[VOL-3187]Pass Context down the execution call hierarchy across ofagent codebase
Change-Id: Ia5f2fa1509beefe0ddc427b83e39d2702782db8f
diff --git a/vendor/github.com/pkg/errors/errors.go b/vendor/github.com/pkg/errors/errors.go
new file mode 100644
index 0000000..7421f32
--- /dev/null
+++ b/vendor/github.com/pkg/errors/errors.go
@@ -0,0 +1,282 @@
+// Package errors provides simple error handling primitives.
+//
+// The traditional error handling idiom in Go is roughly akin to
+//
+// if err != nil {
+// return err
+// }
+//
+// which when 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,
+// together with 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: annotating an error with a stack trace and with 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 that 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
+// }
+//
+// Although the causer interface is not exported by this package, it is
+// considered a part of its stable public interface.
+//
+// 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
+// }
+//
+// The returned errors.StackTrace type 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)
+// }
+// }
+//
+// Although the stackTracer interface is not exported by this package, it is
+// considered a part of its stable public interface.
+//
+// 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 called, 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,
+ }
+}
+
+// WithMessagef annotates err with the format specifier.
+// If err is nil, WithMessagef returns nil.
+func WithMessagef(err error, format string, args ...interface{}) error {
+ if err == nil {
+ return nil
+ }
+ return &withMessage{
+ cause: err,
+ msg: fmt.Sprintf(format, args...),
+ }
+}
+
+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
+}