errors

package module
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README ¶

errors

Package errors provides simple error handling primitives. Migrated from golib.

Based on github.com/pkg/errors, and fully compatible with github.com/pkg/errors.

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Getting Started

Coder
package main

import (
	"fmt"
	"net/http"

	"github.com/shipengqi/errors"
)

type fakeCoder struct {
	code   int
	status int
	msg    string
	ref    string
}

func (d fakeCoder) Code() int         { return d.code }
func (d fakeCoder) String() string    { return d.msg }
func (d fakeCoder) Reference() string { return d.ref }
func (d fakeCoder) HTTPStatus() int {
	if d.status == 0 {
		return http.StatusInternalServerError
	}
	return d.status
}

type parseCoder struct {
	code int
}

func (d parseCoder) Code() int { return d.code }

func main() {
	// annotates err with a code.
	codeErr := errors.WithCode(fmt.Errorf("demo error"), 20010)

	// reports whether any error in err's contains the given code.
	fmt.Println(errors.IsCode(codeErr, 20010)) // true
	
	// returns an error annotating err with a code and a stack trace at the point WrapCodef is called.
	_ = errors.WrapCode(fmt.Errorf("demo error"), 20011)
	// returns an error annotating err with a code and a stack trace at the point WrapCodef is called, and the format specifier.
	_ = errors.WrapCodef(fmt.Errorf("wrap error"), 20012, "wrap %s", "demo")
	

	demoCoder := fakeCoder{
		code:   20013,
		status: http.StatusBadRequest,
		msg:    "bad request",
		ref:    "https://docs.example.com/codes",
	}
	
	// registers a Coder to the global cache.
	errors.Register(demoCoder)
	
	// parse any error into icoder interface, find the corresponding Coder from global cache.
	errors.ParseCoder(parseCoder{code: 20013})
}
Aggregate
package main

import (
	"fmt"
	
	"github.com/shipengqi/errors"
)

func main() {
	// Aggregate represents an object that contains multiple errors, but does not 
	// necessarily have singular semantic meaning
	var errs []error
	errs = append(errs, 
		errors.New("error 1"), 
		errors.New("error 2"), 
		errors.New("error 3"),
	)

	agge := errors.NewAggregate(errs)
	fmt.Println(agge.Error()) // [error 1, error 2, error 3]
}

Documentation

You can find the docs at go docs.

🔋 JetBrains OS licenses

errors had been being developed with GoLand under the free JetBrains Open Source license(s) granted by JetBrains s.r.o., hence I would like to express my thanks here.

JetBrains Logo (Main) logo.

Documentation ¶

Overview ¶

Package errors provides simple error handling primitives.

The traditional error handling idiom in Go is roughly akin to 

if err != nil {
        return err
}

which when applied recursively up the call stack results in error reports without context or debugging information. The errors package allows programmers to add context to the failure path in their code in a way that does not destroy the original value of the error.

Adding context to an error ¶

The e.Wrap function returns a new error that adds context to the original error by recording a stack trace at the point Wrap is called, together with the supplied message. For example 

_, err := ioutil.ReadAll(r)
if err != nil {
        return e.Wrap(err, "read failed")
}

If additional control is required, the e.WithStack and e.WithMessage functions destructure e.Wrap into its component operations: annotating an error with a stack trace and with a message, respectively.

Retrieving the cause of an error ¶

Using e.Wrap constructs a stack of errors, adding context to the preceding error. Depending on the nature of the error it may be necessary to reverse the operation of e.Wrap to retrieve the original error for inspection. Any error value which implements this interface 

type causer interface {
        Cause() error
}

can be inspected by e.Cause. e.Cause will recursively retrieve the topmost error that does not implement causer, which is assumed to be the original cause. For example: 

switch err := e.Cause(err).(type) {
case *MyError:
        // handle specifically
default:
        // unknown error
}

Although the causer interface is not exported by this package, it is considered a part of its stable public interface.

Formatted printing of errors ¶

All error values returned from this package implement fmt.Formatter and can be formatted by the fmt package. The following verbs are supported: 

%s    print the error. If the error has a Cause it will be
      printed recursively.
%v    see %s
%+v   extended format. Each Frame of the error's StackTrace will
      be printed in detail.

Retrieving the stack trace of an error or wrapper ¶

New, Errorf, Wrap, and Wrapf record a stack trace at the point they are invoked. This information can be retrieved with the following interface: 

type stackTracer interface {
        StackTrace() e.StackTrace
}

The returned e.StackTrace type is defined as 

type StackTrace []Frame

The Frame type represents a call site in the stack trace. Frame supports the fmt.Formatter interface that can be used for printing information about the stack trace of this error. For example: 

if err, ok := err.(stackTracer); ok {
        for _, f := range err.StackTrace() {
                fmt.Printf("%+s:%d\n", f, f)
        }
}

Although the stackTracer interface is not exported by this package, it is considered a part of its stable public interface.

See the documentation for Frame.Format for more details.

Example (StackTrace) ¶ 
type stackTracer interface {
	StackTrace() StackTrace
}

err, ok := 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/shipegnqi/errors_test.fn
//	/home/dfc/src/github.com/shipegnqi/errors/example_test.go:47
// github.com/shipegnqi/errors_test.Example_stackTrace
//	/home/dfc/src/github.com/shipegnqi/errors/example_test.go:127

Index ¶

Examples ¶

Constants ¶

This section is empty.

Variables ¶

View Source 
var ErrPreconditionViolated = errors.New("precondition is violated")

ErrPreconditionViolated is returned when the precondition is violated

Functions ¶

func As ¶ 

func As(err error, target interface{}) bool

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 ¶ 

func Cause(err error) error

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 ¶ 
err := fn()
fmt.Println(err)
fmt.Println(Cause(err))

Output:

outer: middle: inner: error
error
Example (Printf) ¶ 
err := Wrap(func() error {
	return func() error {
		return New("hello world")
	}()
}(), "failed")

fmt.Printf("%v", err)

Output:

failed: hello world

func Errorf ¶ 

func Errorf(format string, args ...interface{}) error

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) ¶ 
err := Errorf("whoops: %s", "foo")
fmt.Printf("%+v", err)

// Example Output:
// whoops: foo
// github.com/shipegnqi/errors_test.ExampleErrorf
//         /home/dfc/src/github.com/shipegnqi/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/shipegnqi/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

func FilterOut ¶ added in v0.1.4 

func FilterOut(err error, fns ...Matcher) error

FilterOut removes all errors that match any of the matchers from the input error. If the input is a singular error, only that error is tested. If the input implements the Aggregate interface, the list of errors will be processed recursively.

This can be used, for example, to remove known-OK errors (such as io.EOF or os.PathNotFound) from a list of errors.

func Is ¶ 

func Is(err, target error) bool

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 IsCode ¶ 

func IsCode(err error, code int) bool

IsCode reports whether any error in err's contains the given code.

func Join ¶ added in v0.3.0 

func Join(errs ...error) error

Join returns an error that wraps the given errors. Any nil error values are discarded. Join returns nil if every value in errs is nil. The error formats as the concatenation of the strings obtained by calling the Error method of each element of errs, with a newline between each string.

A non-nil error returned by Join implements the Unwrap() []error method.

For more information see stdlib errors.Join.

func New ¶ 

func New(message string) error

New returns an error with the supplied message. New also records the stack trace at the point it was called.

Example ¶ 
err := New("whoops")
fmt.Println(err)

Output:

whoops
Example (Printf) ¶ 
err := New("whoops")
fmt.Printf("%+v", err)

// Example Output:
// whoops
// github.com/shipegnqi/errors_test.ExampleNew_printf
//         /home/dfc/src/github.com/shipengqi/errors/example_test.go:15
// 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/shipegnqi/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

func Reduce ¶ added in v0.1.4 

func Reduce(err error) error

Reduce will return err or, if err is an Aggregate and only has one item, the first item in the aggregate.

func Register ¶ 

func Register(code Coder)

Register registers an Coder.

func Unwrap ¶ 

func Unwrap(err error) error

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 WithCode ¶ 

func WithCode(err error, code int) error

WithCode annotates err with a code. If err is nil, WithCode returns nil.

Example ¶ 
cause := New("whoops")
err := WithCode(cause, 1)
fmt.Println(err)

Output:

code: 1, whoops

func WithCodef ¶ 

func WithCodef(err error, code int, format string, args ...interface{}) error

WithCodef returns a code error with the format specifier.

Example ¶ 
cause := New("whoops")
err := WithCodef(cause, 1, "oh %s", "noes")
fmt.Println(err)

Output:

code: 1, oh noes: whoops

func WithMessage ¶ 

func WithMessage(err error, message string) error

WithMessage annotates err with a new message. If err is nil, WithMessage returns nil.

Example ¶ 
cause := New("whoops")
err := WithMessage(cause, "oh noes")
fmt.Println(err)

Output:

oh noes: whoops

func WithMessagef ¶ 

func WithMessagef(err error, format string, args ...interface{}) error

WithMessagef annotates err with the format specifier. If err is nil, WithMessagef returns nil.

func WithStack ¶ 

func WithStack(err error) error

WithStack annotates err with a stack trace at the point WithStack was called. If err is nil, WithStack returns nil.

Example ¶ 
cause := New("whoops")
err := WithStack(cause)
fmt.Println(err)

Output:

whoops
Example (Printf) ¶ 
cause := New("whoops")
err := WithStack(cause)
fmt.Printf("%+v", err)

// Example Output:
// whoops
// github.com/shipegnqi/errors_test.ExampleWithStack_printf
//         /home/fabstu/go/src/github.com/shipegnqi/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/shipegnqi/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/shipegnqi/errors_test.ExampleWithStack_printf
//         /home/fabstu/go/src/github.com/shipegnqi/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/shipegnqi/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

func Wrap ¶ 

func Wrap(err error, message string) error

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 ¶ 
cause := New("whoops")
err := Wrap(cause, "oh noes")
fmt.Println(err)

Output:

oh noes: whoops
Example (Extended) ¶ 
err := fn()
fmt.Printf("%+v\n", err)

// Example Output:
// error
// github.com/shipegnqi/errors_test.fn
//         /home/dfc/src/github.com/shipegnqi/errors/example_test.go:47
// github.com/shipegnqi/errors_test.ExampleCause_printf
//         /home/dfc/src/github.com/shipegnqi/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/shipegnqi/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/shipegnqi/errors_test.fn
// 	  /home/dfc/src/github.com/shipegnqi/errors/example_test.go:48: inner
// github.com/shipegnqi/errors_test.fn
//        /home/dfc/src/github.com/shipegnqi/errors/example_test.go:49: middle
// github.com/shipegnqi/errors_test.fn
//      /home/dfc/src/github.com/shipegnqi/errors/example_test.go:50: outer

func WrapCode ¶ added in v0.3.2 

func WrapCode(err error, code int) error

WrapCode returns an error annotating err with a code and a stack trace at the point WrapCode is called. If err is nil, WrapCode returns nil.

Example ¶ 
cause := New("whoops")
err := WrapCode(cause, 1)
fmt.Println(err)

Output:

code: 1, whoops

func WrapCodef ¶ added in v0.3.2 

func WrapCodef(err error, code int, format string, args ...interface{}) error

WrapCodef returns an error annotating err with a code and a stack trace at the point WrapCodef is called, and the format specifier. If err is nil, WrapCodef returns nil.

Example ¶ 
cause := New("whoops")
err := WrapCodef(cause, 1, "oh %s", "noes")
fmt.Println(err)

Output:

code: 1, oh noes: whoops

func Wrapf ¶ 

func Wrapf(err error, format string, args ...interface{}) error

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 ¶ 
cause := New("whoops")
err := Wrapf(cause, "oh noes #%d", 2)
fmt.Println(err)

Output:

oh noes #2: whoops

Types ¶

type Aggregate ¶ added in v0.1.4 

type Aggregate interface {
	error
	Errors() []error
	Is(error) bool
}

Aggregate represents an object that contains multiple errors, but does not necessarily have singular semantic meaning. The aggregate can be used with `errors.Is()` to check for the occurrence of a specific error type. Errors.As() is not supported, because the caller presumably cares about a specific error of potentially multiple that match the given type.

func AggregateGoroutines ¶ added in v0.1.4 

func AggregateGoroutines(funcs ...func() error) Aggregate

AggregateGoroutines runs the provided functions in parallel, stuffing all non-nil errors into the returned Aggregate. Returns nil if all the functions complete successfully.

func CreateAggregateFromMessageCountMap ¶ added in v0.1.4 

func CreateAggregateFromMessageCountMap(m MessageCountMap) Aggregate

CreateAggregateFromMessageCountMap converts MessageCountMap Aggregate

func Flatten ¶ added in v0.1.4 

func Flatten(agg Aggregate) Aggregate

Flatten takes an Aggregate, which may hold other Aggregates in arbitrary nesting, and flattens them all into a single Aggregate, recursively.

func NewAggregate ¶ added in v0.1.4 

func NewAggregate(errlist []error) Aggregate

NewAggregate converts a slice of errors into an Aggregate interface, which is itself an implementation of the error interface. If the slice is empty, this returns nil. It will check if any of the element of input error list is nil, to avoid nil pointer panic when call Error().

Example ¶ 
var errs []error
errs = append(errs,
	errors.New("error 1"),
	errors.New("error 2"),
	errors.New("error 3"),
)

aggregate := NewAggregate(errs)
fmt.Println(aggregate.Error())

Output:

[error 1, error 2, error 3]

type Callers ¶ 

type Callers interface {
	error
	Stack() []uintptr
}

type Coder ¶ added in v0.1.1 

type Coder interface {
	// HTTPStatus that should be used for the associated error code.
	HTTPStatus() int

	// String error message.
	String() string

	// Reference returns the detail documents for user.
	Reference() string
	// contains filtered or unexported methods
}

func ParseCoder ¶ added in v0.1.2 

func ParseCoder(err error) Coder

ParseCoder parse any error into icoder interface. nil error will return nil direct. None withStack error will be parsed as Unknown Code.

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 ¶ 

func (f Frame) Format(s fmt.State, verb rune)

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 ¶ 

func (f Frame) MarshalText() ([]byte, error)

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 Matcher ¶ added in v0.1.4 

type Matcher func(error) bool

Matcher is used to match errors. Returns true if the error matches.

type MessageCountMap ¶ added in v0.1.4 

type MessageCountMap map[string]int

MessageCountMap contains occurrence for each error message.

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 ¶

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Directories ¶

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