contextjson: Add context to decode error message

common/contextjson/decode_context.go

@@ -0,0 +1,49 @@
+package json
+
+import "strconv"
+
+type decodeContext struct {
+	parent *decodeContext
+	index  int
+	key    string
+}
+
+func (d *decodeState) formatContext() string {
+	var description string
+	context := d.context
+	var appendDot bool
+	for context != nil {
+		if appendDot {
+			description = "." + description
+		}
+		if context.key != "" {
+			description = context.key + description
+			appendDot = true
+		} else {
+			description = "[" + strconv.Itoa(context.index) + "]" + description
+			appendDot = false
+		}
+		context = context.parent
+	}
+	return description
+}
+
+type contextError struct {
+	parent  error
+	context string
+	index   bool
+}
+
+func (c *contextError) Unwrap() error {
+	return c.parent
+}
+
+func (c *contextError) Error() string {
+	//goland:noinspection GoTypeAssertionOnErrors
+	switch c.parent.(type) {
+	case *contextError:
+		return c.context + "." + c.parent.Error()
+	default:
+		return c.context + ": " + c.parent.Error()
+	}
+}