README
¶
errors
This package is a fork from github.com/pkg/errors package created by Dave Cheney. The original package has no longer accepting proposals for new functionality.
With the new errors on go 1.13, the way to using the errors on Go has some changes that can be applied into Dave Cheney library. We want to offer one way to migrate your code to new errors, but with the minimum refactor, for that we've created this package.
This package provide the same interface that the original library have, but using new go 1.13 errors, or in previous version golang.org/x/xerrors package.
How to start using friendsofgo/errors
If you previously was using the package github.com/pkg/errors, you only need
change your imports for github.com/friendsofgo/errors, with this simple change now you're capable to use
go 1.13 in your code, and use the new methods As and Is if you want.
Furthermore the method Wrap Wrapf become compatible with Unwrap` interface of new go 1.13 errors.
Adding context to an error
With the original package go 1.13 if you want add context, ergo wrap your error you need to create a new error and using the new verb `"%w" like that:
_, err := ioutil.ReadAll(r)
if err != nil {
return fmt.Errorf("read failed: %w", err)
}
Using our library you can do that forgetting to the new verb:
_, err := ioutil.ReadAll(r)
if err != nil {
return errors.Wrap(err, "read failed")
}
Retrieving the cause of an error
We want to keep the compatibility with the github.com/pkg/errors package, for that
our package provides a Cause method, but this method is not longer needed, because we can use the new methods Is or As
that provides the official package.
So previously if you needed to check an error cause, your error must be implemented the causer inteface:
type causer interface {
Cause() error
}
errors.Cause will recursively retrieve the topmost error which 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
}
But now you can do:
var target *MyError
if errors.As(err, &target) {
// handle specifically
} else {
// unknown error
}
Or if you uses a sentinel error:
var ErrMyError = errors.New("my sentinel error")
if errors.Is(err, ErrMyError) {
// handle specifically
} else {
// unknown error
}
Disclaimer
This package was created to using with go 1.13 version however if you uses this package with a previous version, the methods
As, Is, Wrap and Wrapf will be using golang.org/x/xerrors package.
Contributing
Contributions are more than welcome, if you are interested please fork this repo and send your Pull Request.
Documentation
¶
Overview ¶
Example (StackTrace) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func fn() error {
e1 := errors.New("error")
e2 := errors.Wrap(e1, "inner")
e3 := errors.Wrap(e2, "middle")
return errors.Wrap(e3, "outer")
}
func main() {
type stackTracer interface {
StackTrace() errors.StackTrace
}
err, ok := errors.Cause(fn()).(stackTracer)
if !ok {
panic("oops, err does not implement stackTracer")
}
st := err.StackTrace()
fmt.Printf("%+v", st[0:2]) // top two frames
// Example output:
// github.com/friendsofgo/errors_test.fn
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:47
// github.com/friendsofgo/errors_test.Example_stackTrace
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:127
}
Output:
Index ¶
- func As(err error, target interface{}) bool
- func Cause(err error) error
- func Errorf(format string, args ...interface{}) error
- func FormatPanicDebugStack(msg string) string
- func Is(err error, target error) bool
- func New(message string) error
- func WithMessage(err error, message string) error
- func WithMessagef(err error, format string, args ...interface{}) error
- func WithStack(err error) error
- func Wrap(err error, message string) error
- func Wrapf(err error, format string, args ...interface{}) error
- type Frame
- type StackTrace
Examples ¶
Constants ¶
This section is empty.
Variables ¶
This section is empty.
Functions ¶
func As ¶
As finds the first error in err's chain that matches target, and if so, sets target to that error value and returns true.
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(interface{}) bool such that As(target) returns true. In the latter case, the As method is responsible for setting target.
As will panic if target is not a non-nil pointer to either a type that implements error, or to any interface type. As returns false if err is nil.
func Cause ¶
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.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func fn() error {
e1 := errors.New("error")
e2 := errors.Wrap(e1, "inner")
e3 := errors.Wrap(e2, "middle")
return errors.Wrap(e3, "outer")
}
func main() {
err := fn()
fmt.Println(err)
fmt.Println(errors.Cause(err))
}
Output: outer: middle: inner: error error
Example (Printf) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
err := errors.Wrap(func() error {
return func() error {
return errors.Errorf("hello %s", fmt.Sprintf("world"))
}()
}(), "failed")
fmt.Printf("%v", err)
}
Output: failed: hello world
func Errorf ¶
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.
Example (Extended) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
err := errors.Errorf("whoops: %s", "foo")
fmt.Printf("%+v", err)
// Example output:
// whoops: foo
// github.com/friendsofgo/errors_test.ExampleErrorf
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:101
// testing.runExample
// /home/dfc/go/src/testing/example.go:114
// testing.RunExamples
// /home/dfc/go/src/testing/example.go:38
// testing.(*M).Run
// /home/dfc/go/src/testing/testing.go:744
// main.main
// /github.com/friendsofgo/errors/_test/_testmain.go:102
// runtime.main
// /home/dfc/go/src/runtime/proc.go:183
// runtime.goexit
// /home/dfc/go/src/runtime/asm_amd64.s:2059
}
Output:
func FormatPanicDebugStack ¶
func Is ¶
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.
func New ¶
New returns an error with the supplied message. New also records the stack trace at the point it was called.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
err := errors.New("whoops")
fmt.Println(err)
}
Output: whoops
Example (Printf) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
err := errors.New("whoops")
fmt.Printf("%+v", err)
// Example output:
// whoops
// github.com/friendsofgo/errors_test.ExampleNew_printf
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:17
// testing.runExample
// /home/dfc/go/src/testing/example.go:114
// testing.RunExamples
// /home/dfc/go/src/testing/example.go:38
// testing.(*M).Run
// /home/dfc/go/src/testing/testing.go:744
// main.main
// /github.com/friendsofgo/errors/_test/_testmain.go:106
// runtime.main
// /home/dfc/go/src/runtime/proc.go:183
// runtime.goexit
// /home/dfc/go/src/runtime/asm_amd64.s:2059
}
Output:
func WithMessage ¶
WithMessage annotates err with a new message. If err is nil, WithMessage returns nil.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
cause := errors.New("whoops")
err := errors.WithMessage(cause, "oh noes")
fmt.Println(err)
}
Output: oh noes: whoops
func WithMessagef ¶
WithMessagef annotates err with the format specifier. If err is nil, WithMessagef returns nil.
func WithStack ¶
WithStack annotates err with a stack trace at the point WithStack was called. If err is nil, WithStack returns nil.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
cause := errors.New("whoops")
err := errors.WithStack(cause)
fmt.Println(err)
}
Output: whoops
Example (Printf) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
cause := errors.New("whoops")
err := errors.WithStack(cause)
fmt.Printf("%+v", err)
// Example Output:
// whoops
// github.com/friendsofgo/errors_test.ExampleWithStack_printf
// /home/fabstu/go/src/github.com/friendsofgo/errors/example_test.go:55
// testing.runExample
// /usr/lib/go/src/testing/example.go:114
// testing.RunExamples
// /usr/lib/go/src/testing/example.go:38
// testing.(*M).Run
// /usr/lib/go/src/testing/testing.go:744
// main.main
// github.com/friendsofgo/errors/_test/_testmain.go:106
// runtime.main
// /usr/lib/go/src/runtime/proc.go:183
// runtime.goexit
// /usr/lib/go/src/runtime/asm_amd64.s:2086
// github.com/friendsofgo/errors_test.ExampleWithStack_printf
// /home/fabstu/go/src/github.com/friendsofgo/errors/example_test.go:56
// testing.runExample
// /usr/lib/go/src/testing/example.go:114
// testing.RunExamples
// /usr/lib/go/src/testing/example.go:38
// testing.(*M).Run
// /usr/lib/go/src/testing/testing.go:744
// main.main
// github.com/friendsofgo/errors/_test/_testmain.go:106
// runtime.main
// /usr/lib/go/src/runtime/proc.go:183
// runtime.goexit
// /usr/lib/go/src/runtime/asm_amd64.s:2086
}
Output:
func Wrap ¶
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.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
cause := errors.New("whoops")
err := errors.Wrap(cause, "oh noes")
fmt.Println(err)
}
Output: oh noes: whoops
Example (Extended) ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func fn() error {
e1 := errors.New("error")
e2 := errors.Wrap(e1, "inner")
e3 := errors.Wrap(e2, "middle")
return errors.Wrap(e3, "outer")
}
func main() {
err := fn()
fmt.Printf("%+v\n", err)
// Example output:
// error
// github.com/friendsofgo/errors_test.fn
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:47
// github.com/friendsofgo/errors_test.ExampleCause_printf
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:63
// testing.runExample
// /home/dfc/go/src/testing/example.go:114
// testing.RunExamples
// /home/dfc/go/src/testing/example.go:38
// testing.(*M).Run
// /home/dfc/go/src/testing/testing.go:744
// main.main
// /github.com/friendsofgo/errors/_test/_testmain.go:104
// runtime.main
// /home/dfc/go/src/runtime/proc.go:183
// runtime.goexit
// /home/dfc/go/src/runtime/asm_amd64.s:2059
// github.com/friendsofgo/errors_test.fn
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:48: inner
// github.com/friendsofgo/errors_test.fn
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:49: middle
// github.com/friendsofgo/errors_test.fn
// /home/dfc/src/github.com/friendsofgo/errors/example_test.go:50: outer
}
Output:
func Wrapf ¶
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.
Example ¶
package main
import (
"fmt"
"git.bit5.ru/backend/errors"
)
func main() {
cause := errors.New("whoops")
err := errors.Wrapf(cause, "oh noes #%d", 2)
fmt.Println(err)
}
Output: oh noes #2: whoops
Types ¶
type Frame ¶
type Frame uintptr
Frame represents a program counter inside a stack frame. For historical reasons if Frame is interpreted as a uintptr its value represents the program counter + 1.
func (Frame) Format ¶
Format formats the frame according to the fmt.Formatter interface.
%s source file %d source line %n function name %v equivalent to %s:%d
Format accepts flags that alter the printing of some verbs, as follows:
%+s function name and path of source file relative to the compile time
GOPATH separated by \n\t (<funcname>\n\t<path>)
%+v equivalent to %+s:%d
func (Frame) MarshalText ¶
MarshalText formats a stacktrace Frame as a text string. The output is the same as that of fmt.Sprintf("%+v", f), but without newlines or tabs.
type StackTrace ¶
type StackTrace []Frame
StackTrace is stack of Frames from innermost (newest) to outermost (oldest).
func (StackTrace) Format ¶
func (st StackTrace) Format(s fmt.State, verb rune)
Format formats the stack of Frames according to the fmt.Formatter interface.
%s lists source files for each Frame in the stack %v lists the source file and line number for each Frame in the stack
Format accepts flags that alter the printing of some verbs, as follows:
%+v Prints filename, function, and line number for each Frame in the stack.
Source Files