brucechen7/failure

failure is a utility package for handling application errors.

failure

Package failure provides an error represented as error code and extensible error interface with wrappers.

Use error code instead of error type.

var NotFound failure.StringCode = "NotFound"

err := failure.New(NotFound)

if failure.Is(err, NotFound) { // true
	r.WriteHeader(http.StatusNotFound)
}

Wrap errors.

type Wrapper interface {
	WrapError(err error) error
}

err := failure.Wrap(err, MarkTemporary())

Unwrap errors with Iterator.

type Unwrapper interface {
	UnwrapError() error
}

i := failure.NewIterator(err)
for i.Next() { // unwrap error
	err := i.Error()
	if e, ok := err.(Temporary); ok {
		return e.IsTemporary()
	}
}

Example

You can try it on The Go Playground

You can also see the example on GitHub by opening this.

package main

import (
	"fmt"
	"io"
	"net/http"
	"net/http/httptest"
	"net/http/httputil"

	"github.com/morikuni/failure"
)

// error codes for your application.
const (
	NotFound  failure.StringCode = "NotFound"
	Forbidden failure.StringCode = "Forbidden"
)

func GetACL(projectID, userID string) (acl interface{}, e error) {
	notFound := true
	if notFound {
		return nil, failure.New(NotFound,
			failure.Context{"project_id": projectID, "user_id": userID},
		)
	}
	return nil, failure.Unexpected("unexpected error")
}

func GetProject(projectID, userID string) (project interface{}, e error) {
	_, err := GetACL(projectID, userID)
	if err != nil {
		// 是找不到的错误码
		if failure.Is(err, NotFound) {
			return nil, failure.Translate(err, Forbidden,
				failure.Message("no acl exists"),
				failure.Context{"additional_info": "hello"},
			)
		}
		// 包裹错误
		return nil, failure.Wrap(err)
	}
	return nil, nil
}

func Handler(w http.ResponseWriter, r *http.Request) {
	_, err := GetProject(r.FormValue("project_id"), r.FormValue("user_id"))
	if err != nil {
		HandleError(w, err)
		return
	}
}

func getHTTPStatus(err error) int {
	c, ok := failure.CodeOf(err)
	if !ok {
		return http.StatusInternalServerError
	}
	switch c {
    // 404
	case NotFound:
		return http.StatusNotFound
	// 403
	case Forbidden:
		return http.StatusForbidden
    // 502
	default:
		return http.StatusInternalServerError
	}
}

func getMessage(err error) string {
	msg, ok := failure.MessageOf(err)
	if ok {
		return msg
	}
	return "Error"
}

func HandleError(w http.ResponseWriter, err error) {
	// 写状态码
	w.WriteHeader(getHTTPStatus(err))
	io.WriteString(w, getMessage(err))

	fmt.Println("============ Error ============")
	fmt.Printf("Error = %v\n", err)

	code, _ := failure.CodeOf(err)
	fmt.Printf("Code = %v\n", code)

	msg, _ := failure.MessageOf(err)
	fmt.Printf("Message = %v\n", msg)

	cs, _ := failure.CallStackOf(err)
	fmt.Printf("CallStack = %v\n", cs)

	fmt.Printf("Cause = %v\n", failure.CauseOf(err))

	fmt.Println()
	fmt.Println("============ Detail ============")
	fmt.Printf("%+v\n", err)
	// [main.GetProject] /go/src/github.com/morikuni/failure/example/main.go:36
	//     message("no acl exists")
	//     additional_info = hello
	//     code(Forbidden)
	// [main.GetACL] /go/src/github.com/morikuni/failure/example/main.go:21
	//     project_id = 123
	//     user_id = 456
	//     code(NotFound)
	// [CallStack]
	//     [main.GetACL] /go/src/github.com/morikuni/failure/example/main.go:21
	//     [main.GetProject] /go/src/github.com/morikuni/failure/example/main.go:33
	//     [main.Handler] /go/src/github.com/morikuni/failure/example/main.go:47
	//     [http.HandlerFunc.ServeHTTP] /usr/local/go/src/net/http/server.go:1964
	//     [http.(*ServeMux).ServeHTTP] /usr/local/go/src/net/http/server.go:2361
	//     [http.serverHandler.ServeHTTP] /usr/local/go/src/net/http/server.go:2741
	//     [http.(*conn).serve] /usr/local/go/src/net/http/server.go:1847
	//     [runtime.goexit] /usr/local/go/src/runtime/asm_amd64.s:1333
}

func main() {
	req := httptest.NewRequest(http.MethodGet, "/?project_id=aaa&user_id=111", nil)
	rec := httptest.NewRecorder()
	Handler(rec, req)

	res, _ := httputil.DumpResponse(rec.Result(), true)
	fmt.Println("============ Dump ============")
	fmt.Println(string(res))
}