why errkit when we already have errorutil ?

Introduced a year ago, errorutil aimed to capture error stacks for identifying deeply nested errors. However, its approach deviates from Go's error handling paradigm. In Go, libraries like "errors", "pkg/errors", and "uber.go/multierr" avoid using the .Error() method directly. Instead, they wrap errors with helper structs that implement specific interfaces, facilitating error chain traversal and the use of helper functions like .Cause() error or .Unwrap() error or errors.Is(). Contrarily, errorutil marshals errors to strings, which is incompatible with Go's error handling paradigm. Over time, the use of errorutil has become cumbersome due to its inability to replace any error package seamlessly and its lack of support for idiomatic error propagation or traversal in Go.

errkit is a new error library that addresses the shortcomings of errorutil. It offers the following features:

• Seamless replacement for existing error packages, requiring no syntax changes or refactoring:
  • errors package
  • pkg/errors package (now deprecated)
  • uber/multierr package
• errkit is compatible with all known Go error handling implementations. It can parse errors from any library and works with existing error handling libraries and helper functions like Is(), As(), Cause(), and more.
• errkit is Go idiomatic and adheres to the Go error handling paradigm.
• errkit supports attributes for structured error information or logging using slog.Attr (optional).
• errkit implements and categorizes errors into different kinds, as detailed below.
  • ErrKindNetworkTemporary
  • ErrKindNetworkPermanent
  • ErrKindDeadline
  • Custom kinds via ErrKind interface
• errkit provides helper functions for structured error logging using SlogAttrs and SlogAttrGroup.
• errkit offers helper functions to implement public or user-facing errors by using error kinds interface.

Attributes Support

errkit supports optional error wrapping with attributes slog.Attr for structured error logging, providing a more organized approach to error logging than string wrapping.

// normal way of error propogating through nested stack
err := errkit.New("i/o timeout")

// xyz.go
err := errkit.Wrap(err,"failed to connect %s",addr)

// abc.go
err := errkit.Wrap(err,"error occured when downloading %s",xyz)

with attributes support you can do following

// normal way of error propogating through nested stack
err := errkit.New("i/o timeout")

// xyz.go
err = errkit.WithAttr(err,slog.Any("resource",domain))

// abc.go
err = errkit.WithAttr(err,slog.Any("action","download"))

To keep errors concise and avoid unnecessary allocations, message wrapping and attributes count have a max depth set to 3. Adding more will not panic but will be simply ignored. This is configurable using the MAX_ERR_DEPTH env variable (default 3).