Kenshō - A Go validator

A Work in progress project so the master branch might change in the future and BC breaks some part or change some behaviors.

A simple Go library for validation, but gives the possibility to validate deeply, collections, any field type of struct by following tag or file.

TODO

• More docs/examples
• More tests
• Add validators

Features

• Struct validation
• Able to add custom constraints
• Validator argument
• Configuration from a file (ex: json)
• Deep validation
• List of struct validation
• Translation

Installation

go get github.com/maxperrimond/kensho

Usage

Here some code as an example:

package main

import (
	"fmt"

	"github.com/maxperrimond/kensho"
)

type Group struct {
	Name  string  `valid:"required"`
	Users []*User `valid:"valid"` // Ask to valid users if there is some
}

type User struct {
	Email     string `valid:"required,email"`
	FirstName string `valid:"required,min=2,max=64"`
	LastName  string `valid:"required,min=2,max=64"`
}

func main() {
	// Simple struct
	user := &User{
		Email:     "foo.bar@example.com",
		FirstName: "foo",
		LastName:  "bar",
	}

	// Validate user
	ok, violations, _ := kensho.Validate(user)

	fmt.Printf("Result: %t\n", ok)
	fmt.Println(violations)

	user.Email = "this is not an email"
	user.FirstName = ""

	// Validate user after inserting bad data
	ok, violations, _ = kensho.Validate(user)

	fmt.Printf("Result: %t\n", ok)
	fmt.Println(violations)

	users := []*User{
		{
			Email:     "john@example.com",
			FirstName: "john",
			LastName:  "bar",
		},
		{
			Email:     "pierre@example.com",
			FirstName: "pierre",
			LastName:  "bar",
		},
	}

	// Validate collection of users
	ok, violations, _ = kensho.Validate(users)

	fmt.Printf("Result: %t\n", ok)
	fmt.Println(violations)

	// Nested struct
	group := &Group{
		Name:  "foo",
		Users: append(users, user), // With the bad user
	}

	// Validate the group
	ok, violations, _ = kensho.Validate(group)

	fmt.Printf("Result: %t\n", ok)
	fmt.Println(violations)
}

Available constraints

Tag	Arg	Description
valid		Validate nested struct
string		Check is string
struct		Check is struct
required		Is required
length	int	Match length
min	int	Match min length
max	int	Match max length
regex	string (regex pattern)	Match pattern
email		Match email
uuid		Match UUID
iso3166	optional: num, alpha3, alpha2 (default)	Match country code based on IS03166

And more to come

Custom constraint

package main

import (
	"context"
	"errors"

	"github.com/maxperrimond/kensho"
)

// Define your constraint
func poneyConstraint(ctx *kensho.ValidationContext) error {
	if ctx.Value() != "poney" {
		ctx.BuildViolation("invalid_poney", nil).AddViolation()
	}

	return nil
}

func init() {
	// add it with the tag of your choice
    kensho.AddConstraint("poney", poneyConstraint)
}

Note: If you use an existent tag, it will override it.

Context

You can pass a context during validation so it can be accessible in constraints:

ok, violations, err := kensho.ValidateWithContext(ctx, subject)