Yet another errors package for Go.

Import as; godoc.

This is based on the new errors API introduced in Go 1.13 with the additions:

  1. Add Wrap(err, "some context") and Wrapf(err, "some context", ...), which return nil if the passed error is nil.

    I tried using the fmt.Errorf("...: %w", err) pattern, but I found I missed being able to do:

    func f() error {
        return errors.Wrap(f2(), "context")

    Which I find much more convenient than:

    func f() error {
        err := f2()
        if err != nil {
            return fmt.Errorf("context: %w", err)
        return nil
  2. A stack trace is added with erorrs.New(), errors.Errorf(), and erorrs.Wrap() I know it's not needed with appropriate context but sometimes I accidentally add the same context more than once, or just want to quickly see where exactly the error is coming from. Especially on dev it's much more convenient.

    You can use errors.Package to only add stack traces for a specific package. For example errors.Package = "" will only add trace lines in

    You can control the maximum stack size with errors.StackSize; set to 0 to disable adding stack traces altogether (i.e. on production).

  3. Group type for collecting grouped errors:

     errs := NewGroup(20)  // 20 is the maximum amount of errors
     for {
         err := doStuff()
         if err.Append(err) { // Won't append on nil, returns false if it's nil.
     fmt.Println(errs)        // Print all errors (if any).
     return errs.ErrorOrNil() // No errors? Returns nil.
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    Package errors adds some useful error helpers.



    This section is empty.


    View Source
    var (
    	// Package to add trace lines for; if blank all traces are added.
    	Package string
    	// StackSize is the maximum stack sized added to errors. Set to 0 to
    	// disable.
    	StackSize int = 32


    func As

    func As(err error, target interface{}) bool

    func Errorf

    func Errorf(f string, a ...interface{}) error

    func Is

    func Is(err, target error) bool

    func New

    func New(text string) error

    func Unwrap

    func Unwrap(err error) error

    func Wrap

    func Wrap(err error, s string) error

      Wrap an error with fmt.Errorf(), returning nil if err is nil.

      func Wrapf

      func Wrapf(err error, format string, a ...interface{}) error

        Wrapf an error with fmt.Errorf(), returning nil if err is nil.


        type Group

        type Group struct {
        	// Maximum number of errors; calls to Append() won't do anything if the
        	// number of errors is larger than this.
        	MaxSize int
        	// contains filtered or unexported fields

          Group multiple errors.

          func NewGroup

          func NewGroup(maxSize int) *Group

            NewGroup create a new Group instance. It will record a maximum of maxSize errors. Set to 0 for no limit.

            func (*Group) Append

            func (g *Group) Append(err error) bool

              Append a new error to the list; this is thread-safe.

              It won't do anything if the error is nil, in which case it will return false. This makes appending errors in a loop slightly nicer:

              for {
                  err := do()
                  if errors.Append(err) {

              func (Group) Error

              func (g Group) Error() string

              func (*Group) ErrorOrNil

              func (g *Group) ErrorOrNil() error

                ErrorOrNil returns itself if there are errors, or nil otherwise.

                It avoids an if-check at the end:

                return errs.ErrorOrNil()

                func (Group) Len

                func (g Group) Len() int

                  Len returns the number of errors.

                  type StackErr

                  type StackErr struct {
                  	// contains filtered or unexported fields

                  func (StackErr) Error

                  func (err StackErr) Error() string

                  func (StackErr) StackTrace

                  func (err StackErr) StackTrace() string

                  func (StackErr) Unwrap

                  func (err StackErr) Unwrap() error

                  type StackTracer

                  type StackTracer interface {
                  	StackTrace() string

                  Source Files