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@howbazaar @spring1843 @hiveminded
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// Copyright 2014 Canonical Ltd.
// Licensed under the LGPLv3, see LICENCE file for details.
package errors
import (
"fmt"
"strings"
)
// New is a drop in replacement for the standard library errors module that records
// the location that the error is created.
//
// For example:
// return errors.New("validation failed")
//
func New(message string) error {
err := &Err{message: message}
err.SetLocation(1)
return err
}
// Errorf creates a new annotated error and records the location that the
// error is created. This should be a drop in replacement for fmt.Errorf.
//
// For example:
// return errors.Errorf("validation failed: %s", message)
//
func Errorf(format string, args ...interface{}) error {
err := &Err{message: fmt.Sprintf(format, args...)}
err.SetLocation(1)
return err
}
// Trace adds the location of the Trace call to the stack. The Cause of the
// resulting error is the same as the error parameter. If the other error is
// nil, the result will be nil.
//
// For example:
// if err := SomeFunc(); err != nil {
// return errors.Trace(err)
// }
//
func Trace(other error) error {
if other == nil {
return nil
}
err := &Err{previous: other, cause: Cause(other)}
err.SetLocation(1)
return err
}
// Annotate is used to add extra context to an existing error. The location of
// the Annotate call is recorded with the annotations. The file, line and
// function are also recorded.
//
// For example:
// if err := SomeFunc(); err != nil {
// return errors.Annotate(err, "failed to frombulate")
// }
//
func Annotate(other error, message string) error {
if other == nil {
return nil
}
err := &Err{
previous: other,
cause: Cause(other),
message: message,
}
err.SetLocation(1)
return err
}
// Annotatef is used to add extra context to an existing error. The location of
// the Annotate call is recorded with the annotations. The file, line and
// function are also recorded.
//
// For example:
// if err := SomeFunc(); err != nil {
// return errors.Annotatef(err, "failed to frombulate the %s", arg)
// }
//
func Annotatef(other error, format string, args ...interface{}) error {
if other == nil {
return nil
}
err := &Err{
previous: other,
cause: Cause(other),
message: fmt.Sprintf(format, args...),
}
err.SetLocation(1)
return err
}
// DeferredAnnotatef annotates the given error (when it is not nil) with the given
// format string and arguments (like fmt.Sprintf). If *err is nil, DeferredAnnotatef
// does nothing. This method is used in a defer statement in order to annotate any
// resulting error with the same message.
//
// For example:
//
// defer DeferredAnnotatef(&err, "failed to frombulate the %s", arg)
//
func DeferredAnnotatef(err *error, format string, args ...interface{}) {
if *err == nil {
return
}
newErr := &Err{
message: fmt.Sprintf(format, args...),
cause: Cause(*err),
previous: *err,
}
newErr.SetLocation(1)
*err = newErr
}
// Wrap changes the Cause of the error. The location of the Wrap call is also
// stored in the error stack.
//
// For example:
// if err := SomeFunc(); err != nil {
// newErr := &packageError{"more context", private_value}
// return errors.Wrap(err, newErr)
// }
//
func Wrap(other, newDescriptive error) error {
err := &Err{
previous: other,
cause: newDescriptive,
}
err.SetLocation(1)
return err
}
// Wrapf changes the Cause of the error, and adds an annotation. The location
// of the Wrap call is also stored in the error stack.
//
// For example:
// if err := SomeFunc(); err != nil {
// return errors.Wrapf(err, simpleErrorType, "invalid value %q", value)
// }
//
func Wrapf(other, newDescriptive error, format string, args ...interface{}) error {
err := &Err{
message: fmt.Sprintf(format, args...),
previous: other,
cause: newDescriptive,
}
err.SetLocation(1)
return err
}
// Maskf masks the given error with the given format string and arguments (like
// fmt.Sprintf), returning a new error that maintains the error stack, but
// hides the underlying error type. The error string still contains the full
// annotations. If you want to hide the annotations, call Wrap.
func Maskf(other error, format string, args ...interface{}) error {
if other == nil {
return nil
}
err := &Err{
message: fmt.Sprintf(format, args...),
previous: other,
}
err.SetLocation(1)
return err
}
// Mask hides the underlying error type, and records the location of the masking.
func Mask(other error) error {
if other == nil {
return nil
}
err := &Err{
previous: other,
}
err.SetLocation(1)
return err
}
// Cause returns the cause of the given error. This will be either the
// original error, or the result of a Wrap or Mask call.
//
// Cause is the usual way to diagnose errors that may have been wrapped by
// the other errors functions.
func Cause(err error) error {
var diag error
if err, ok := err.(causer); ok {
diag = err.Cause()
}
if diag != nil {
return diag
}
return err
}
type causer interface {
Cause() error
}
type wrapper interface {
// Message returns the top level error message,
// not including the message from the Previous
// error.
Message() string
// Underlying returns the Previous error, or nil
// if there is none.
Underlying() error
}
type locationer interface {
Location() (string, int)
}
var (
_ wrapper = (*Err)(nil)
_ locationer = (*Err)(nil)
_ causer = (*Err)(nil)
)
// Details returns information about the stack of errors wrapped by err, in
// the format:
//
// [{filename:99: error one} {otherfile:55: cause of error one}]
//
// This is a terse alternative to ErrorStack as it returns a single line.
func Details(err error) string {
if err == nil {
return "[]"
}
var s []byte
s = append(s, '[')
for {
s = append(s, '{')
if err, ok := err.(locationer); ok {
file, line := err.Location()
if file != "" {
s = append(s, fmt.Sprintf("%s:%d", file, line)...)
s = append(s, ": "...)
}
}
if cerr, ok := err.(wrapper); ok {
s = append(s, cerr.Message()...)
err = cerr.Underlying()
} else {
s = append(s, err.Error()...)
err = nil
}
s = append(s, '}')
if err == nil {
break
}
s = append(s, ' ')
}
s = append(s, ']')
return string(s)
}
// ErrorStack returns a string representation of the annotated error. If the
// error passed as the parameter is not an annotated error, the result is
// simply the result of the Error() method on that error.
//
// If the error is an annotated error, a multi-line string is returned where
// each line represents one entry in the annotation stack. The full filename
// from the call stack is used in the output.
//
// first error
// github.com/juju/errors/annotation_test.go:193:
// github.com/juju/errors/annotation_test.go:194: annotation
// github.com/juju/errors/annotation_test.go:195:
// github.com/juju/errors/annotation_test.go:196: more context
// github.com/juju/errors/annotation_test.go:197:
func ErrorStack(err error) string {
return strings.Join(errorStack(err), "\n")
}
func errorStack(err error) []string {
if err == nil {
return nil
}
// We want the first error first
var lines []string
for {
var buff []byte
if err, ok := err.(locationer); ok {
file, line := err.Location()
// Strip off the leading GOPATH/src path elements.
file = trimGoPath(file)
if file != "" {
buff = append(buff, fmt.Sprintf("%s:%d", file, line)...)
buff = append(buff, ": "...)
}
}
if cerr, ok := err.(wrapper); ok {
message := cerr.Message()
buff = append(buff, message...)
// If there is a cause for this error, and it is different to the cause
// of the underlying error, then output the error string in the stack trace.
var cause error
if err1, ok := err.(causer); ok {
cause = err1.Cause()
}
err = cerr.Underlying()
if cause != nil && !sameError(Cause(err), cause) {
if message != "" {
buff = append(buff, ": "...)
}
buff = append(buff, cause.Error()...)
}
} else {
buff = append(buff, err.Error()...)
err = nil
}
lines = append(lines, string(buff))
if err == nil {
break
}
}
// reverse the lines to get the original error, which was at the end of
// the list, back to the start.
var result []string
for i := len(lines); i > 0; i-- {
result = append(result, lines[i-1])
}
return result
}
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