generr

README

generr

generate error utilities for golang.

Inspired by BANZAI CLOUD's Error Handling Practices in Go, this command generate custom error utilities from simple interface declaration.

Getting Started

Prerequisites

• Go 1.11+
• make

Installing

$ go get -u github.com/akito0107/generr/cmd/generr

How to use

1. You declare interface which must have a single function and named return values (if needs).

type userNotFound interface {
	UserNotFound() (id int64)
}

1. Generate implementation with passing the type name.

$ generr -t userNotFound

1. Then, you can get implementation file which named userNotFound_check.go. This file contains the function which identifies whether given error is the one that we are defined before.

func IsUserNotFound(err error) (bool, int64) {
	var id int64
	if e, ok := err.(userNotFound); ok {
		id = e.UserNotFound()
		return true, id
	}
	return false, id
}

1. You can also generate struct which implements error and the interface with -i option.

$ generr -t userNotFound -i -it userNotFound -o ../otherpackage

You get generated file named userNotFound_impl.go.

package otherpackage

type userNotFound struct {
	Id int64
}

func (e *userNotFound) UserNotFound() int64 {
	return e.Id
}
func (e *userNotFound) Error() string {
	return fmt.Sprintf("userNotFound Id: %v", e.Id)
}

You can pass struct name with -it option (default case is capitalized name given with -t). -o option (default location is current directory and package).

1. You can unify check and impl files with -u option.

$ generr -t userNotFound -i -u

func IsUserNotFound(err error) (bool, int64) {
	var id int64
	if e, ok := err.(userNotFound); ok {
		id = e.UserNotFound()
		return true, id
	}
	return false, id
}

type UserNotFound struct {
	Id int64
}

func (e *UserNotFound) UserNotFound() int64 {
	return e.Id
}
func (e *UserNotFound) Error() string {
	return fmt.Sprintf("userNotFound Id: %v", e.Id)
}

1. You can also use go generate

//go:generate generr -t notFound -i -u
type userNotFound interface {
	UserNotFound() (id int64)
}

$ go generate // you can get same results.

1. You can pass custom error message with -m flag.

//go:generate generr -t emailNotFound -m "email %s not found" -i -u
type emailNotFound interface{
    EmailNotFound() (email string)	
}

and run go generate

$ go generate 

then, you get custom error utilities with passed error message.

// Code generated by "generr"; DO NOT EDIT.
package e2e

import "fmt"

func IsEmailNotFound(err error) (bool, string) {
	var email string
	if e, ok := err.(emailNotFound); ok {
		email = e.EmailNotFound()
		return true, email
	}
	return false, email
}

type EmailNotFound struct {
	Email string
}

func (e *EmailNotFound) EmailNotFound() string {
	return e.Email
}
func (e *EmailNotFound) Error() string {
	return fmt.Sprintf("email %s is not found", e.Email)
}

Options

$ generr -h
NAME:
   generr - generate custom error from interface

USAGE:
   generr [OPTIONS]

VERSION:
   0.0.0

COMMANDS:
     help, h  Shows a list of commands or help for one command

GLOBAL OPTIONS:
   --type value, -t value                        error interface name (required)
   --dryrun                                      dryrun (default=false)
   --implementation, -i                          generate error implementation (default=false)
   --unify, -u                                   (only affects with --implementation option) unify implementation with checking function (default=false)
   --implementation-output-path value, -o value  (only affects with --implementation option) implementation output path (default=current directory)
   --implementation-type value, --it value       (only affects with --implementation option) implementation type name (default=capitalized given type name)
   --message value, -m value                     custom error message (optional)
   --cause, -c                                   append cause check (default=false)
   --help, -h                                    show help
   --version, -v                                 print the version

License

This project is licensed under the Apache License 2.0 License - see the LICENSE file for details

Documentation

Overview

Code generated by "generr"; DO NOT EDIT.

Index

• func IsTypeNotFound(err error) bool
• func Parse(r io.Reader, tp string) (string, *ast.TypeSpec, error)
• type Generator
  • func NewGenerator(pkgName string, ts *ast.TypeSpec) *Generator
  • func (g *Generator) AppendCheckFunction(withCause bool) error
  • func (g *Generator) AppendErrorImplementation(typename, message string) error
  • func (g *Generator) AppendPackage()
  • func (g *Generator) AppendPkgErrorImportSpec()
  • func (g *Generator) Generate() error
  • func (g *Generator) Out(w io.Writer) error
• type TypeNotFound
  • func (e *TypeNotFound) Error() string
  • func (e *TypeNotFound) TypeNotFound()

Functions

func IsTypeNotFound

func IsTypeNotFound(err error) bool

func Parse

func Parse(r io.Reader, tp string) (string, *ast.TypeSpec, error)

Types

type Generator

type Generator struct {
	// contains filtered or unexported fields
}

func NewGenerator

func NewGenerator(pkgName string, ts *ast.TypeSpec) *Generator

func (*Generator) AppendCheckFunction

func (g *Generator) AppendCheckFunction(withCause bool) error

func (*Generator) AppendErrorImplementation

func (g *Generator) AppendErrorImplementation(typename, message string) error

func (*Generator) AppendPackage

func (g *Generator) AppendPackage()

func (*Generator) AppendPkgErrorImportSpec

func (g *Generator) AppendPkgErrorImportSpec()

func (*Generator) Generate

func (g *Generator) Generate() error

func (*Generator) Out

func (g *Generator) Out(w io.Writer) error

type TypeNotFound

type TypeNotFound struct {
}

func (*TypeNotFound) Error

func (e *TypeNotFound) Error() string

func (*TypeNotFound) TypeNotFound

func (e *TypeNotFound) TypeNotFound()