WebUI: move from rpc/v2/json to rpc/v2/json2 which has better error response structure.

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

@@ -0,0 +1,190 @@
+// Copyright 2009 The Go Authors. All rights reserved.
+// Copyright 2012 The Gorilla Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+package json2
+
+import (
+	"encoding/json"
+	"net/http"
+
+	"github.com/gorilla/rpc/v2"
+)
+
+var null = json.RawMessage([]byte("null"))
+var Version = "2.0"
+
+// ----------------------------------------------------------------------------
+// Request and Response
+// ----------------------------------------------------------------------------
+
+// serverRequest represents a JSON-RPC request received by the server.
+type serverRequest struct {
+	// JSON-RPC protocol.
+	Version string `json:"jsonrpc"`
+
+	// A String containing the name of the method to be invoked.
+	Method string `json:"method"`
+
+	// A Structured value to pass as arguments to the method.
+	Params *json.RawMessage `json:"params"`
+
+	// The request id. MUST be a string, number or null.
+	// Our implementation will not do type checking for id.
+	// It will be copied as it is.
+	Id *json.RawMessage `json:"id"`
+}
+
+// serverResponse represents a JSON-RPC response returned by the server.
+type serverResponse struct {
+	// JSON-RPC protocol.
+	Version string `json:"jsonrpc"`
+
+	// The Object that was returned by the invoked method. This must be null
+	// in case there was an error invoking the method.
+	// As per spec the member will be omitted if there was an error.
+	Result interface{} `json:"result,omitempty"`
+
+	// An Error object if there was an error invoking the method. It must be
+	// null if there was no error.
+	// As per spec the member will be omitted if there was no error.
+	Error *Error `json:"error,omitempty"`
+
+	// This must be the same id as the request it is responding to.
+	Id *json.RawMessage `json:"id"`
+}
+
+// ----------------------------------------------------------------------------
+// Codec
+// ----------------------------------------------------------------------------
+
+// NewcustomCodec returns a new JSON Codec based on passed encoder selector.
+func NewCustomCodec(encSel rpc.EncoderSelector) *Codec {
+	return &Codec{encSel: encSel}
+}
+
+// NewCodec returns a new JSON Codec.
+func NewCodec() *Codec {
+	return NewCustomCodec(rpc.DefaultEncoderSelector)
+}
+
+// Codec creates a CodecRequest to process each request.
+type Codec struct {
+	encSel rpc.EncoderSelector
+}
+
+// NewRequest returns a CodecRequest.
+func (c *Codec) NewRequest(r *http.Request) rpc.CodecRequest {
+	return newCodecRequest(r, c.encSel.Select(r))
+}
+
+// ----------------------------------------------------------------------------
+// CodecRequest
+// ----------------------------------------------------------------------------
+
+// newCodecRequest returns a new CodecRequest.
+func newCodecRequest(r *http.Request, encoder rpc.Encoder) rpc.CodecRequest {
+	// Decode the request body and check if RPC method is valid.
+	req := new(serverRequest)
+	err := json.NewDecoder(r.Body).Decode(req)
+	if err != nil {
+		err = &Error{
+			Code:    E_PARSE,
+			Message: err.Error(),
+			Data:    req,
+		}
+	}
+	if req.Version != Version {
+		err = &Error{
+			Code:    E_INVALID_REQ,
+			Message: "jsonrpc must be " + Version,
+			Data:    req,
+		}
+	}
+	r.Body.Close()
+	return &CodecRequest{request: req, err: err, encoder: encoder}
+}
+
+// CodecRequest decodes and encodes a single request.
+type CodecRequest struct {
+	request *serverRequest
+	err     error
+	encoder rpc.Encoder
+}
+
+// Method returns the RPC method for the current request.
+//
+// The method uses a dotted notation as in "Service.Method".
+func (c *CodecRequest) Method() (string, error) {
+	if c.err == nil {
+		return c.request.Method, nil
+	}
+	return "", c.err
+}
+
+// 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 {
+			// JSON params structured object. Unmarshal to the args object.
+			err := json.Unmarshal(*c.request.Params, args)
+			if 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
+}
+
+// WriteResponse encodes the response and writes it to the ResponseWriter.
+func (c *CodecRequest) WriteResponse(w http.ResponseWriter, reply interface{}) {
+	res := &serverResponse{
+		Version: Version,
+		Result:  reply,
+		Id:      c.request.Id,
+	}
+	c.writeServerResponse(w, res)
+}
+
+func (c *CodecRequest) WriteError(w http.ResponseWriter, status int, err error) {
+	jsonErr, ok := err.(*Error)
+	if !ok {
+		jsonErr = &Error{
+			Code:    E_SERVER,
+			Message: err.Error(),
+		}
+	}
+	res := &serverResponse{
+		Version: Version,
+		Error:   jsonErr,
+		Id:      c.request.Id,
+	}
+	c.writeServerResponse(w, res)
+}
+
+func (c *CodecRequest) writeServerResponse(w http.ResponseWriter, res *serverResponse) {
+	// Id is null for notifications and they don't have a response.
+	if c.request.Id != nil {
+		w.Header().Set("Content-Type", "application/json; charset=utf-8")
+		encoder := json.NewEncoder(c.encoder.Encode(w))
+		err := encoder.Encode(res)
+
+		// Not sure in which case will this happen. But seems harmless.
+		if err != nil {
+			rpc.WriteError(w, 400, err.Error())
+		}
+	}
+}
+
+type EmptyResponse struct {
+}