Add pluggable transport interface + WebSocket support

simplify API by using interface{}, rename from transport -> stream

add WebSocket transport in websocket subpackage

do not buffer in ReadObject, rename GetObjectReader/ReadObject -> NextObjectReader

use xtest (jsonrpc2_test) package to allow us to test subpackages that depend on us (in a future change)

factor out vscode-specific transport code and allow pluggable transports

remove Server (unused) and Serve (unnecessary):
  The Serve func had nothing specific to JSON-RPC; it was just a loop
  around (net.Listener).Accept. It added no value.

codec_test.go

@@ -0,0 +1,34 @@
+package jsonrpc2
+
+import (
+	"bufio"
+	"bytes"
+	"strings"
+	"testing"
+)
+
+func TestVarintObjectCodec(t *testing.T) {
+	want := 789
+	var buf bytes.Buffer
+	if err := (VarintObjectCodec{}).WriteObject(&buf, want); err != nil {
+		t.Fatal(err)
+	}
+	var v int
+	if err := (VarintObjectCodec{}).ReadObject(bufio.NewReader(&buf), &v); err != nil {
+		t.Fatal(err)
+	}
+	if want := want; v != want {
+		t.Errorf("got %v, want %v", v, want)
+	}
+}
+
+func TestVSCodeObjectCodec_ReadObject(t *testing.T) {
+	s := "Content-Type: foo\r\nContent-Length: 123\r\n\r\n789"
+	var v int
+	if err := (VSCodeObjectCodec{}).ReadObject(bufio.NewReader(strings.NewReader(s)), &v); err != nil {
+		t.Fatal(err)
+	}
+	if want := 789; v != want {
+		t.Errorf("got %v, want %v", v, want)
+	}
+}

jsonrpc2.go

@@ -3,16 +3,13 @@
 package jsonrpc2
 
 import (
-	"bufio"
 	"context"
 	"encoding/json"
 	"errors"
 	"fmt"
 	"io"
 	"log"
-	"net"
 	"strconv"
-	"strings"
 	"sync"
 )
 
@@ -243,8 +240,7 @@ func (id *ID) UnmarshalJSON(data []byte) error {
 // is symmetric, so a Conn runs on both ends of a client-server
 // connection.
 type Conn struct {
-	conn io.Closer // all writes should go through w, all reads through readMessages
+	stream ObjectStream
-	w    *bufio.Writer
 
 	h Handler
 
@@ -276,10 +272,9 @@ var ErrClosed = errors.New("jsonrpc2: connection is closed")
 //
 // NewClient consumes conn, so you should call Close on the returned
 // client not on the given conn.
-func NewConn(ctx context.Context, conn io.ReadWriteCloser, h Handler, opt ...ConnOpt) *Conn {
+func NewConn(ctx context.Context, stream ObjectStream, h Handler, opt ...ConnOpt) *Conn {
 	c := &Conn{
-		conn:       conn,
+		stream:     stream,
-		w:          bufio.NewWriter(conn),
 		h:          h,
 		pending:    map[ID]*call{},
 		disconnect: make(chan struct{}),
@@ -287,7 +282,7 @@ func NewConn(ctx context.Context, conn io.ReadWriteCloser, h Handler, opt ...Con
 	for _, opt := range opt {
 		opt(c)
 	}
-	go c.readMessages(ctx, bufio.NewReader(conn))
+	go c.readMessages(ctx)
 	return c
 }
 
@@ -301,10 +296,10 @@ func (c *Conn) Close() error {
 	}
 	c.closing = true
 	c.mu.Unlock()
-	return c.conn.Close()
+	return c.stream.Close()
 }
 
-func (c *Conn) send(ctx context.Context, m *anyMessage, wait bool) (*call, error) {
+func (c *Conn) send(ctx context.Context, m *anyMessage, wait bool) (cc *call, err error) {
 	c.sending.Lock()
 	defer c.sending.Unlock()
 
@@ -316,7 +311,6 @@ func (c *Conn) send(ctx context.Context, m *anyMessage, wait bool) (*call, error
 
 	// Store requests so we can later associate them with incoming
 	// responses.
-	var cc *call
 	if m.request != nil && wait {
 		cc = &call{request: m.request, seq: c.seq, done: make(chan error, 1)}
 		c.pending[ID{Num: c.seq}] = cc // use next seq as call ID
@@ -334,17 +328,23 @@ func (c *Conn) send(ctx context.Context, m *anyMessage, wait bool) (*call, error
 		}
 	}
 
-	err := marshalHeadersAndBody(c.w, m)
+	// From here on, if we fail to send this, then we need to remove
+	// this from the pending map so we don't block on it or pile up
+	// pending entries for unsent messages.
+	defer func() {
 		if err != nil {
-		c.w.Flush()
 			if cc != nil {
 				c.mu.Lock()
 				delete(c.pending, ID{Num: cc.seq})
 				c.mu.Unlock()
 			}
+		}
+	}()
+
+	if err := c.stream.WriteObject(m); err != nil {
 		return nil, err
 	}
-	return cc, c.w.Flush()
+	return cc, nil
 }
 
 // Call initiates a JSON-RPC call using the specified method and
@@ -431,16 +431,11 @@ func (c *Conn) DisconnectNotify() <-chan struct{} {
 	return c.disconnect
 }
 
-func (c *Conn) readMessages(ctx context.Context, r *bufio.Reader) {
+func (c *Conn) readMessages(ctx context.Context) {
 	var err error
 	for err == nil {
 		var m anyMessage
-
+		err = c.stream.ReadObject(&m)
-		var n uint32
-		n, err = readHeaderContentLength(r)
-		if err == nil {
-			err = json.NewDecoder(io.LimitReader(r, int64(n))).Decode(&m)
-		}
 		if err != nil {
 			break
 		}
@@ -513,20 +508,6 @@ func (c *Conn) readMessages(ctx context.Context, r *bufio.Reader) {
 	close(c.disconnect)
 }
 
-// Server is a JSON-RPC server.
-type Server struct{}
-
-// Serve starts a new JSON-RPC server.
-func Serve(ctx context.Context, lis net.Listener, h Handler, opt ...ConnOpt) error {
-	for {
-		conn, err := lis.Accept()
-		if err != nil {
-			return err
-		}
-		NewConn(ctx, conn, h, opt...)
-	}
-}
-
 // call represents a JSON-RPC call over its entire lifecycle.
 type call struct {
 	request  *Request
@@ -612,49 +593,6 @@ func (m *anyMessage) UnmarshalJSON(data []byte) error {
 	return json.Unmarshal(data, v)
 }
 
-func readHeaderContentLength(r *bufio.Reader) (contentLength uint32, err error) {
-	for {
-		line, err := r.ReadString('\r')
-		if err != nil {
-			return 0, err
-		}
-		b, err := r.ReadByte()
-		if err != nil {
-			return 0, err
-		}
-		if b != '\n' {
-			return 0, fmt.Errorf(`jsonrpc2: line endings must be \r\n`)
-		}
-		if line == "\r" {
-			break
-		}
-		if strings.HasPrefix(line, "Content-Length: ") {
-			line = strings.TrimPrefix(line, "Content-Length: ")
-			line = strings.TrimSpace(line)
-			n, err := strconv.ParseUint(line, 10, 32)
-			if err != nil {
-				return 0, err
-			}
-			contentLength = uint32(n)
-		}
-	}
-	if contentLength == 0 {
-		err = fmt.Errorf("jsonrpc2: no Content-Length header found")
-	}
-	return
-}
-
-func marshalHeadersAndBody(w io.Writer, v interface{}) error {
-	body, err := json.Marshal(v)
-	if err != nil {
-		return err
-	}
-	fmt.Fprintf(w, "Content-Length: %d\r\n", len(body))
-	fmt.Fprint(w, "Content-Type: application/vscode-jsonrpc; charset=utf8\r\n\r\n")
-	_, err = w.Write(body)
-	return err
-}
-
 var (
 	errInvalidRequestJSON  = errors.New("jsonrpc2: request must be either a JSON object or JSON array")
 	errInvalidResponseJSON = errors.New("jsonrpc2: response must be either a JSON object or JSON array")

jsonrpc2_test.go

@@ -1,22 +1,26 @@
-package jsonrpc2
+package jsonrpc2_test
 
 import (
-	"bufio"
 	"bytes"
 	"context"
 	"encoding/json"
 	"fmt"
 	"io"
 	"net"
-	"reflect"
+	"net/http"
+	"net/http/httptest"
 	"strings"
 	"sync"
 	"testing"
 	"time"
+
+	"github.com/gorilla/websocket"
+	"github.com/sourcegraph/jsonrpc2"
+	websocketjsonrpc2 "github.com/sourcegraph/jsonrpc2/websocket"
 )
 
 func TestRequest_MarshalJSON_jsonrpc(t *testing.T) {
-	b, err := json.Marshal(&Request{})
+	b, err := json.Marshal(&jsonrpc2.Request{})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -26,7 +30,7 @@ func TestRequest_MarshalJSON_jsonrpc(t *testing.T) {
 }
 
 func TestResponse_MarshalJSON_jsonrpc(t *testing.T) {
-	b, err := json.Marshal(&Response{})
+	b, err := json.Marshal(&jsonrpc2.Response{})
 	if err != nil {
 		t.Fatal(err)
 	}
@@ -36,12 +40,12 @@ func TestResponse_MarshalJSON_jsonrpc(t *testing.T) {
 }
 
 func TestResponseMarshalJSON_Notif(t *testing.T) {
-	tests := map[*Request]bool{
+	tests := map[*jsonrpc2.Request]bool{
-		&Request{ID: ID{Num: 0}}:                   true,
+		&jsonrpc2.Request{ID: jsonrpc2.ID{Num: 0}}:                   true,
-		&Request{ID: ID{Num: 1}}:                   true,
+		&jsonrpc2.Request{ID: jsonrpc2.ID{Num: 1}}:                   true,
-		&Request{ID: ID{Str: "", IsString: true}}:  true,
+		&jsonrpc2.Request{ID: jsonrpc2.ID{Str: "", IsString: true}}:  true,
-		&Request{ID: ID{Str: "a", IsString: true}}: true,
+		&jsonrpc2.Request{ID: jsonrpc2.ID{Str: "a", IsString: true}}: true,
-		&Request{Notif: true}:                      false,
+		&jsonrpc2.Request{Notif: true}:                               false,
 	}
 	for r, wantIDKey := range tests {
 		b, err := json.Marshal(r)
@@ -64,7 +68,7 @@ func TestResponseUnmarshalJSON_Notif(t *testing.T) {
 		`{"method":"f"}`:          true,
 	}
 	for s, want := range tests {
-		var r Request
+		var r jsonrpc2.Request
 		if err := json.Unmarshal([]byte(s), &r); err != nil {
 			t.Fatal(err)
 		}
@@ -77,7 +81,7 @@ func TestResponseUnmarshalJSON_Notif(t *testing.T) {
 // testHandlerA is the "server" handler.
 type testHandlerA struct{ t *testing.T }
 
-func (h *testHandlerA) Handle(ctx context.Context, conn *Conn, req *Request) {
+func (h *testHandlerA) Handle(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request) {
 	if req.Notif {
 		return // notification
 	}
@@ -97,7 +101,7 @@ type testHandlerB struct {
 	got []string
 }
 
-func (h *testHandlerB) Handle(ctx context.Context, conn *Conn, req *Request) {
+func (h *testHandlerB) Handle(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request) {
 	if req.Notif {
 		h.mu.Lock()
 		defer h.mu.Unlock()
@@ -108,8 +112,10 @@ func (h *testHandlerB) Handle(ctx context.Context, conn *Conn, req *Request) {
 }
 
 func TestClientServer(t *testing.T) {
+	t.Run("tcp", func(t *testing.T) {
 		ctx := context.Background()
 		done := make(chan struct{})
+
 		lis, err := net.Listen("tcp", "127.0.0.1:0") // any available address
 		if err != nil {
 			t.Fatal("Listen:", err)
@@ -127,7 +133,7 @@ func TestClientServer(t *testing.T) {
 
 		ha := testHandlerA{t: t}
 		go func() {
-		if err := Serve(ctx, lis, &ha); err != nil {
+			if err := serve(ctx, lis, &ha); err != nil {
 				if !strings.HasSuffix(err.Error(), "use of closed network connection") {
 					t.Error(err)
 				}
@@ -139,8 +145,43 @@ func TestClientServer(t *testing.T) {
 		if err != nil {
 			t.Fatal("Dial:", err)
 		}
+		testClientServer(ctx, t, jsonrpc2.NewBufferedStream(conn, jsonrpc2.VarintObjectCodec{}))
+
+		lis.Close()
+		<-done // ensure Serve's error return (if any) is caught by this test
+	})
+	t.Run("websocket", func(t *testing.T) {
+		ctx := context.Background()
+		done := make(chan struct{})
+
+		ha := testHandlerA{t: t}
+		upgrader := websocket.Upgrader{ReadBufferSize: 1024, WriteBufferSize: 1024}
+		s := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			c, err := upgrader.Upgrade(w, r, nil)
+			if err != nil {
+				t.Fatal(err)
+			}
+			defer c.Close()
+			jc := jsonrpc2.NewConn(r.Context(), websocketjsonrpc2.NewObjectStream(c), &ha)
+			<-jc.DisconnectNotify()
+			close(done)
+		}))
+		defer s.Close()
+
+		c, _, err := websocket.DefaultDialer.Dial(strings.Replace(s.URL, "http:", "ws:", 1), nil)
+		if err != nil {
+			t.Fatal(err)
+		}
+		defer c.Close()
+		testClientServer(ctx, t, websocketjsonrpc2.NewObjectStream(c))
+
+		<-done // keep the test running until the WebSocket disconnects (to avoid missing errors)
+	})
+}
+
+func testClientServer(ctx context.Context, t *testing.T, stream jsonrpc2.ObjectStream) {
 	hb := testHandlerB{t: t}
-	cc := NewConn(ctx, conn, &hb)
+	cc := jsonrpc2.NewConn(ctx, stream, &hb)
 	defer func() {
 		if err := cc.Close(); err != nil {
 			t.Fatal(err)
@@ -164,14 +205,11 @@ func TestClientServer(t *testing.T) {
 		t.Errorf("testHandlerB got %d notifications, want %d", len(hb.got), n)
 	}
 	hb.mu.Unlock()
-
-	lis.Close()
-	<-done // ensure Serve's error return (if any) is caught by this test
 }
 
 type noopHandler struct{}
 
-func (noopHandler) Handle(ctx context.Context, conn *Conn, req *Request) {}
+func (noopHandler) Handle(ctx context.Context, conn *jsonrpc2.Conn, req *jsonrpc2.Request) {}
 
 type readWriteCloser struct {
 	read, write func(p []byte) (n int, err error)
@@ -192,7 +230,7 @@ func eof(p []byte) (n int, err error) {
 }
 
 func TestConn_DisconnectNotify_EOF(t *testing.T) {
-	c := NewConn(context.Background(), &readWriteCloser{eof, eof}, nil)
+	c := jsonrpc2.NewConn(context.Background(), jsonrpc2.NewBufferedStream(&readWriteCloser{eof, eof}, jsonrpc2.VarintObjectCodec{}), nil)
 	select {
 	case <-c.DisconnectNotify():
 	case <-time.After(200 * time.Millisecond):
@@ -201,7 +239,7 @@ func TestConn_DisconnectNotify_EOF(t *testing.T) {
 }
 
 func TestConn_DisconnectNotify_Close(t *testing.T) {
-	c := NewConn(context.Background(), &readWriteCloser{eof, eof}, nil)
+	c := jsonrpc2.NewConn(context.Background(), jsonrpc2.NewBufferedStream(&readWriteCloser{eof, eof}, jsonrpc2.VarintObjectCodec{}), nil)
 	if err := c.Close(); err != nil {
 		t.Error(err)
 	}
@@ -214,9 +252,9 @@ func TestConn_DisconnectNotify_Close(t *testing.T) {
 
 func TestConn_DisconnectNotify_Close_async(t *testing.T) {
 	done := make(chan struct{})
-	c := NewConn(context.Background(), &readWriteCloser{eof, eof}, nil)
+	c := jsonrpc2.NewConn(context.Background(), jsonrpc2.NewBufferedStream(&readWriteCloser{eof, eof}, jsonrpc2.VarintObjectCodec{}), nil)
 	go func() {
-		if err := c.Close(); err != nil && err != ErrClosed {
+		if err := c.Close(); err != nil && err != jsonrpc2.ErrClosed {
 			t.Error(err)
 		}
 		close(done)
@@ -230,15 +268,15 @@ func TestConn_DisconnectNotify_Close_async(t *testing.T) {
 }
 
 func TestConn_Close_waitingForResponse(t *testing.T) {
-	c := NewConn(context.Background(), &readWriteCloser{eof, eof}, noopHandler{})
+	c := jsonrpc2.NewConn(context.Background(), jsonrpc2.NewBufferedStream(&readWriteCloser{eof, eof}, jsonrpc2.VarintObjectCodec{}), noopHandler{})
 	done := make(chan struct{})
 	go func() {
-		if err := c.Call(context.Background(), "m", nil, nil); err != ErrClosed {
+		if err := c.Call(context.Background(), "m", nil, nil); err != jsonrpc2.ErrClosed {
-			t.Errorf("got error %v, want %v", err, ErrClosed)
+			t.Errorf("got error %v, want %v", err, jsonrpc2.ErrClosed)
 		}
 		close(done)
 	}()
-	if err := c.Close(); err != nil && err != ErrClosed {
+	if err := c.Close(); err != nil && err != jsonrpc2.ErrClosed {
 		t.Error(err)
 	}
 	select {
@@ -249,65 +287,12 @@ func TestConn_Close_waitingForResponse(t *testing.T) {
 	<-done
 }
 
-func TestAnyMessage(t *testing.T) {
+func serve(ctx context.Context, lis net.Listener, h jsonrpc2.Handler, opt ...jsonrpc2.ConnOpt) error {
-	tests := map[string]struct {
+	for {
-		request, response bool
+		conn, err := lis.Accept()
-	}{
-		// Single messages
-		`{}`:                                   {},
-		`{"foo":"bar"}`:                        {},
-		`{"method":"m"}`:                       {request: true},
-		`{"result":123}`:                       {response: true},
-		`{"error":{"code":456,"message":"m"}}`: {response: true},
-	}
-	for s, want := range tests {
-		var m anyMessage
-		json.Unmarshal([]byte(s), &m)
-		if (m.request != nil) != want.request {
-			t.Errorf("%s: got request %v, want %v", s, m.request != nil, want.request)
-		}
-		if (m.response != nil) != want.response {
-			t.Errorf("%s: got response %v, want %v", s, m.response != nil, want.response)
-		}
-	}
-}
-
-func TestMessageCodec(t *testing.T) {
-	tests := []struct {
-		v, vempty interface{}
-	}{
-		{
-			v:      &Request{ID: ID{Num: 123}},
-			vempty: &Request{ID: ID{Num: 123}},
-		},
-		{
-			v:      &Response{ID: ID{Num: 123}},
-			vempty: &Response{ID: ID{Num: 123}},
-		},
-	}
-	for _, test := range tests {
-		b, err := json.Marshal(test.v)
 		if err != nil {
-			t.Fatal(err)
+			return err
 		}
-
+		jsonrpc2.NewConn(ctx, jsonrpc2.NewBufferedStream(conn, jsonrpc2.VarintObjectCodec{}), h, opt...)
-		if err := json.Unmarshal(b, test.vempty); err != nil {
-			t.Fatal(err)
-		}
-
-		if !reflect.DeepEqual(test.vempty, test.v) {
-			t.Errorf("got %+v, want %+v", test.vempty, test.v)
-		}
-	}
-}
-
-func TestReadHeaderContentLength(t *testing.T) {
-	s := "Content-Type: foo\r\nContent-Length: 123\r\n\r\n{}"
-	n, err := readHeaderContentLength(bufio.NewReader(strings.NewReader(s)))
-	if err != nil {
-		t.Fatal(err)
-	}
-	if want := uint32(123); n != want {
-		t.Errorf("got %d, want %d", n, want)
 	}
 }

object_test.go

@@ -0,0 +1,59 @@
+package jsonrpc2
+
+import (
+	"encoding/json"
+	"reflect"
+	"testing"
+)
+
+func TestAnyMessage(t *testing.T) {
+	tests := map[string]struct {
+		request, response bool
+	}{
+		// Single messages
+		`{}`:                                   {},
+		`{"foo":"bar"}`:                        {},
+		`{"method":"m"}`:                       {request: true},
+		`{"result":123}`:                       {response: true},
+		`{"error":{"code":456,"message":"m"}}`: {response: true},
+	}
+	for s, want := range tests {
+		var m anyMessage
+		json.Unmarshal([]byte(s), &m)
+		if (m.request != nil) != want.request {
+			t.Errorf("%s: got request %v, want %v", s, m.request != nil, want.request)
+		}
+		if (m.response != nil) != want.response {
+			t.Errorf("%s: got response %v, want %v", s, m.response != nil, want.response)
+		}
+	}
+}
+
+func TestMessageCodec(t *testing.T) {
+	tests := []struct {
+		v, vempty interface{}
+	}{
+		{
+			v:      &Request{ID: ID{Num: 123}},
+			vempty: &Request{ID: ID{Num: 123}},
+		},
+		{
+			v:      &Response{ID: ID{Num: 123}},
+			vempty: &Response{ID: ID{Num: 123}},
+		},
+	}
+	for _, test := range tests {
+		b, err := json.Marshal(test.v)
+		if err != nil {
+			t.Fatal(err)
+		}
+
+		if err := json.Unmarshal(b, test.vempty); err != nil {
+			t.Fatal(err)
+		}
+
+		if !reflect.DeepEqual(test.vempty, test.v) {
+			t.Errorf("got %+v, want %+v", test.vempty, test.v)
+		}
+	}
+}

stream.go

@@ -0,0 +1,162 @@
+package jsonrpc2
+
+import (
+	"bufio"
+	"encoding/binary"
+	"encoding/json"
+	"fmt"
+	"io"
+	"strconv"
+	"strings"
+)
+
+// An ObjectStream is a bidirectional stream of JSON-RPC 2.0 objects.
+type ObjectStream interface {
+	// WriteObject writes a JSON-RPC 2.0 object to the stream.
+	WriteObject(obj interface{}) error
+
+	// ReadObject reads the next JSON-RPC 2.0 object from the stream
+	// and stores it in the value pointed to by v.
+	ReadObject(v interface{}) error
+
+	io.Closer
+}
+
+// A bufferedObjectStream is an ObjectStream that uses a buffered
+// io.ReadWriteCloser to send and receive objects.
+type bufferedObjectStream struct {
+	conn io.Closer // all writes should go through w, all reads through r
+	w    *bufio.Writer
+	r    *bufio.Reader
+
+	codec ObjectCodec
+}
+
+// NewBufferedStream creates a buffered stream from a network
+// connection (or other similar interface). The underlying
+// objectStream is used to produce the bytes to write to the stream
+// for the JSON-RPC 2.0 objects.
+func NewBufferedStream(conn io.ReadWriteCloser, codec ObjectCodec) ObjectStream {
+	return bufferedObjectStream{
+		conn:  conn,
+		w:     bufio.NewWriter(conn),
+		r:     bufio.NewReader(conn),
+		codec: codec,
+	}
+}
+
+// WriteObject implements ObjectStream.
+func (t bufferedObjectStream) WriteObject(obj interface{}) error {
+	if err := t.codec.WriteObject(t.w, obj); err != nil {
+		return err
+	}
+	return t.w.Flush()
+}
+
+// ReadObject implements ObjectStream.
+func (t bufferedObjectStream) ReadObject(v interface{}) error {
+	return t.codec.ReadObject(t.r, v)
+}
+
+// Close implements ObjectStream.
+func (t bufferedObjectStream) Close() error {
+	return t.conn.Close()
+}
+
+// An ObjectCodec specifies how to encoed and decode a JSON-RPC 2.0
+// object in a stream.
+type ObjectCodec interface {
+	// WriteObject writes a JSON-RPC 2.0 object to the stream.
+	WriteObject(stream io.Writer, obj interface{}) error
+
+	// ReadObject reads the next JSON-RPC 2.0 object from the stream
+	// and stores it in the value pointed to by v.
+	ReadObject(stream *bufio.Reader, v interface{}) error
+}
+
+// VarintObjectCodec reads/writes JSON-RPC 2.0 objects with a varint
+// header that encodes the byte length.
+type VarintObjectCodec struct{}
+
+// WriteObject implements ObjectCodec.
+func (VarintObjectCodec) WriteObject(stream io.Writer, obj interface{}) error {
+	data, err := json.Marshal(obj)
+	if err != nil {
+		return err
+	}
+	var buf [binary.MaxVarintLen64]byte
+	b := binary.PutUvarint(buf[:], uint64(len(data)))
+	if _, err := stream.Write(buf[:b]); err != nil {
+		return err
+	}
+	if _, err := stream.Write(data); err != nil {
+		return err
+	}
+	return nil
+}
+
+// ReadObject implements ObjectCodec.
+func (VarintObjectCodec) ReadObject(stream *bufio.Reader, v interface{}) error {
+	b, err := binary.ReadUvarint(stream)
+	if err != nil {
+		return err
+	}
+	return json.NewDecoder(io.LimitReader(stream, int64(b))).Decode(v)
+}
+
+// VSCodeObjectCodec reads/writes JSON-RPC 2.0 objects with
+// Content-Length and Content-Type headers, as specified by
+// https://github.com/Microsoft/language-server-protocol/blob/master/protocol.md#base-protocol.
+type VSCodeObjectCodec struct{}
+
+// WriteObject implements ObjectCodec.
+func (VSCodeObjectCodec) WriteObject(stream io.Writer, obj interface{}) error {
+	data, err := json.Marshal(obj)
+	if err != nil {
+		return err
+	}
+	if _, err := fmt.Fprintf(stream, "Content-Length: %d\r\n", len(data)); err != nil {
+		return err
+	}
+	if _, err := fmt.Fprint(stream, "Content-Type: application/vscode-jsonrpc; charset=utf8\r\n\r\n"); err != nil {
+		return err
+	}
+	if _, err := stream.Write(data); err != nil {
+		return err
+	}
+	return nil
+}
+
+// ReadObject implements ObjectCodec.
+func (VSCodeObjectCodec) ReadObject(stream *bufio.Reader, v interface{}) error {
+	var contentLength uint64
+	for {
+		line, err := stream.ReadString('\r')
+		if err != nil {
+			return err
+		}
+		b, err := stream.ReadByte()
+		if err != nil {
+			return err
+		}
+		if b != '\n' {
+			return fmt.Errorf(`jsonrpc2: line endings must be \r\n`)
+		}
+		if line == "\r" {
+			break
+		}
+		if strings.HasPrefix(line, "Content-Length: ") {
+			line = strings.TrimPrefix(line, "Content-Length: ")
+			line = strings.TrimSpace(line)
+			var err error
+			contentLength, err = strconv.ParseUint(line, 10, 32)
+			if err != nil {
+				return err
+			}
+		}
+	}
+	if contentLength == 0 {
+		return fmt.Errorf("jsonrpc2: no Content-Length header found")
+	}
+	return json.NewDecoder(io.LimitReader(stream, int64(contentLength))).Decode(v)
+}

websocket/stream.go

@@ -0,0 +1,44 @@
+// Package websocket provides WebSocket transport support for JSON-RPC
+// 2.0.
+package websocket
+
+import (
+	"io"
+
+	"github.com/gorilla/websocket"
+)
+
+// A ObjectStream is a jsonrpc2.ObjectStream that uses a WebSocket to
+// send and receive JSON-RPC 2.0 objects.
+type ObjectStream struct {
+	conn *websocket.Conn
+}
+
+// NewObjectStream creates a new jsonrpc2.ObjectStream for sending and
+// receiving JSON-RPC 2.0 objects over a WebSocket.
+func NewObjectStream(conn *websocket.Conn) ObjectStream {
+	return ObjectStream{conn: conn}
+}
+
+// WriteObject implements jsonrpc2.ObjectStream.
+func (t ObjectStream) WriteObject(obj interface{}) error {
+	return t.conn.WriteJSON(obj)
+}
+
+// ReadObject implements jsonrpc2.ObjectStream.
+func (t ObjectStream) ReadObject(v interface{}) error {
+	err := t.conn.ReadJSON(v)
+	if e, ok := err.(*websocket.CloseError); ok {
+		if e.Code == websocket.CloseAbnormalClosure && e.Text == io.ErrUnexpectedEOF.Error() {
+			// Suppress a noisy (but harmless) log message by
+			// unwrapping this error.
+			err = io.ErrUnexpectedEOF
+		}
+	}
+	return err
+}
+
+// Close implements jsonrpc2.ObjectStream.
+func (t ObjectStream) Close() error {
+	return t.conn.Close()
+}