Do not require a handler function in the gateway (#9264)

* Do not require a handler function in the gateway

* test fix

Co-authored-by: Raul Jordan <raul@prysmaticlabs.com>
Co-authored-by: prylabs-bulldozer[bot] <58059840+prylabs-bulldozer[bot]@users.noreply.github.com>
(cherry picked from commit be82c87)

beacon-chain/gateway/helpers.go

@@ -1,8 +1,6 @@
 package gateway
 
 import (
-	"net/http"
-
 	gwruntime "github.com/grpc-ecosystem/grpc-gateway/v2/runtime"
 	pbrpc "github.com/prysmaticlabs/prysm/proto/beacon/rpc/v1"
 	ethpbv1 "github.com/prysmaticlabs/prysm/proto/eth/v1"
@@ -65,9 +63,6 @@ func DefaultConfig(enableDebugRPCEndpoints bool) MuxConfig {
 			},
 		}),
 	)
-	muxHandler := func(h http.Handler, w http.ResponseWriter, req *http.Request) {
-		h.ServeHTTP(w, req)
-	}
 	v1Alpha1PbHandler := gateway.PbMux{
 		Registrations: v1Alpha1Registrations,
 		Patterns:      []string{"/eth/v1alpha1/"},
@@ -80,7 +75,6 @@ func DefaultConfig(enableDebugRPCEndpoints bool) MuxConfig {
 	}
 
 	return MuxConfig{
-		Handler:       muxHandler,
 		V1PbMux:       v1PbHandler,
 		V1Alpha1PbMux: v1Alpha1PbHandler,
 	}

beacon-chain/gateway/helpers_test.go

@@ -10,7 +10,6 @@ import (
 func TestDefaultConfig(t *testing.T) {
 	t.Run("Without debug endpoints", func(t *testing.T) {
 		cfg := DefaultConfig(false)
-		assert.NotNil(t, cfg.Handler)
 		assert.NotNil(t, cfg.V1PbMux.Mux)
 		require.Equal(t, 1, len(cfg.V1PbMux.Patterns))
 		assert.Equal(t, "/eth/v1/", cfg.V1PbMux.Patterns[0])
@@ -23,7 +22,6 @@ func TestDefaultConfig(t *testing.T) {
 
 	t.Run("With debug endpoints", func(t *testing.T) {
 		cfg := DefaultConfig(true)
-		assert.NotNil(t, cfg.Handler)
 		assert.NotNil(t, cfg.V1PbMux.Mux)
 		require.Equal(t, 1, len(cfg.V1PbMux.Patterns))
 		assert.Equal(t, "/eth/v1/", cfg.V1PbMux.Patterns[0])

shared/gateway/gateway.go

@@ -131,9 +131,12 @@ func (g *Gateway) Start() {
 	}
 
 	corsMux := g.corsMiddleware(g.mux)
-	g.mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
-		g.muxHandler(corsMux, w, r)
-	})
+
+	if g.muxHandler != nil {
+		g.mux.HandleFunc("/", func(w http.ResponseWriter, r *http.Request) {
+			g.muxHandler(corsMux, w, r)
+		})
+	}
 
 	g.server = &http.Server{
 		Addr:    g.gatewayAddr,