From 2c32e3e6bfd9649e32af9d7708fba0e1f6cb7952 Mon Sep 17 00:00:00 2001
From: "Alexander A. Klimov" <grandmaster@al2klimov.de>
Date: Sat, 19 Jun 2021 01:01:23 +0200
Subject: [PATCH] JSONFormatter#Format(): let errors decide their JSON
 representation by themselves

... if they implement json.Marshaler or encoding.TextMarshaler.
---
 json_formatter.go | 5 +++++
 1 file changed, 5 insertions(+)

diff --git a/json_formatter.go b/json_formatter.go
index c96dc5636..cb733afb6 100644
--- a/json_formatter.go
+++ b/json_formatter.go
@@ -2,6 +2,7 @@ package logrus
 
 import (
 	"bytes"
+	"encoding"
 	"encoding/json"
 	"fmt"
 	"runtime"
@@ -64,6 +65,10 @@ func (f *JSONFormatter) Format(entry *Entry) ([]byte, error) {
 	data := make(Fields, len(entry.Data)+4)
 	for k, v := range entry.Data {
 		switch v := v.(type) {
+		case json.Marshaler, encoding.TextMarshaler:
+			// Let errors which implement either of these
+			// decide their JSON representation by themselves.
+			data[k] = v
 		case error:
 			// Otherwise errors are ignored by `encoding/json`
 			// https://github.com/sirupsen/logrus/issues/137