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package errors
import (
"errors"
"fmt"
)
var (
_ Definition = definition("")
_ Error = &derivedError{}
)
// BaseError defines a simple error implementation
type BaseError interface {
// Error returns the error string
Error() string
// Is checks whether an error is equal to this one
Is(error) bool
// Unwrap attempts to unwrap any contained errors
Unwrap() error
}
// Definition describes an error implementation that allows creating
// errors derived from this. e.g. global errors defined at runtime
// that are called with `.New()` or `.Wrap()` to derive new errors with
// extra contextual information when needed
type Definition interface {
// New returns a new Error based on Definition using
// supplied string as contextual information
New(a ...interface{}) Error
// Newf returns a new Error based on Definition using
// supplied format string as contextual information
Newf(string, ...interface{}) Error
// Wrap returns a new Error, wrapping supplied error with
// a wrapper with definition as the outer error
Wrap(error) Error
// must implement BaseError
BaseError
}
// Error defines an error implementation that supports wrapping errors, easily
// accessing inner / outer errors in the wrapping structure, and setting extra
// contextual information related to this error
type Error interface {
// Outer returns the outermost error
Outer() error
// Extra allows you to set extra contextual information. Please note
// that multiple calls to .Extra() will overwrite previously set information
Extra(...interface{}) Error
// Extraf allows you to set extra contextual information using a format string.
// Please note that multiple calls to .Extraf() will overwrite previously set
// information
Extraf(string, ...interface{}) Error
// must implement BaseError
BaseError
}
// New returns a simple error implementation. This exists so that `go-errors` can
// be a drop-in replacement for the standard "errors" library
func New(msg string) error {
return definition(msg)
}
// Define returns a new error Definition
func Define(msg string) Definition {
return definition(msg)
}
// Wrap wraps the supplied inner error within a struct of the outer error
func Wrap(outer, inner error) Error {
// If this is a wrapped error but inner is nil, use this
if derived, ok := outer.(*derivedError); ok && derived.inner == nil {
derived.inner = inner
return derived
}
// Create new derived error
return &derivedError{
msg: "",
extra: "",
outer: outer,
inner: inner,
}
}
type definition string
func (e definition) New(a ...interface{}) Error {
return &derivedError{
msg: fmt.Sprint(a...),
extra: "",
inner: nil,
outer: e,
}
}
func (e definition) Newf(msg string, a ...interface{}) Error {
return &derivedError{
msg: fmt.Sprintf(msg, a...),
extra: "",
inner: nil,
outer: e,
}
}
func (e definition) Wrap(err error) Error {
return &derivedError{
msg: "",
extra: "",
inner: err,
outer: e,
}
}
func (e definition) Error() string {
return string(e)
}
func (e definition) Is(err error) bool {
switch err := err.(type) {
case definition:
return e == err
case *derivedError:
return err.Is(e)
default:
return false
}
}
func (e definition) Unwrap() error {
return nil
}
type derivedError struct {
msg string // msg provides the set message for this derived error
extra string // extra provides any extra set contextual information
inner error // inner is the error being wrapped
outer error // outer is the outmost error in this wrapper
}
func (e *derivedError) Error() string {
// Error starts with outer error
s := e.outer.Error() + ` (`
// Add any message
if e.msg != "" {
s += `msg="` + e.msg + `" `
}
// Add any wrapped error
if e.inner != nil {
s += `wrapped="` + e.inner.Error() + `" `
}
// Add any extra information
if e.extra != "" {
s += `extra="` + e.extra + `" `
}
// Return error string
return s[:len(s)-1] + `)`
}
func (e *derivedError) Is(err error) bool {
return errors.Is(e.outer, err) || errors.Is(e.inner, err)
}
func (e *derivedError) Outer() error {
return e.outer
}
func (e *derivedError) Unwrap() error {
return e.inner
}
func (e *derivedError) Extra(a ...interface{}) Error {
e.extra = fmt.Sprint(a...)
return e
}
func (e *derivedError) Extraf(s string, a ...interface{}) Error {
e.extra = fmt.Sprintf(s, a...)
return e
}
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