RPC request can omit params if the handler's only argument is a conte…

…xt (#1265)

jsonrpc/server.go

@@ -372,6 +372,17 @@ func (s *Server) handleRequest(ctx context.Context, req *request) (*response, er
 }
 
 func (s *Server) buildArguments(ctx context.Context, params any, method Method) ([]reflect.Value, error) {
+	handlerType := reflect.TypeOf(method.Handler)
+
+	numArgs := handlerType.NumIn()
+	args := make([]reflect.Value, 0, numArgs)
+	addContext := 0
+
+	if method.needsContext {
+		args = append(args, reflect.ValueOf(ctx))
+		addContext = 1
+	}
+
 	if isNil(params) {
 		allParamsAreOptional := utils.All(method.Params, func(p Parameter) bool {
 			return p.Optional
@@ -381,18 +392,12 @@ func (s *Server) buildArguments(ctx context.Context, params any, method Method)
 			return nil, errors.New("missing non-optional param field")
 		}
 
-		return s.buildDefaultArguments(ctx, method)
-	}
-
-	handlerType := reflect.TypeOf(method.Handler)
-
-	numArgs := handlerType.NumIn()
-	args := make([]reflect.Value, 0, numArgs)
-	addContext := 0
+		for i := addContext; i < numArgs; i++ {
+			arg := reflect.New(handlerType.In(i)).Elem()
+			args = append(args, arg)
+		}
 
-	if method.needsContext {
-		args = append(args, reflect.ValueOf(ctx))
-		addContext = 1
+		return args, nil
 	}
 
 	switch reflect.TypeOf(params).Kind() {
@@ -437,20 +442,6 @@ func (s *Server) buildArguments(ctx context.Context, params any, method Method)
 	return args, nil
 }
 
-func (s *Server) buildDefaultArguments(_ context.Context, method Method) ([]reflect.Value, error) {
-	handlerType := reflect.TypeOf(method.Handler)
-
-	numArgs := handlerType.NumIn()
-	args := make([]reflect.Value, 0, numArgs)
-
-	for i := 0; i < numArgs; i++ {
-		arg := reflect.New(handlerType.In(i)).Elem()
-		args = append(args, arg)
-	}
-
-	return args, nil
-}
-
 func (s *Server) parseParam(param any, t reflect.Type) (reflect.Value, error) {
 	handlerParam := reflect.New(t)
 	valueMarshaled, err := json.Marshal(param) // we have to marshal the value into JSON again

jsonrpc/server_test.go

@@ -138,13 +138,17 @@ func TestHandle(t *testing.T) {
 			},
 		},
 		{
-			Name:    "acceptsContext",
-			Handler: func(_ context.Context) (int, *jsonrpc.Error) { return 0, nil },
+			Name: "acceptsContext",
+			Handler: func(ctx context.Context) (int, *jsonrpc.Error) {
+				require.NotNil(t, ctx)
+				return 0, nil
+			},
 		},
 		{
 			Name:   "acceptsContextAndTwoParams",
 			Params: []jsonrpc.Parameter{{Name: "a"}, {Name: "b"}},
-			Handler: func(_ context.Context, a, b int) (int, *jsonrpc.Error) {
+			Handler: func(ctx context.Context, a, b int) (int, *jsonrpc.Error) {
+				require.NotNil(t, ctx)
 				return b - a, nil
 			},
 		},
@@ -381,6 +385,10 @@ func TestHandle(t *testing.T) {
 			req: `{"jsonrpc": "2.0", "method": "acceptsContext", "params": [], "id": 1}`,
 			res: `{"jsonrpc":"2.0","result":0,"id":1}`,
 		},
+		"handler accepts context without params": {
+			req: `{"jsonrpc": "2.0", "method": "acceptsContext","id": 1}`,
+			res: `{"jsonrpc":"2.0","result":0,"id":1}`,
+		},
 		"handler accepts context and two params with array params": {
 			req: `{"jsonrpc": "2.0", "method": "acceptsContextAndTwoParams", "params": [1, 3], "id": 1}`,
 			res: `{"jsonrpc":"2.0","result":2,"id":1}`,