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errors.go
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errors.go
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package errors
import (
"encoding/json"
"errors"
"fmt"
"path/filepath"
"reflect"
"runtime"
)
var (
// The function used to encode errors and their tags.
Encoder func(any) ([]byte, error)
)
func init() {
SetInlineEncoder()
}
// SetInlineEncoder is a helper function that set the error encoder to
// json.Marshal.
func SetInlineEncoder() {
Encoder = json.Marshal
}
// SetIndentEncoder is a helper function that set the error encoder to a
// function that uses json.MarshalIndent.
func SetIndentEncoder() {
Encoder = func(v any) ([]byte, error) {
return json.MarshalIndent(v, "", " ")
}
}
// Unwrap returns the result of calling the Unwrap method on err, if err's type
// contains an Unwrap method returning error.
// Otherwise, Unwrap returns nil.
func Unwrap(err error) error {
return errors.Unwrap(err)
}
// Is reports whether any error in err's chain matches target.
//
// The chain consists of err itself followed by the sequence of errors obtained
// by repeatedly calling Unwrap.
//
// An error is considered to match a target if it is equal to that target or if
// it implements a method Is(error) bool such that Is(target) returns true.
//
// An error type might provide an Is method so it can be treated as equivalent
// to an existing error. For example, if MyError defines
//
// func (m MyError) Is(target error) bool { return target == fs.ErrExist }
//
// then Is(MyError{}, fs.ErrExist) returns true. See syscall.Errno.Is for an
// example in the standard library. An Is method should only shallowly compare
// err and the target and not call Unwrap on either.
func Is(err, target error) bool {
return errors.Is(err, target)
}
// As finds the first error in err's chain that matches target, and if one is
// found, sets target to that error value and returns true. Otherwise, it
// returns false.
//
// The chain consists of err itself followed by the sequence of errors obtained
// by repeatedly calling Unwrap.
//
// An error matches target if the error's concrete value is assignable to the
// value pointed to by target, or if the error has a method As(any) bool
// such that As(target) returns true. In the latter case, the As method is
// responsible for setting target.
//
// An error type might provide an As method so it can be treated as if it were a
// different error type.
//
// As panics if target is not a non-nil pointer to either a type that implements
// error, or to any interface type.
func As(err error, target any) bool {
return errors.As(err, target)
}
// Type returns the type of the error.
//
// Uses reflect.TypeOf() when the given error does not implements the Error
// interface.
func Type(err error) string {
if err == nil {
return ""
}
if err, ok := err.(interface{ Type() string }); ok {
return err.Type()
}
return reflect.TypeOf(err).String()
}
// HasType reports whether any error in err's chain matches the given type.
//
// The chain consists of err itself followed by the sequence of errors obtained
// by repeatedly calling Unwrap.
//
// An error matches the given type if the error has a method Type() string such
// that Type() returns a string equal to the given type.
func HasType(err error, v string) bool {
for {
if v == Type(err) {
return true
}
if err = Unwrap(err); err == nil {
return false
}
}
}
// Tag returns the first tag value in err's chain that matches the given key.
//
// The chain consists of err itself followed by the sequence of errors obtained
// by repeatedly calling Unwrap.
//
// An error has a tag when it has a method Tag(string) string such that Tag(k)
// returns a non-empty string value.
func Tag(err error, k string) any {
for {
if err, ok := err.(Error); ok {
if v := err.Tag(k); v != nil {
return v
}
}
if err = Unwrap(err); err == nil {
return nil
}
}
}
// An enriched error.
type Error struct {
Line string
Message string
DefinedType string
Tags map[string]any
WrappedErr error
}
// New returns an error with the given message that can be enriched with a type
// and tags.
func New(msg string) Error {
return makeError(msg)
}
// Newf returns an error with the given formatted message that can be enriched
// with a type and tags.
func Newf(msgFormat string, v ...any) Error {
return makeError(msgFormat, v...)
}
func makeError(msgFormat string, v ...any) Error {
_, filename, line, _ := runtime.Caller(2)
err := Error{
Line: fmt.Sprintf("%s:%v", filepath.Base(filename), line),
Message: fmt.Sprintf(msgFormat, v...),
}
return err
}
func (e Error) WithType(v string) Error {
e.DefinedType = v
return e
}
func (e Error) Type() string {
if e.DefinedType != "" {
return e.DefinedType
}
if e.WrappedErr != nil {
return Type(e.WrappedErr)
}
return reflect.TypeOf(e).String()
}
func (e Error) WithTag(k string, v any) Error {
if e.Tags == nil {
e.Tags = make(map[string]any)
}
e.Tags[k] = v
return e
}
func (e Error) Tag(k string) any {
return e.Tags[k]
}
func (e Error) Wrap(err error) Error {
e.WrappedErr = err
return e
}
func (e Error) Unwrap() error {
return e.WrappedErr
}
func (e Error) Error() string {
s, err := Encoder(e)
if err != nil {
return fmt.Sprintf(`{"message": "encoding error failed: %s"}`, err)
}
return string(s)
}
func (e Error) MarshalJSON() ([]byte, error) {
var wrappedErr any = e.WrappedErr
if _, ok := e.WrappedErr.(Error); !ok && e.WrappedErr != nil {
wrappedErr = e.WrappedErr.Error()
}
var tags map[string]any
if l := len(e.Tags); l != 0 {
tags = make(map[string]any, l)
for k, v := range e.Tags {
switch v := v.(type) {
case reflect.Type:
tags[k] = v.String()
default:
tags[k] = v
}
}
}
return Encoder(struct {
Line string `json:"line,omitempty"`
Message string `json:"message"`
DefinedType string `json:"type,omitempty"`
Tags map[string]any `json:"tags,omitempty"`
WrappedErr any `json:"wrap,omitempty"`
}{
Line: e.Line,
Message: e.Message,
DefinedType: e.DefinedType,
Tags: tags,
WrappedErr: wrappedErr,
})
}
func (e Error) Is(err error) bool {
rerr, ok := err.(Error)
if !ok {
return false
}
return rerr.Line == e.Line &&
rerr.Message == e.Message &&
rerr.DefinedType == e.DefinedType &&
reflect.DeepEqual(rerr.Tags, e.Tags) &&
rerr.WrappedErr == e.WrappedErr
}