1 files changed, 30 insertions, 0 deletions
diff --git a/internal/jsonstruct/borrowed_misc.go b/internal/jsonstruct/borrowed_misc.go
new file mode 100644
index 0000000..3b4181e
--- /dev/null
+++ b/internal/jsonstruct/borrowed_misc.go
@@ -0,0 +1,30 @@
+// Copyright 2010 The Go Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+//
+// SPDX-License-Identifier: BSD-3-Clause
+
+package jsonstruct
+
+import (
+	"strings"
+	"unicode"
+)
+
+// isValidTag is borrowed from encode.go.
+func isValidTag(s string) bool {
+	if s == "" {
+		return false
+	}
+	for _, c := range s {
+		switch {
+		case strings.ContainsRune("!#$%&()*+-./:;<=>?@[]^_{|}~ ", c):
+			// Backslash and quote chars are reserved, but
+			// otherwise any punctuation chars are allowed
+			// in a tag name.
+		case !unicode.IsLetter(c) && !unicode.IsDigit(c):
+			return false
+		}
+	}
+	return true
+}