Clean up the rpc.serverInfo implementation.

- Remove the RPCServerInfo client helper, it was unused outside tests.
- Remove the methodFunc wrapper type, it is no longer necessary.
- Fix up tests.

internal_test.go

@@ -167,7 +167,7 @@ func TestClient_contextCancellation(t *testing.T) {
 	stopped := make(chan struct{})
 	cpipe, spipe := channel.Direct()
 	srv := NewServer(hmap{
-		"Hang": methodFunc(func(ctx context.Context, _ *Request) (any, error) {
+		"Hang": Handler(func(ctx context.Context, _ *Request) (any, error) {
 			close(started) // signal that the method handler is running
 			select {
 			case <-stopped:
@@ -219,10 +219,10 @@ func TestServer_specialMethods(t *testing.T) {
 	defer leaktest.Check(t)()
 
 	s := NewServer(hmap{
-		"rpc.nonesuch": methodFunc(func(context.Context, *Request) (any, error) {
+		"rpc.nonesuch": Handler(func(context.Context, *Request) (any, error) {
 			return "OK", nil
 		}),
-		"donkeybait": methodFunc(func(context.Context, *Request) (any, error) {
+		"donkeybait": Handler(func(context.Context, *Request) (any, error) {
 			return true, nil
 		}),
 	}, nil)
@@ -243,7 +243,7 @@ func TestServer_disableBuiltinHook(t *testing.T) {
 	defer leaktest.Check(t)()
 
 	s := NewServer(hmap{
-		"rpc.nonesuch": methodFunc(func(context.Context, *Request) (any, error) {
+		"rpc.nonesuch": Handler(func(context.Context, *Request) (any, error) {
 			return "OK", nil
 		}),
 	}, &ServerOptions{DisableBuiltin: true})
@@ -270,7 +270,7 @@ func TestBatchReply(t *testing.T) {
 
 	cpipe, spipe := channel.Direct()
 	srv := NewServer(hmap{
-		"test": methodFunc(func(_ context.Context, req *Request) (any, error) {
+		"test": Handler(func(_ context.Context, req *Request) (any, error) {
 			return req.Method() + " OK", nil
 		}),
 	}, nil).Start(spipe)

jrpc2_test.go

@@ -1081,9 +1081,9 @@ func TestRPCServerInfo(t *testing.T) {
 	loc := server.NewLocal(handler.Map{"Test": testOK}, nil)
 	defer loc.Close()
 
-	si, err := jrpc2.RPCServerInfo(context.Background(), loc.Client)
-	if err != nil {
-		t.Errorf("RPCServerInfo failed: %v", err)
+	var si jrpc2.ServerInfo
+	if err := loc.Client.CallResult(context.Background(), "rpc.serverInfo", nil, &si); err != nil {
+		t.Errorf("rpc.serverInfo call failed: %v", err)
 	}
 	{
 		got, want := si.Methods, []string{"Test"}

server.go

@@ -19,6 +19,10 @@ import (
 	"golang.org/x/sync/semaphore"
 )
 
+const (
+	rpcServerInfo = "rpc.serverInfo"
+)
+
 var (
 	serverMetrics = new(expvar.Map)
 
@@ -714,7 +718,9 @@ func (s *Server) assign(ctx context.Context, name string) Handler {
 	if s.builtin && strings.HasPrefix(name, "rpc.") {
 		switch name {
 		case rpcServerInfo:
-			return methodFunc(s.handleRPCServerInfo)
+			return func(context.Context, *Request) (any, error) {
+				return s.ServerInfo(), nil
+			}
 		default:
 			return nil // reserved
 		}
@@ -827,3 +833,13 @@ func (ts tasks) numToDo() (todo, notes int) {
 	}
 	return
 }
+
+// CancelRequest instructs s to cancel the pending or in-flight request with
+// the specified ID. If no request exists with that ID, this is a no-op.
+func (s *Server) CancelRequest(id string) {
+	s.mu.Lock()
+	defer s.mu.Unlock()
+	if s.cancel(id) {
+		s.log("Cancelled request %s by client order", id)
+	}
+}

server/local_test.go

@@ -31,8 +31,8 @@ func TestLocal(t *testing.T) {
 
 	loc := server.NewLocal(make(handler.Map), testOpts(t))
 	ctx := context.Background()
-	si, err := jrpc2.RPCServerInfo(ctx, loc.Client)
-	if err != nil {
+	var si jrpc2.ServerInfo
+	if err := loc.Client.CallResult(ctx, "rpc.serverInfo", nil, &si); err != nil {
 		t.Fatalf("rpc.serverInfo failed: %v", err)
 	}