Hi, thanks for the PR!

How about enhancing prettyJSON to handle both JSON strings and JSON objects(map[string]any) directly, instead of introducing the pretty flag for json? This change might simplify the usage and make it more intuitive.

Updated prettyJSON

Since Go templates cannot handle errors, it returns the original string if an error occurs.

		"prettyJSON": func(value any) string {
			var data map[string]any

			switch v := value.(type) {
			case string:
				if err := json.Unmarshal([]byte(v), &data); err != nil {
					return v
				}
			case map[string]any:
				data = v
			default:
				return fmt.Sprintf("%v", value)
			}

			b, err := json.MarshalIndent(data, "", "  ")
			if err != nil {
				return fmt.Sprintf("%v", value)
			}

			return string(b)
		},

Example: Handling JSON strings

dist/stern --stdin --template \
  '{{ .Message | prettyJSON }}{{"\n"}}' <<EOS
{"level":"info","ts":1257894000,"caller":"sandbox2210433069/prog.go:10","msg":"hello","key1":"val1"}
{"level":"info","ts":1257894000,"caller":"sandbox2210433069/prog.go:13","msg":"world","key1":"val1"}
invalid json
EOS

Invalid JSON strings (such as invalid json) are printed as is.

{
  "caller": "sandbox2210433069/prog.go:10",
  "key1": "val1",
  "level": "info",
  "msg": "hello",
  "ts": 1257894000
}
{
  "caller": "sandbox2210433069/prog.go:13",
  "key1": "val1",
  "level": "info",
  "msg": "world",
  "ts": 1257894000
}
invalid json

Example: Handling JSON objects

dist/stern --stdin --template \
  '{{ with $msg := .Message | tryParseJSON }}{{ prettyJSON $msg }}{{"\n"}}{{end}}' <<EOS
{"level":"info","ts":1257894000,"caller":"sandbox2210433069/prog.go:10","msg":"hello","key1":"val1"}
{"level":"info","ts":1257894000,"caller":"sandbox2210433069/prog.go:13","msg":"world","key1":"val1"}
invalid json
EOS

Invalid JSON strings (such as invalid json) are ignored because of the with clause.

{
  "caller": "sandbox2210433069/prog.go:10",
  "key1": "val1",
  "level": "info",
  "msg": "hello",
  "ts": 1257894000
}
{
  "caller": "sandbox2210433069/prog.go:13",
  "key1": "val1",
  "level": "info",
  "msg": "world",
  "ts": 1257894000
}

Awesome, will do that.

@tksm I pushed your suggestion, let me know

I guess I should update the doc as well, but I want to wait for your review before doing that

LGTM for the prettyJSON func 👍

📝 I have already removed extjson and ppextjson from the template function list in #325, but thank you for updating it anyway.

LGTM for the prettyJSON func 👍

I added some examples in the readme and removed outdated options.

Hello, I just found this and would love to try to use it but it looks like it hasn't been released. Any chance you could cut a new version? Thanks!

I've just released a new version. Thanks. https://github.com/stern/stern/releases/tag/v1.32.0