github.com/pkg/errors

What's new since version 0.6.0

0.7.0 removes the deprecated errors.Location and errors.Stack interfaces, and the errors.Fprint helper. Types returned from this package now implement the fmt.Formatter interface and can print themselves when passed to fmt.Printf and friends.

For example:

• fmt.Printf("%s\n", err) will print the message of the error as per normal, recursive if the underlying error has a Cause method.
• fmt.Printf(%v\n", err) operates the same as %s.
• fmt.Printf(%+v\n", err) prints the error message as above, then prints a stack trace of the point that the error was created with errors.New, errors.Errorf, etc.

This new behaviour is described in this blog post.

Other changes in 0.7.0 include:

• The Stacktrace() []Frame interface method was renamed to StackTrace() StackTrace. Please note the change in capitalisation. The previous interface was added in 0.6.0 so hopefully this change will not cause to many breaking changes. The name and signature of the method is not expected to change again in the future. Fixes #50.

Bug fixes

• README.md incorrectly reported the licence of this package as MIT, not BSD 2 clause, this has been rectified. Thanks @anthonyfok. Fixes #41.

What's new since version 0.5.1

The 0.6.0 release is a transitional release aimed at exposing the error's call stack, introduced in 0.5.0, to the caller.

0.6.0 is the last release that will support the errors.Fprint helper function. This function will be removed in version 0.7 and will be replaced with a more flexible option based on the fmt.Formatter interface.

Many thanks to @ChrisHines for inspiration, via his go-stack/stack package, and for his thoughtful review feedback.

Deprecation notice

The following symbols have been deprecated and will be removed in future releases.

• errors.Fprintf will be removed in the 0.7 release. Read on for more details.
• The Location interface,

type location interface {
        Location() (string, int)
}

is deprecated and will not be recognised in future releases. The replacement is

fmt.Sprintf("%+v", err.Stacktrace()[0])

That is, pass the topmost element of error's stack trace (assuming it has a Stacktrace() []Frame method) to fmt and print it with the %+v verb.

• The Stack interface,

type stack interface {
        Stack() []uintptr
}

is deprecated and will not be recognised in future releases. Callers should use the new Stacktrace interface described below.

New features

• Stacktrace interface. As a replacement for the deprecated Stack() []uintptr interface, implementations in this package now support a Stacktrace interface

type Stacktrace interface {
         Stacktrace() []Frame
}

Calling this method returns a slice of Frame values, the most recent on the top. See #37

• Frame values replace raw uintptr's (representing program counters) providing a type which implement the fmt.Formatter interface, which in turn exposes various aspect of a call frame (name, source file and line, etc) via the fmt package. See also #37
• The name of the formal parameter to Wrap and Wrapf has been renamed from cause to err. This reflects the nature of these functions; to create a stack of errors. Apparently this also helps editor auto completion. Thanks @matryer. Fixes #32

Bugs fixed

• Fix a bug whereby errors returned by New, Errorf, Wrap, Wrapf were not comparable with ==. Thanks to @stevvooe. Fixes #29

What's new

• New, Errorf, Wrap, and Wrapf, now store the stack trace of their caller (currently limited to a depth of 32). This can be retrieved by asserting for the following interface

type Stack interface {
        Stack() []uintptr
}

The resulting []uintptr is the same format as runtime.Callers. At the moment there are no helpers to inspect this information.

What's new

• Remove the errors.Print helper, callers should use errors.Fprint(os.Stderr, err) as a replacement. See #23 for details
• README.md now has syntax highlighting. Thanks @mustafaakin
• Package short description has been revised based. See #24 for details.