badjson: Add UnmarshalExtended

Author: nekohasekai

common/json/unmarshal.go

@@ -0,0 +1,25 @@
+package json
+
+import (
+	"bytes"
+	"strings"
+
+	"github.com/sagernet/sing/common"
+	E "github.com/sagernet/sing/common/exceptions"
+)
+
+func UnmarshalExtended[T any](content []byte) (T, error) {
+	decoder := NewDecoder(NewCommentFilter(bytes.NewReader(content)))
+	var value T
+	err := decoder.Decode(&value)
+	if err == nil {
+		return value, err
+	}
+	if syntaxError, isSyntaxError := err.(*SyntaxError); isSyntaxError {
+		prefix := string(content[:syntaxError.Offset])
+		row := strings.Count(prefix, "\n") + 1
+		column := len(prefix) - strings.LastIndex(prefix, "\n") - 1
+		return common.DefaultValue[T](), E.Extend(syntaxError, "row ", row, ", column ", column)
+	}
+	return common.DefaultValue[T](), err
+}