jerror

Package jerror is a helper to create errors. It supports creating parametrized messages to give more information on the error and easier way of wrapping. These errors are compatible with standard errors.Is and errors.Unwrap.

Examples

Basic usage

// create a new type, it has a string placeholder
ErrCannotOpen := jerror.New("can not open file %s")

fileName := "file.txt"
err := os.Open(fileName)
if err != nil {
		// new intance of the error, sets the placeholder and wraps an error. The
		// error returned is:
		// 		can not open file file.txt: file does not exist
    return ErrCannotOpen.New().Args(fileName).Wrap(err)
}

Error stack trace

It also generates a stack trace when the error is created, so you can see where the error was created.

ErrExample := jerror.New("error")
err := ErrExample.New()
spew.Dump(err.Frames())
// ([]jerror.Frame) (len=3 cap=4) {
//  (jerror.Frame) {
//   Function: (string) (len=35) "github.com/jfontan/jerror.TestStack",
//   File: (string) (len=44) "/home/jfontan/projects/jerror/jerror_test.go",
//   Line: (int) 97
//  },
//  (jerror.Frame) {
//   Function: (string) (len=15) "testing.tRunner",
//   File: (string) (len=34) "/usr/lib/go/src/testing/testing.go",
//   Line: (int) 1689
//  },
//  (jerror.Frame) {
//   Function: (string) (len=14) "runtime.goexit",
//   File: (string) (len=35) "/usr/lib/go/src/runtime/asm_amd64.s",
//   Line: (int) 1695
//  }
// }

Set error values

You can set and retrieve values from an error:

jerr := jerror.New("cannot open file")
err := jerr.Set("path", "/some/path.txt")
val, _ := err.GetString("path")
fmt.Println(val)
// /some/path.txt

Generate slog attributes

It can also generate slog compatible attributes to log the error and of there is older errors it also gives information about the oldest error:

jerr2 := jerror.New("jerror 2").Set("key", "value 2")
jerr1 := jerror.New("jerror 1").Set("key", "value 1").Wrap(jerr2)

var buf bytes.Buffer
log := slog.New(slog.NewJSONHandler(&buf, &slog.HandlerOptions{}))
log.Error("message", jerr1.SlogAttributes("data", true))

var j any
_ = json.Unmarshal(buf.Bytes(), &j)
i, _ := json.MarshalIndent(j, "", "  ")
fmt.Println(string(i))
// {
//   "data": {
//     "error": "jerror 1: jerror 2",
//     "oldest_jerror": {
//       "error": "jerror 2",
//       "stack": {
//         "0": "github.com/jfontan/jerror/examples.TestSlog github.com/jfontan/jerror/examples/examples_test.go:14",
//         "1": "testing.tRunner testing/testing.go:1689",
//         "2": "runtime.goexit runtime/asm_amd64.s:1695"
//       },
//       "values": {
//         "key": "value 2"
//       }
//     },
//     "stack": {
//       "0": "github.com/jfontan/jerror/examples.TestSlog github.com/jfontan/jerror/examples/examples_test.go:15",
//       "1": "testing.tRunner testing/testing.go:1689",
//       "2": "runtime.goexit runtime/asm_amd64.s:1695"
//     },
//     "values": {
//       "key": "value 1"
//     }
//   },
//   "level": "ERROR",
//   "msg": "message",
//   "time": "2024-05-30T16:26:33.292105723+02:00"
// }