README.md - external/github.com/juju/errors - Git at Google


 # errors
     import "github.com/juju/errors"

 [![GoDoc](https://godoc.org/github.com/juju/errors?status.svg)](https://godoc.org/github.com/juju/errors)

 The juju/errors provides an easy way to annotate errors without losing the
 original error context.

 The exported `New` and `Errorf` functions are designed to replace the
 `errors.New` and `fmt.Errorf` functions respectively. The same underlying
 error is there, but the package also records the location at which the error
 was created.

 A primary use case for this library is to add extra context any time an
 error is returned from a function.


 	    if err := SomeFunc(); err != nil {
 		    return err
 		}

 This instead becomes:


 	    if err := SomeFunc(); err != nil {
 		    return errors.Trace(err)
 		}

 which just records the file and line number of the Trace call, or


 	    if err := SomeFunc(); err != nil {
 		    return errors.Annotate(err, "more context")
 		}

 which also adds an annotation to the error.

 When you want to check to see if an error is of a particular type, a helper
 function is normally exported by the package that returned the error, like the
 `os` package does.  The underlying cause of the error is available using the
 `Cause` function.


 	os.IsNotExist(errors.Cause(err))

 The result of the `Error()` call on an annotated error is the annotations joined
 with colons, then the result of the `Error()` method for the underlying error
 that was the cause.


 	err := errors.Errorf("original")
 	err = errors.Annotatef(err, "context")
 	err = errors.Annotatef(err, "more context")
 	err.Error() -> "more context: context: original"

 Obviously recording the file, line and functions is not very useful if you
 cannot get them back out again.


 	errors.ErrorStack(err)

 will return something like:


 	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:

 The first error was generated by an external system, so there was no location
 associated. The second, fourth, and last lines were generated with Trace calls,
 and the other two through Annotate.

 Sometimes when responding to an error you want to return a more specific error
 for the situation.


 	    if err := FindField(field); err != nil {
 		    return errors.Wrap(err, errors.NotFoundf(field))
 		}

 This returns an error where the complete error stack is still available, and
 `errors.Cause()` will return the `NotFound` error.


 ## func AlreadyExistsf
 ``` go
 func AlreadyExistsf(format string, args ...interface{}) error
 ```
 AlreadyExistsf returns an error which satisfies IsAlreadyExists().


 ## func Annotate
 ``` go
 func Annotate(other error, message string) error
 ```
 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 Annotatef
 ``` go
 func Annotatef(other error, format string, args ...interface{}) error
 ```
 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 BadRequestf
 ``` go
 func BadRequestf(format string, args ...interface{}) error
 ```
 BadRequestf returns an error which satisfies IsBadRequest().


 ## func Cause
 ``` go
 func Cause(err error) error
 ```
 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 DeferredAnnotatef
 ``` go
 func DeferredAnnotatef(err *error, format string, args ...interface{})
 ```
 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 Details
 ``` go
 func Details(err error) string
 ```
 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 ErrorStack
 ``` go
 func ErrorStack(err error) string
 ```
 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 Errorf
 ``` go
 func Errorf(format string, args ...interface{}) error
 ```
 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 Forbiddenf
 ``` go
 func Forbiddenf(format string, args ...interface{}) error
 ```
 Forbiddenf returns an error which satistifes IsForbidden()


 ## func IsAlreadyExists
 ``` go
 func IsAlreadyExists(err error) bool
 ```
 IsAlreadyExists reports whether the error was created with
 AlreadyExistsf() or NewAlreadyExists().


 ## func IsBadRequest
 ``` go
 func IsBadRequest(err error) bool
 ```
 IsBadRequest reports whether err was created with BadRequestf() or
 NewBadRequest().


 ## func IsForbidden
 ``` go
 func IsForbidden(err error) bool
 ```
 IsForbidden reports whether err was created with Forbiddenf() or
 NewForbidden().


 ## func IsMethodNotAllowed
 ``` go
 func IsMethodNotAllowed(err error) bool
 ```
 IsMethodNotAllowed reports whether err was created with MethodNotAllowedf() or
 NewMethodNotAllowed().


 ## func IsNotAssigned
 ``` go
 func IsNotAssigned(err error) bool
 ```
 IsNotAssigned reports whether err was created with NotAssignedf() or
 NewNotAssigned().


 ## func IsNotFound
 ``` go
 func IsNotFound(err error) bool
 ```
 IsNotFound reports whether err was created with NotFoundf() or
 NewNotFound().


 ## func IsNotImplemented
 ``` go
 func IsNotImplemented(err error) bool
 ```
 IsNotImplemented reports whether err was created with
 NotImplementedf() or NewNotImplemented().


 ## func IsNotProvisioned
 ``` go
 func IsNotProvisioned(err error) bool
 ```
 IsNotProvisioned reports whether err was created with NotProvisionedf() or
 NewNotProvisioned().


 ## func IsNotSupported
 ``` go
 func IsNotSupported(err error) bool
 ```
 IsNotSupported reports whether the error was created with
 NotSupportedf() or NewNotSupported().


 ## func IsNotValid
 ``` go
 func IsNotValid(err error) bool
 ```
 IsNotValid reports whether the error was created with NotValidf() or
 NewNotValid().


 ## func IsUnauthorized
 ``` go
 func IsUnauthorized(err error) bool
 ```
 IsUnauthorized reports whether err was created with Unauthorizedf() or
 NewUnauthorized().


 ## func IsUserNotFound
 ``` go
 func IsUserNotFound(err error) bool
 ```
 IsUserNotFound reports whether err was created with UserNotFoundf() or
 NewUserNotFound().


 ## func Mask
 ``` go
 func Mask(other error) error
 ```
 Mask hides the underlying error type, and records the location of the masking.


 ## func Maskf
 ``` go
 func Maskf(other error, format string, args ...interface{}) error
 ```
 Mask 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 MethodNotAllowedf
 ``` go
 func MethodNotAllowedf(format string, args ...interface{}) error
 ```
 MethodNotAllowedf returns an error which satisfies IsMethodNotAllowed().


 ## func New
 ``` go
 func New(message string) error
 ```
 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 NewAlreadyExists
 ``` go
 func NewAlreadyExists(err error, msg string) error
 ```
 NewAlreadyExists returns an error which wraps err and satisfies
 IsAlreadyExists().


 ## func NewBadRequest
 ``` go
 func NewBadRequest(err error, msg string) error
 ```
 NewBadRequest returns an error which wraps err that satisfies
 IsBadRequest().


 ## func NewForbidden
 ``` go
 func NewForbidden(err error, msg string) error
 ```
 NewForbidden returns an error which wraps err that satisfies
 IsForbidden().


 ## func NewMethodNotAllowed
 ``` go
 func NewMethodNotAllowed(err error, msg string) error
 ```
 NewMethodNotAllowed returns an error which wraps err that satisfies
 IsMethodNotAllowed().


 ## func NewNotAssigned
 ``` go
 func NewNotAssigned(err error, msg string) error
 ```
 NewNotAssigned returns an error which wraps err that satisfies
 IsNotAssigned().


 ## func NewNotFound
 ``` go
 func NewNotFound(err error, msg string) error
 ```
 NewNotFound returns an error which wraps err that satisfies
 IsNotFound().


 ## func NewNotImplemented
 ``` go
 func NewNotImplemented(err error, msg string) error
 ```
 NewNotImplemented returns an error which wraps err and satisfies
 IsNotImplemented().


 ## func NewNotProvisioned
 ``` go
 func NewNotProvisioned(err error, msg string) error
 ```
 NewNotProvisioned returns an error which wraps err that satisfies
 IsNotProvisioned().


 ## func NewNotSupported
 ``` go
 func NewNotSupported(err error, msg string) error
 ```
 NewNotSupported returns an error which wraps err and satisfies
 IsNotSupported().


 ## func NewNotValid
 ``` go
 func NewNotValid(err error, msg string) error
 ```
 NewNotValid returns an error which wraps err and satisfies IsNotValid().


 ## func NewUnauthorized
 ``` go
 func NewUnauthorized(err error, msg string) error
 ```
 NewUnauthorized returns an error which wraps err and satisfies
 IsUnauthorized().


 ## func NewUserNotFound
 ``` go
 func NewUserNotFound(err error, msg string) error
 ```
 NewUserNotFound returns an error which wraps err and satisfies
 IsUserNotFound().


 ## func NotAssignedf
 ``` go
 func NotAssignedf(format string, args ...interface{}) error
 ```
 NotAssignedf returns an error which satisfies IsNotAssigned().


 ## func NotFoundf
 ``` go
 func NotFoundf(format string, args ...interface{}) error
 ```
 NotFoundf returns an error which satisfies IsNotFound().


 ## func NotImplementedf
 ``` go
 func NotImplementedf(format string, args ...interface{}) error
 ```
 NotImplementedf returns an error which satisfies IsNotImplemented().


 ## func NotProvisionedf
 ``` go
 func NotProvisionedf(format string, args ...interface{}) error
 ```
 NotProvisionedf returns an error which satisfies IsNotProvisioned().


 ## func NotSupportedf
 ``` go
 func NotSupportedf(format string, args ...interface{}) error
 ```
 NotSupportedf returns an error which satisfies IsNotSupported().


 ## func NotValidf
 ``` go
 func NotValidf(format string, args ...interface{}) error
 ```
 NotValidf returns an error which satisfies IsNotValid().


 ## func Trace
 ``` go
 func Trace(other error) error
 ```
 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 Unauthorizedf
 ``` go
 func Unauthorizedf(format string, args ...interface{}) error
 ```
 Unauthorizedf returns an error which satisfies IsUnauthorized().


 ## func UserNotFoundf
 ``` go
 func UserNotFoundf(format string, args ...interface{}) error
 ```
 UserNotFoundf returns an error which satisfies IsUserNotFound().


 ## func Wrap
 ``` go
 func Wrap(other, newDescriptive error) error
 ```
 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 Wrapf
 ``` go
 func Wrapf(other, newDescriptive error, format string, args ...interface{}) error
 ```
 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)
 	}


 ## type Err
 ``` go
 type Err struct {
     // contains filtered or unexported fields
 }
 ```
 Err holds a description of an error along with information about
 where the error was created.

 It may be embedded in custom error types to add extra information that
 this errors package can understand.


 ### func NewErr
 ``` go
 func NewErr(format string, args ...interface{}) Err
 ```
 NewErr is used to return an Err for the purpose of embedding in other
 structures.  The location is not specified, and needs to be set with a call
 to SetLocation.

 For example:


 	type FooError struct {
 	    errors.Err
 	    code int
 	}

 	func NewFooError(code int) error {
 	    err := &FooError{errors.NewErr("foo"), code}
 	    err.SetLocation(1)
 	    return err
 	}


 ### func NewErrWithCause
 ``` go
 func NewErrWithCause(other error, format string, args ...interface{}) Err
 ```
 NewErrWithCause is used to return an Err with cause by other error for the purpose of embedding in other
 structures. The location is not specified, and needs to be set with a call
 to SetLocation.

 For example:


 	type FooError struct {
 	    errors.Err
 	    code int
 	}

 	func (e *FooError) Annotate(format string, args ...interface{}) error {
 	    err := &FooError{errors.NewErrWithCause(e.Err, format, args...), e.code}
 	    err.SetLocation(1)
 	    return err
 	})


 ### func (\*Err) Cause
 ``` go
 func (e *Err) Cause() error
 ```
 The Cause of an error is the most recent error in the error stack that
 meets one of these criteria: the original error that was raised; the new
 error that was passed into the Wrap function; the most recently masked
 error; or nil if the error itself is considered the Cause.  Normally this
 method is not invoked directly, but instead through the Cause stand alone
 function.


 ### func (\*Err) Error
 ``` go
 func (e *Err) Error() string
 ```
 Error implements error.Error.


 ### func (\*Err) Format
 ``` go
 func (e *Err) Format(s fmt.State, verb rune)
 ```
 Format implements fmt.Formatter
 When printing errors with %+v it also prints the stack trace.
 %#v unsurprisingly will print the real underlying type.


 ### func (\*Err) Location
 ``` go
 func (e *Err) Location() (filename string, line int)
 ```
 Location is the file and line of where the error was most recently
 created or annotated.


 ### func (\*Err) Message
 ``` go
 func (e *Err) Message() string
 ```
 Message returns the message stored with the most recent location. This is
 the empty string if the most recent call was Trace, or the message stored
 with Annotate or Mask.


 ### func (\*Err) SetLocation
 ``` go
 func (e *Err) SetLocation(callDepth int)
 ```
 SetLocation records the source location of the error at callDepth stack
 frames above the call.


 ### func (\*Err) StackTrace
 ``` go
 func (e *Err) StackTrace() []string
 ```
 StackTrace returns one string for each location recorded in the stack of
 errors. The first value is the originating error, with a line for each
 other annotation or tracing of the error.


 ### func (\*Err) Underlying
 ``` go
 func (e *Err) Underlying() error
 ```
 Underlying returns the previous error in the error stack, if any. A client
 should not ever really call this method.  It is used to build the error
 stack and should not be introspected by client calls.  Or more
 specifically, clients should not depend on anything but the `Cause` of an
 error.


 - - -
 Generated by [godoc2md](http://godoc.org/github.com/davecheney/godoc2md)

	# errors
	import "github.com/juju/errors"

	[![GoDoc](https://godoc.org/github.com/juju/errors?status.svg)](https://godoc.org/github.com/juju/errors)

	The juju/errors provides an easy way to annotate errors without losing the
	original error context.

	The exported `New` and `Errorf` functions are designed to replace the
	`errors.New` and `fmt.Errorf` functions respectively. The same underlying
	error is there, but the package also records the location at which the error
	was created.

	A primary use case for this library is to add extra context any time an
	error is returned from a function.


	if err := SomeFunc(); err != nil {
	return err
	}

	This instead becomes:


	if err := SomeFunc(); err != nil {
	return errors.Trace(err)
	}

	which just records the file and line number of the Trace call, or


	if err := SomeFunc(); err != nil {
	return errors.Annotate(err, "more context")
	}

	which also adds an annotation to the error.

	When you want to check to see if an error is of a particular type, a helper
	function is normally exported by the package that returned the error, like the
	`os` package does. The underlying cause of the error is available using the
	`Cause` function.


	os.IsNotExist(errors.Cause(err))

	The result of the `Error()` call on an annotated error is the annotations joined
	with colons, then the result of the `Error()` method for the underlying error
	that was the cause.


	err := errors.Errorf("original")
	err = errors.Annotatef(err, "context")
	err = errors.Annotatef(err, "more context")
	err.Error() -> "more context: context: original"

	Obviously recording the file, line and functions is not very useful if you
	cannot get them back out again.


	errors.ErrorStack(err)

	will return something like:


	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:

	The first error was generated by an external system, so there was no location
	associated. The second, fourth, and last lines were generated with Trace calls,
	and the other two through Annotate.

	Sometimes when responding to an error you want to return a more specific error
	for the situation.


	if err := FindField(field); err != nil {
	return errors.Wrap(err, errors.NotFoundf(field))
	}

	This returns an error where the complete error stack is still available, and
	`errors.Cause()` will return the `NotFound` error.






	## func AlreadyExistsf
	``` go
	func AlreadyExistsf(format string, args ...interface{}) error
	```
	AlreadyExistsf returns an error which satisfies IsAlreadyExists().


	## func Annotate
	``` go
	func Annotate(other error, message string) error
	```
	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 Annotatef
	``` go
	func Annotatef(other error, format string, args ...interface{}) error
	```
	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 BadRequestf
	``` go
	func BadRequestf(format string, args ...interface{}) error
	```
	BadRequestf returns an error which satisfies IsBadRequest().


	## func Cause
	``` go
	func Cause(err error) error
	```
	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 DeferredAnnotatef
	``` go
	func DeferredAnnotatef(err *error, format string, args ...interface{})
	```
	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 Details
	``` go
	func Details(err error) string
	```
	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 ErrorStack
	``` go
	func ErrorStack(err error) string
	```
	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 Errorf
	``` go
	func Errorf(format string, args ...interface{}) error
	```
	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 Forbiddenf
	``` go
	func Forbiddenf(format string, args ...interface{}) error
	```
	Forbiddenf returns an error which satistifes IsForbidden()


	## func IsAlreadyExists
	``` go
	func IsAlreadyExists(err error) bool
	```
	IsAlreadyExists reports whether the error was created with
	AlreadyExistsf() or NewAlreadyExists().


	## func IsBadRequest
	``` go
	func IsBadRequest(err error) bool
	```
	IsBadRequest reports whether err was created with BadRequestf() or
	NewBadRequest().


	## func IsForbidden
	``` go
	func IsForbidden(err error) bool
	```
	IsForbidden reports whether err was created with Forbiddenf() or
	NewForbidden().


	## func IsMethodNotAllowed
	``` go
	func IsMethodNotAllowed(err error) bool
	```
	IsMethodNotAllowed reports whether err was created with MethodNotAllowedf() or
	NewMethodNotAllowed().


	## func IsNotAssigned
	``` go
	func IsNotAssigned(err error) bool
	```
	IsNotAssigned reports whether err was created with NotAssignedf() or
	NewNotAssigned().


	## func IsNotFound
	``` go
	func IsNotFound(err error) bool
	```
	IsNotFound reports whether err was created with NotFoundf() or
	NewNotFound().


	## func IsNotImplemented
	``` go
	func IsNotImplemented(err error) bool
	```
	IsNotImplemented reports whether err was created with
	NotImplementedf() or NewNotImplemented().


	## func IsNotProvisioned
	``` go
	func IsNotProvisioned(err error) bool
	```
	IsNotProvisioned reports whether err was created with NotProvisionedf() or
	NewNotProvisioned().


	## func IsNotSupported
	``` go
	func IsNotSupported(err error) bool
	```
	IsNotSupported reports whether the error was created with
	NotSupportedf() or NewNotSupported().


	## func IsNotValid
	``` go
	func IsNotValid(err error) bool
	```
	IsNotValid reports whether the error was created with NotValidf() or
	NewNotValid().


	## func IsUnauthorized
	``` go
	func IsUnauthorized(err error) bool
	```
	IsUnauthorized reports whether err was created with Unauthorizedf() or
	NewUnauthorized().


	## func IsUserNotFound
	``` go
	func IsUserNotFound(err error) bool
	```
	IsUserNotFound reports whether err was created with UserNotFoundf() or
	NewUserNotFound().


	## func Mask
	``` go
	func Mask(other error) error
	```
	Mask hides the underlying error type, and records the location of the masking.


	## func Maskf
	``` go
	func Maskf(other error, format string, args ...interface{}) error
	```
	Mask 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 MethodNotAllowedf
	``` go
	func MethodNotAllowedf(format string, args ...interface{}) error
	```
	MethodNotAllowedf returns an error which satisfies IsMethodNotAllowed().


	## func New
	``` go
	func New(message string) error
	```
	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 NewAlreadyExists
	``` go
	func NewAlreadyExists(err error, msg string) error
	```
	NewAlreadyExists returns an error which wraps err and satisfies
	IsAlreadyExists().


	## func NewBadRequest
	``` go
	func NewBadRequest(err error, msg string) error
	```
	NewBadRequest returns an error which wraps err that satisfies
	IsBadRequest().


	## func NewForbidden
	``` go
	func NewForbidden(err error, msg string) error
	```
	NewForbidden returns an error which wraps err that satisfies
	IsForbidden().


	## func NewMethodNotAllowed
	``` go
	func NewMethodNotAllowed(err error, msg string) error
	```
	NewMethodNotAllowed returns an error which wraps err that satisfies
	IsMethodNotAllowed().


	## func NewNotAssigned
	``` go
	func NewNotAssigned(err error, msg string) error
	```
	NewNotAssigned returns an error which wraps err that satisfies
	IsNotAssigned().


	## func NewNotFound
	``` go
	func NewNotFound(err error, msg string) error
	```
	NewNotFound returns an error which wraps err that satisfies
	IsNotFound().


	## func NewNotImplemented
	``` go
	func NewNotImplemented(err error, msg string) error
	```
	NewNotImplemented returns an error which wraps err and satisfies
	IsNotImplemented().


	## func NewNotProvisioned
	``` go
	func NewNotProvisioned(err error, msg string) error
	```
	NewNotProvisioned returns an error which wraps err that satisfies
	IsNotProvisioned().


	## func NewNotSupported
	``` go
	func NewNotSupported(err error, msg string) error
	```
	NewNotSupported returns an error which wraps err and satisfies
	IsNotSupported().


	## func NewNotValid
	``` go
	func NewNotValid(err error, msg string) error
	```
	NewNotValid returns an error which wraps err and satisfies IsNotValid().


	## func NewUnauthorized
	``` go
	func NewUnauthorized(err error, msg string) error
	```
	NewUnauthorized returns an error which wraps err and satisfies
	IsUnauthorized().


	## func NewUserNotFound
	``` go
	func NewUserNotFound(err error, msg string) error
	```
	NewUserNotFound returns an error which wraps err and satisfies
	IsUserNotFound().


	## func NotAssignedf
	``` go
	func NotAssignedf(format string, args ...interface{}) error
	```
	NotAssignedf returns an error which satisfies IsNotAssigned().


	## func NotFoundf
	``` go
	func NotFoundf(format string, args ...interface{}) error
	```
	NotFoundf returns an error which satisfies IsNotFound().


	## func NotImplementedf
	``` go
	func NotImplementedf(format string, args ...interface{}) error
	```
	NotImplementedf returns an error which satisfies IsNotImplemented().


	## func NotProvisionedf
	``` go
	func NotProvisionedf(format string, args ...interface{}) error
	```
	NotProvisionedf returns an error which satisfies IsNotProvisioned().


	## func NotSupportedf
	``` go
	func NotSupportedf(format string, args ...interface{}) error
	```
	NotSupportedf returns an error which satisfies IsNotSupported().


	## func NotValidf
	``` go
	func NotValidf(format string, args ...interface{}) error
	```
	NotValidf returns an error which satisfies IsNotValid().


	## func Trace
	``` go
	func Trace(other error) error
	```
	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 Unauthorizedf
	``` go
	func Unauthorizedf(format string, args ...interface{}) error
	```
	Unauthorizedf returns an error which satisfies IsUnauthorized().


	## func UserNotFoundf
	``` go
	func UserNotFoundf(format string, args ...interface{}) error
	```
	UserNotFoundf returns an error which satisfies IsUserNotFound().


	## func Wrap
	``` go
	func Wrap(other, newDescriptive error) error
	```
	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 Wrapf
	``` go
	func Wrapf(other, newDescriptive error, format string, args ...interface{}) error
	```
	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)
	}



	## type Err
	``` go
	type Err struct {
	// contains filtered or unexported fields
	}
	```
	Err holds a description of an error along with information about
	where the error was created.

	It may be embedded in custom error types to add extra information that
	this errors package can understand.









	### func NewErr
	``` go
	func NewErr(format string, args ...interface{}) Err
	```
	NewErr is used to return an Err for the purpose of embedding in other
	structures. The location is not specified, and needs to be set with a call
	to SetLocation.

	For example:


	type FooError struct {
	errors.Err
	code int
	}

	func NewFooError(code int) error {
	err := &FooError{errors.NewErr("foo"), code}
	err.SetLocation(1)
	return err
	}


	### func NewErrWithCause
	``` go
	func NewErrWithCause(other error, format string, args ...interface{}) Err
	```
	NewErrWithCause is used to return an Err with cause by other error for the purpose of embedding in other
	structures. The location is not specified, and needs to be set with a call
	to SetLocation.

	For example:


	type FooError struct {
	errors.Err
	code int
	}

	func (e *FooError) Annotate(format string, args ...interface{}) error {
	err := &FooError{errors.NewErrWithCause(e.Err, format, args...), e.code}
	err.SetLocation(1)
	return err
	})




	### func (\*Err) Cause
	``` go
	func (e *Err) Cause() error
	```
	The Cause of an error is the most recent error in the error stack that
	meets one of these criteria: the original error that was raised; the new
	error that was passed into the Wrap function; the most recently masked
	error; or nil if the error itself is considered the Cause. Normally this
	method is not invoked directly, but instead through the Cause stand alone
	function.



	### func (\*Err) Error
	``` go
	func (e *Err) Error() string
	```
	Error implements error.Error.



	### func (\*Err) Format
	``` go
	func (e *Err) Format(s fmt.State, verb rune)
	```
	Format implements fmt.Formatter
	When printing errors with %+v it also prints the stack trace.
	%#v unsurprisingly will print the real underlying type.



	### func (\*Err) Location
	``` go
	func (e *Err) Location() (filename string, line int)
	```
	Location is the file and line of where the error was most recently
	created or annotated.



	### func (\*Err) Message
	``` go
	func (e *Err) Message() string
	```
	Message returns the message stored with the most recent location. This is
	the empty string if the most recent call was Trace, or the message stored
	with Annotate or Mask.



	### func (\*Err) SetLocation
	``` go
	func (e *Err) SetLocation(callDepth int)
	```
	SetLocation records the source location of the error at callDepth stack
	frames above the call.



	### func (\*Err) StackTrace
	``` go
	func (e *Err) StackTrace() []string
	```
	StackTrace returns one string for each location recorded in the stack of
	errors. The first value is the originating error, with a line for each
	other annotation or tracing of the error.



	### func (\*Err) Underlying
	``` go
	func (e *Err) Underlying() error
	```
	Underlying returns the previous error in the error stack, if any. A client
	should not ever really call this method. It is used to build the error
	stack and should not be introspected by client calls. Or more
	specifically, clients should not depend on anything but the `Cause` of an
	error.









	- - -
	Generated by [godoc2md](http://godoc.org/github.com/davecheney/godoc2md)