diff options
Diffstat (limited to 'vendor/github.com/pkg/errors/errors.go')
| -rw-r--r-- | vendor/github.com/pkg/errors/errors.go | 269 |
1 files changed, 269 insertions, 0 deletions
diff --git a/vendor/github.com/pkg/errors/errors.go b/vendor/github.com/pkg/errors/errors.go new file mode 100644 index 000000000..842ee8045 --- /dev/null +++ b/vendor/github.com/pkg/errors/errors.go @@ -0,0 +1,269 @@ +// Package errors provides simple error handling primitives. +// +// The traditional error handling idiom in Go is roughly akin to +// +// if err != nil { +// return err +// } +// +// which applied recursively up the call stack results in error reports +// without context or debugging information. The errors package allows +// programmers to add context to the failure path in their code in a way +// that does not destroy the original value of the error. +// +// Adding context to an error +// +// The errors.Wrap function returns a new error that adds context to the +// original error by recording a stack trace at the point Wrap is called, +// and the supplied message. For example +// +// _, err := ioutil.ReadAll(r) +// if err != nil { +// return errors.Wrap(err, "read failed") +// } +// +// If additional control is required the errors.WithStack and errors.WithMessage +// functions destructure errors.Wrap into its component operations of annotating +// an error with a stack trace and an a message, respectively. +// +// Retrieving the cause of an error +// +// Using errors.Wrap constructs a stack of errors, adding context to the +// preceding error. Depending on the nature of the error it may be necessary +// to reverse the operation of errors.Wrap to retrieve the original error +// for inspection. Any error value which implements this interface +// +// type causer interface { +// Cause() error +// } +// +// can be inspected by errors.Cause. errors.Cause will recursively retrieve +// the topmost error which does not implement causer, which is assumed to be +// the original cause. For example: +// +// switch err := errors.Cause(err).(type) { +// case *MyError: +// // handle specifically +// default: +// // unknown error +// } +// +// causer interface is not exported by this package, but is considered a part +// of stable public API. +// +// Formatted printing of errors +// +// All error values returned from this package implement fmt.Formatter and can +// be formatted by the fmt package. The following verbs are supported +// +// %s print the error. If the error has a Cause it will be +// printed recursively +// %v see %s +// %+v extended format. Each Frame of the error's StackTrace will +// be printed in detail. +// +// Retrieving the stack trace of an error or wrapper +// +// New, Errorf, Wrap, and Wrapf record a stack trace at the point they are +// invoked. This information can be retrieved with the following interface. +// +// type stackTracer interface { +// StackTrace() errors.StackTrace +// } +// +// Where errors.StackTrace is defined as +// +// type StackTrace []Frame +// +// The Frame type represents a call site in the stack trace. Frame supports +// the fmt.Formatter interface that can be used for printing information about +// the stack trace of this error. For example: +// +// if err, ok := err.(stackTracer); ok { +// for _, f := range err.StackTrace() { +// fmt.Printf("%+s:%d", f) +// } +// } +// +// stackTracer interface is not exported by this package, but is considered a part +// of stable public API. +// +// See the documentation for Frame.Format for more details. +package errors + +import ( + "fmt" + "io" +) + +// New returns an error with the supplied message. +// New also records the stack trace at the point it was called. +func New(message string) error { + return &fundamental{ + msg: message, + stack: callers(), + } +} + +// Errorf formats according to a format specifier and returns the string +// as a value that satisfies error. +// Errorf also records the stack trace at the point it was called. +func Errorf(format string, args ...interface{}) error { + return &fundamental{ + msg: fmt.Sprintf(format, args...), + stack: callers(), + } +} + +// fundamental is an error that has a message and a stack, but no caller. +type fundamental struct { + msg string + *stack +} + +func (f *fundamental) Error() string { return f.msg } + +func (f *fundamental) Format(s fmt.State, verb rune) { + switch verb { + case 'v': + if s.Flag('+') { + io.WriteString(s, f.msg) + f.stack.Format(s, verb) + return + } + fallthrough + case 's': + io.WriteString(s, f.msg) + case 'q': + fmt.Fprintf(s, "%q", f.msg) + } +} + +// WithStack annotates err with a stack trace at the point WithStack was called. +// If err is nil, WithStack returns nil. +func WithStack(err error) error { + if err == nil { + return nil + } + return &withStack{ + err, + callers(), + } +} + +type withStack struct { + error + *stack +} + +func (w *withStack) Cause() error { return w.error } + +func (w *withStack) Format(s fmt.State, verb rune) { + switch verb { + case 'v': + if s.Flag('+') { + fmt.Fprintf(s, "%+v", w.Cause()) + w.stack.Format(s, verb) + return + } + fallthrough + case 's': + io.WriteString(s, w.Error()) + case 'q': + fmt.Fprintf(s, "%q", w.Error()) + } +} + +// Wrap returns an error annotating err with a stack trace +// at the point Wrap is called, and the supplied message. +// If err is nil, Wrap returns nil. +func Wrap(err error, message string) error { + if err == nil { + return nil + } + err = &withMessage{ + cause: err, + msg: message, + } + return &withStack{ + err, + callers(), + } +} + +// Wrapf returns an error annotating err with a stack trace +// at the point Wrapf is call, and the format specifier. +// If err is nil, Wrapf returns nil. +func Wrapf(err error, format string, args ...interface{}) error { + if err == nil { + return nil + } + err = &withMessage{ + cause: err, + msg: fmt.Sprintf(format, args...), + } + return &withStack{ + err, + callers(), + } +} + +// WithMessage annotates err with a new message. +// If err is nil, WithMessage returns nil. +func WithMessage(err error, message string) error { + if err == nil { + return nil + } + return &withMessage{ + cause: err, + msg: message, + } +} + +type withMessage struct { + cause error + msg string +} + +func (w *withMessage) Error() string { return w.msg + ": " + w.cause.Error() } +func (w *withMessage) Cause() error { return w.cause } + +func (w *withMessage) Format(s fmt.State, verb rune) { + switch verb { + case 'v': + if s.Flag('+') { + fmt.Fprintf(s, "%+v\n", w.Cause()) + io.WriteString(s, w.msg) + return + } + fallthrough + case 's', 'q': + io.WriteString(s, w.Error()) + } +} + +// Cause returns the underlying cause of the error, if possible. +// An error value has a cause if it implements the following +// interface: +// +// type causer interface { +// Cause() error +// } +// +// If the error does not implement Cause, the original error will +// be returned. If the error is nil, nil will be returned without further +// investigation. +func Cause(err error) error { + type causer interface { + Cause() error + } + + for err != nil { + cause, ok := err.(causer) + if !ok { + break + } + err = cause.Cause() + } + return err +} |