Introduce custom extensions for JSON-RPC 2.0 Response

handlers_test.go

@@ -2,6 +2,8 @@ package zenrpc_test
 
 import (
 	"bytes"
+	"context"
+	"encoding/json"
 	"io/ioutil"
 	"log"
 	"net/http"
@@ -309,6 +311,71 @@ func TestServer_ServeHTTPWithErrors(t *testing.T) {
 	}
 }
 
+func TestServer_Extensions(t *testing.T) {
+	middleware := func(h zenrpc.InvokeFunc) zenrpc.InvokeFunc {
+		return func(ctx context.Context, method string, params json.RawMessage) zenrpc.Response {
+			r := h(ctx, method, params)
+
+			// ignore multiply method
+			if method != testdata.RPC.ArithService.Multiply {
+				r.Extensions = map[string]interface{}{"debug": "true"}
+			}
+
+			return r
+		}
+	}
+
+	server := zenrpc.NewServer(zenrpc.Options{AllowCORS: true, HideErrorDataField: true})
+	server.Register("arith", &testdata.ArithService{})
+	server.Use(middleware)
+
+	ts := httptest.NewServer(http.HandlerFunc(server.ServeHTTP))
+	defer ts.Close()
+
+	var tc = []struct {
+		url     string
+		in, out string
+	}{
+		{
+			url: ts.URL,
+			in:  `{"jsonrpc": "2.0", "method": "multiple1", "id": 1 }`,
+			out: `{"jsonrpc":"2.0","id":1,"error":{"code":-32601,"message":"Method not found"}}`},
+		{
+			url: ts.URL,
+			in:  `{"jsonrpc": "2.0", "method": "arith.divide", "params": { "a": 1, "b": 24 }}`,
+			out: ``},
+		{
+			url: ts.URL,
+			in:  `{"jsonrpc": "2.0", "method": "arith.divide", "params": { "a": 1, "b": 24 }, "id": 1 }`,
+			out: `{"jsonrpc":"2.0","id":1,"result":{"Quo":0,"rem":1},"extensions":{"debug":"true"}}`},
+		{
+			url: ts.URL,
+			in:  `{"jsonrpc": "2.0", "method": "arith.multiply", "params": { "a": 1, "b": 24 }, "id": 1 }`,
+			out: `{"jsonrpc":"2.0","id":1,"result":24}`},
+		{
+			url: ts.URL,
+			in:  `{"jsonrpc": "2.0", "method": "arith.checkerror", "params": [ true ], "id": 1 }`,
+			out: `{"jsonrpc":"2.0","id":1,"error":{"code":-32603,"message":"test"},"extensions":{"debug":"true"}}`},
+	}
+
+	for _, c := range tc {
+		res, err := http.Post(c.url, "application/json", bytes.NewBufferString(c.in))
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		resp, err := ioutil.ReadAll(res.Body)
+		res.Body.Close()
+		if err != nil {
+			log.Fatal(err)
+		}
+
+		if string(resp) != c.out {
+			t.Errorf("Input: %s\n got %s expected %s", c.in, resp, c.out)
+		}
+	}
+}
+
 func TestServer_ServeWS(t *testing.T) {
 	ts := httptest.NewServer(http.HandlerFunc(rpc.ServeWS))
 	defer ts.Close()

jsonrpc2.go

@@ -94,6 +94,9 @@ type Response struct {
 	// This member MUST NOT exist if there was no error triggered during invocation.
 	// The value for this member MUST be an Object as defined in section 5.1.
 	Error *Error `json:"error,omitempty"`
+
+	// Extensions is additional field for extending standard response. It could be useful for tracing, method execution, etc...
+	Extensions map[string]interface{} `json:"extensions,omitempty"`
 }
 
 // JSON is temporary method that silences error during json marshalling.
@@ -120,6 +123,7 @@ type Error struct {
 	// The value of this member is defined by the Server (e.g. detailed error information, nested errors etc.).
 	Data interface{} `json:"data,omitempty"`
 
+	// Err is inner error.
 	Err error `json:"-"`
 }