Xerrors

xerrors is a Go package from the golang.org/x/xerrors module that provides enhanced error handling features used before the Go standard library gained comparable capabilities. It was created to address limitations in early Go error handling by offering simple wrappers, stack traces, and a more expressive way to annotate and inspect errors.

Key features include error wrapping and contextual messages, stack traces, and a mechanism to retrieve the original underlying error. With xerrors, developers could wrap an error with additional context using functions like Wrap and Errorf, and attach a stack trace to an error using WithStack. Printed output could include a detailed stack trace when using the verbose formatting verb %+v, while the standard %v displayed only the error message. The package also exposes a helper like Cause to obtain the root cause of a wrapped error.

Usage typically involves importing golang.org/x/xerrors and then creating or propagating errors as the program flows. For example, Errorf can create formatted errors, Wrap can add context to an existing error, WithStack can attach a stack trace, and Cause can reveal the original error in a chain. Stack traces and formatting behavior are designed to aid debugging, especially in longer error chains.

Status and relationship to the standard library: with the introduction of Go 1.13, the standard errors package gained native wrapping, unwrapping, and inspection capabilities (Is, As, Unwrap) and the %w verb for wrapping. As a result, xerrors is now considered legacy for many projects, and migration toward the standard library is encouraged. The xerrors module remains available for legacy code, though ongoing maintenance has declined in favor of the standard library.