rpc: Fix json rpc to handle array and object request params.

rpc/v2/json2 code has a bug where it treats all jsonrpc 2.0
request params like an 'object'. In accordance with the spec
it could be both 'object' or an 'array'.

Handle both cases.

vendor/github.com/gorilla/rpc/v2/json2/json_test.go

@@ -71,7 +71,7 @@ type Service1Request struct {
 	B int
 }
 
-type Service1BadRequest struct {
+type Service1NoParamsRequest struct {
 	V  string `json:"jsonrpc"`
 	M  string `json:"method"`
 	ID uint64 `json:"id"`
@@ -84,8 +84,15 @@ type Service1Response struct {
 type Service1 struct {
 }
 
+const Service1DefaultResponse = 9999
+
 func (t *Service1) Multiply(r *http.Request, req *Service1Request, res *Service1Response) error {
+	if req.A == 0 && req.B == 0 {
+		// Sentinel value for test with no params.
+		res.Result = Service1DefaultResponse
+	} else {
 		res.Result = req.A * req.B
+	}
 	return nil
 }
 
@@ -139,8 +146,13 @@ func TestService(t *testing.T) {
 		t.Errorf("Expected to get %q, but got %q", ErrResponseError, err)
 	}
 
-	if err := executeRaw(t, s, &Service1BadRequest{"2.0", "Service1.Multiply", 1}, &res); err == nil {
-		t.Errorf("Expected error but error in nil")
+	// No parameters.
+	res = Service1Response{}
+	if err := executeRaw(t, s, &Service1NoParamsRequest{"2.0", "Service1.Multiply", 1}, &res); err != nil {
+		t.Error(err)
+	}
+	if res.Result != Service1DefaultResponse {
+		t.Errorf("Wrong response: got %v, want %v", res.Result, Service1DefaultResponse)
 	}
 }
 

vendor/github.com/gorilla/rpc/v2/json2/server.go

@@ -125,22 +125,21 @@ func (c *CodecRequest) Method() (string, error) {
 
 // ReadRe<quest fills the request object for the RPC method.
 func (c *CodecRequest) ReadRequest(args interface{}) error {
-	if c.err == nil {
-		if c.request.Params != nil {
+	if c.err == nil && c.request.Params != nil {
+		// Note: if c.request.Params is nil it's not an error, it's an optional member.
 		// JSON params structured object. Unmarshal to the args object.
-			err := json.Unmarshal(*c.request.Params, args)
-			if err != nil {
+		if err := json.Unmarshal(*c.request.Params, args); err != nil {
+			// Structed unmarshalling failed, attempt JSON params as
+			// array value. Unmarshal into array containing the
+			// request struct.
+			params := [1]interface{}{args}
+			if err = json.Unmarshal(*c.request.Params, &params); err != nil {
 				c.err = &Error{
 					Code:    E_INVALID_REQ,
 					Message: err.Error(),
 					Data:    c.request.Params,
 				}
 			}
-		} else {
-			c.err = &Error{
-				Code:    E_INVALID_REQ,
-				Message: "rpc: method request ill-formed: missing params field",
-			}
 		}
 	}
 	return c.err

vendor/vendor.json

@@ -44,8 +44,8 @@
 		},
 		{
 			"path": "github.com/gorilla/rpc/v2/json2",
-			"revision": "839c4c31c6bb12c15f41802cf89325aa89439ac3",
-			"revisionTime": "2015-07-14T15:53:15-07:00"
+			"revision": "64e20900b8aa38bb0771dec71ba3bcc2b07fc8ec",
+			"revisionTime": "2015-11-05T07:45:51+08:00"
 		},
 		{
 			"path": "github.com/mattn/go-isatty",