factory

Factory linter

The linter checks that the Structures are created by the Factory, and not directly.

The checking helps to provide invariants without exclusion and helps avoid creating an invalid object.

Use

Installation

go install github.com/maranqz/go-factory-lint/cmd/go-factory-lint@latest

Options

• --packageGlobs - list of glob packages, which can create structures without factories inside the glob package. By default, all structures from another package should be created by factories, tests.
  • onlyPackageGlobs - use a factory to initiate a structure for glob packages only, tests.

Example

package main

import (
	"fmt"

	"bad"
)

func main() {
	// Use factory for bad.User
	u := &bad.User{
		ID: -1,
	}

	fmt.Println(u.ID) // -1
	fmt.Println(u.CreatedAt) // time.Time{}
}

package bad

import "time"

type User struct {
	ID        int64
	CreatedAt time.Time
}

var sequenceID = int64(0)

func NextID() int64 {
	sequenceID++

	return sequenceID
}

package main

import (
	"fmt"

	"good"
)

func main() {
	u := good.NewUser()
	
	fmt.Println(u.ID)        // auto increment
	fmt.Println(u.CreatedAt) // time.Now()
}

package user

import "time"

type User struct {
	ID        int64
	CreatedAt time.Time
}

func NewUser() *User {
	return &User{
		ID: nextID(),
		CreatedAt: time.Now(),
	}
}

var sequenceID = int64(0)

func nextID() int64 {
	sequenceID++

	return sequenceID
}

False Negative

Linter doesn't catch some cases.

1. Buffered channel. You can initialize struct in line v, ok := <-bufCh example.
2. Local initialization, example.
3. Named return. If you want to block that case, you can use nonamedreturns linter, example.
4. var declaration, var initilized nested.Struct gives structure without factory, example.

TODO

Possible Features

1. Catch nested struct in the same package, example.

   return Struct{
       Other: OtherStruct{}, // want `Use factory for nested.Struct`
   }
   

2. Resolve false negative issue with var declaration.

Features that are difficult to implement and unplanned

1. Type assertion, type declaration and type underlying, tests.