net/url: implement encoding.BinaryAppender for URL

For #62384

api/next/62384.txt

@@ -2,3 +2,4 @@ pkg encoding, type BinaryAppender interface { AppendBinary } #62384
 pkg encoding, type BinaryAppender interface, AppendBinary([]uint8) ([]uint8, error) #62384
 pkg encoding, type TextAppender interface { AppendText } #62384
 pkg encoding, type TextAppender interface, AppendText([]uint8) ([]uint8, error) #62384
+pkg net/url, method (*URL) AppendBinary([]uint8) ([]uint8, error) #62384

doc/next/6-stdlib/99-minor/net/url/62384.md

@@ -0,0 +1 @@
+[URL] now also implements the [encoding.BinaryAppender] interface.

src/net/url/url.go

@@ -1219,7 +1219,11 @@ func splitHostPort(hostPort string) (host, port string) {
 // Would like to implement MarshalText/UnmarshalText but that will change the JSON representation of URLs.
 
 func (u *URL) MarshalBinary() (text []byte, err error) {
-	return []byte(u.String()), nil
+	return u.AppendBinary(nil)
+}
+
+func (u *URL) AppendBinary(b []byte) ([]byte, error) {
+	return append(b, u.String()...), nil
 }
 
 func (u *URL) UnmarshalBinary(text []byte) error {

src/net/url/url_test.go

@@ -1866,6 +1866,7 @@ func TestURLHostnameAndPort(t *testing.T) {
 
 var _ encodingPkg.BinaryMarshaler = (*URL)(nil)
 var _ encodingPkg.BinaryUnmarshaler = (*URL)(nil)
+var _ encodingPkg.BinaryAppender = (*URL)(nil)
 
 func TestJSON(t *testing.T) {
 	u, err := Parse("https://www.google.com/x?y=z")