Add IsCloseError, improve doc about errors

conn.go

@@ -102,6 +102,19 @@ func (e *CloseError) Error() string {
 	return "websocket: close " + strconv.Itoa(e.Code) + " " + e.Text
 }
 
+// IsCloseError returns boolean indicating whether the error is a *CloseError
+// with one of the specified codes.
+func IsCloseError(err error, codes ...int) bool {
+	if e, ok := err.(*CloseError); ok {
+		for _, code := range codes {
+			if e.Code == code {
+				return true
+			}
+		}
+	}
+	return false
+}
+
 var (
 	errWriteTimeout        = &netError{msg: "websocket: write timeout", timeout: true, temporary: true}
 	errUnexpectedEOF       = &CloseError{Code: CloseAbnormalClosure, Text: io.ErrUnexpectedEOF.Error()}
@@ -694,8 +707,8 @@ func (c *Conn) handleProtocolError(message string) error {
 // There can be at most one open reader on a connection. NextReader discards
 // the previous message if the application has not already consumed it.
 //
-// The NextReader method and the readers returned from the method cannot be
+// Errors returned from NextReader are permanent. If NextReader returns a
-// accessed by more than one goroutine at a time.
+// non-nil error, then all subsequent calls to NextReader will the same error.
 func (c *Conn) NextReader() (messageType int, r io.Reader, err error) {
 
 	c.readSeq++

conn_test.go

@@ -7,6 +7,7 @@ package websocket
 import (
 	"bufio"
 	"bytes"
+	"errors"
 	"fmt"
 	"io"
 	"io/ioutil"
@@ -270,3 +271,23 @@ func TestBufioReadBytes(t *testing.T) {
 		t.Fatalf("read returnd %d bytes, want %d bytes", len(p), len(m))
 	}
 }
+
+var closeErrorTests = []struct {
+	err   error
+	codes []int
+	ok    bool
+}{
+	{&CloseError{Code: CloseNormalClosure}, []int{CloseNormalClosure}, true},
+	{&CloseError{Code: CloseNormalClosure}, []int{CloseNoStatusReceived}, false},
+	{&CloseError{Code: CloseNormalClosure}, []int{CloseNoStatusReceived, CloseNormalClosure}, true},
+	{errors.New("hello"), []int{CloseNormalClosure}, false},
+}
+
+func TestCloseError(t *testing.T) {
+	for _, tt := range closeErrorTests {
+		ok := IsCloseError(tt.err, tt.codes...)
+		if ok != tt.ok {
+			t.Errorf("IsCloseError(%#v, %#v) returned %v, want %v", tt.err, tt.codes, ok, tt.ok)
+		}
+	}
+}