(c.Context)
+			next(c)
+		},
+	)
 }
 
 func addConfigDev(c context.Context) context.Context {
 	fpath := os.Getenv("LUCI_DM_CONFIG_BASE_PATH")
 	if fpath == "" {
 		panic(fmt.Errorf("LUCI_DM_CONFIG_BASE_PATH must be set in the environment"))
 	}
 	fs, err := filesystem.New(fpath)
 	if err != nil {
 		panic(fmt.Errorf("while setting up LUCI_DM_CONFIG_BASE_PATH: %s", err))
 	}
 	return config.Set(c, fs)
 }
 
-func baseDev(h middleware.Handler) httprouter.Handle {
-	return gaemiddleware.BaseProd(func(c context.Context, rw http.ResponseWriter, r *http.Request, p httprouter.Params) {
-		h(addConfigDev(c), rw, r, p)
-	})
+func baseDev() router.MiddlewareChain {
+	return append(
+		gaemiddleware.BaseProd(),
+		func(c *router.Context, next router.Handler) {
+			c.Context = addConfigDev(c.Context)
+			next(c)
+		},
+	)
 }
 
 func init() {
-	router := httprouter.New()
+	r := router.New()
 	tmb := tumble.Service{}
 
 	reg := distributor.NewRegistry(nil, mutate.FinishExecutionFn)
 
-	base := baseProd
+	basemw := baseProd()
 	tmb.Middleware = func(c context.Context) context.Context {
 		return distributor.WithRegistry(addConfigProd(c), reg)
 	}
 	if appengine.IsDevAppServer() {
-		base = baseDev
+		basemw = baseDev()
 		tmb.Middleware = func(c context.Context) context.Context {
 			return distributor.WithRegistry(addConfigDev(c), reg)
 		}
 	}
 
-	distributor.InstallHandlers(reg, router, base)
+	distributor.InstallHandlers(reg, r, basemw)
 
 	svr := prpc.Server{}
 	deps.RegisterDepsServer(&svr, reg)
 	discovery.Enable(&svr)
-	svr.InstallHandlers(router, base)
-	tmb.InstallHandlers(router)
-	gaemiddleware.InstallHandlers(router, base)
+	svr.InstallHandlers(r, basemw)
+	tmb.InstallHandlers(r)
+	gaemiddleware.InstallHandlers(r, basemw)
 
-	http.Handle("/", router)
+	http.Handle("/", r)
 }