encoding/json: A JSON tag can be any valid JSON string.

Fixes #3887.

R=golang-dev, daniel.morsing, remyoudompheng, rsc
CC=golang-dev
https://golang.org/cl/6997045

src/pkg/encoding/json/encode.go

@@ -437,7 +437,7 @@ func isValidTag(s string) bool {
 	}
 	for _, c := range s {
 		switch {
-		case strings.ContainsRune("!#$%&()*+-./:<=>?@[]^_{|}~", c):
+		case strings.ContainsRune("!#$%&()*+-./:<=>?@[]^_{|}~ ", c):
 			// Backslash and quote chars are reserved, but
 			// otherwise any punctuation chars are allowed
 			// in a tag name.

src/pkg/encoding/json/tagkey_test.go

@@ -60,6 +60,14 @@ type badCodeTag struct {
 	Z string `json:" !\"#&'()*+,."`
 }
 
+type spaceTag struct {
+	Q string `json:"With space"`
+}
+
+type unicodeTag struct {
+	W string `json:"Ελλάδα"`
+}
+
 var structTagObjectKeyTests = []struct {
 	raw   interface{}
 	value string
@@ -78,6 +86,8 @@ var structTagObjectKeyTests = []struct {
 	{badCodeTag{"Reliable Man"}, "Reliable Man", "Z"},
 	{percentSlashTag{"brut"}, "brut", "text/html%"},
 	{punctuationTag{"Union Rags"}, "Union Rags", "!#$%&()*+-./:<=>?@[]^_{|}~"},
+	{spaceTag{"Perreddu"}, "Perreddu", "With space"},
+	{unicodeTag{"Loukanikos"}, "Loukanikos", "Ελλάδα"},
 }
 
 func TestStructTagObjectKey(t *testing.T) {