Root path support for ServeMux

message.go

@@ -393,6 +393,10 @@ func (m Message) PathString() string {
 
 // SetPathString sets a path by a / separated string.
 func (m *Message) SetPathString(s string) {
+	if s == "/" || s == "" {
+		m.SetPath([]string{""})
+		return
+	}
 	for s[0] == '/' {
 		s = s[1:]
 	}

servmux.go

@@ -21,6 +21,9 @@ func NewServeMux() *ServeMux { return &ServeMux{m: make(map[string]muxEntry)} }
 // Does path match pattern?
 func pathMatch(pattern, path string) bool {
 	if len(pattern) == 0 {
+		if pattern == path {
+			return true
+		}
 		// should not happen
 		return false
 	}
@@ -77,9 +80,6 @@ func (mux *ServeMux) Handle(pattern string, handler Handler) {
 		pattern = pattern[1:]
 	}
 
-	if pattern == "" {
-		panic("http: invalid pattern " + pattern)
-	}
 	if handler == nil {
 		panic("http: nil handler")
 	}

servmux_test.go

@@ -18,6 +18,10 @@ func TestPathMatching(t *testing.T) {
 		msgs["b"]++
 		return nil
 	})
+	m.HandleFunc("/", func(l *net.UDPConn, a *net.UDPAddr, m *Message) *Message {
+		msgs[""]++
+		return nil
+	})
 
 	msg := &Message{}
 	msg.SetPathString("/a")
@@ -31,21 +35,28 @@ func TestPathMatching(t *testing.T) {
 	msg.Type = NonConfirmable
 	msg.SetPathString("/c")
 	m.ServeCOAP(nil, nil, msg)
+	msg.SetPathString("/")
+	m.ServeCOAP(nil, nil, msg)
+	m.ServeCOAP(nil, nil, msg)
 
 	if msgs["a"] != 2 {
 		t.Errorf("Expected 2 messages for /a, got %v", msgs["a"])
 	}
 	if msgs["b"] != 1 {
 		t.Errorf("Expected 1 message for /b, got %v", msgs["b"])
 	}
+	if msgs[""] != 2 {
+		t.Errorf("Expected 2 message for /, got %v", msgs[""])
+	}
 }
 
 func TestPathMatch(t *testing.T) {
 	tests := []struct {
 		pattern, path string
 		exp           bool
 	}{
-		{"", "", false},
+		{"", "", true},
+		{"/", "/", true},
 		{"/a/b/c", "/a/b/c", true},
 		{"/a/b/c", "/a/b/c/d", false},
 		{"/a/b/c/", "/a/b/c/d", true},