Validation Error Translator

Intrroduction

Validation error translator is a package that translate github.com/go-playground/validator error into human readable error based on the validation tag.
ex: tag required will be translated to The field cannot be empty.

Instalation

Use go get.

go get github.com/mproyyan/validation-error-translator

Usage

package main

import (
   "fmt"

   "github.com/go-playground/validator/v10"
   tl "github.com/mproyyan/validation-error-translator"
)

type Sample struct {
   Name  string   `validate:"required"`
   Num   int      `validate:"lte=100"`
}

func main() {
   // load translation
   tl.Load("en")

   validation := validator.New()
   s := Sample{
      Name: "",
      Num:  200,
   }

   err := validation.Struct(s)
   if err != nil {
      for _, field := range err.(validator.ValidationErrors) {
         errTl := tl.Translate(field)
         fmt.Prinln(errTl)
      }
   }
}

Result

The Name cannot be empty.
The Num must be less than or equal to 100.

Load from file

This package support to load translation from your own file, make sure file is json format

// indonesian translation id.json

{
   "required": "Field :f tidak boleh kosong.",
   "lte": {
      "item": "Field :f harus kurang dari atau sama dengan :p item.",
      "string": "Field :f harus kurang dari atau sama dengan :p karakter.",
      "numeric": "Field :f harus kurang dari atau sama dengan :p."
   }
}

func main() {
   file, _ := os.Open("path-to-your-file/id.json")
   defer file.Close()

   tl.LoadFromFile(file)
}

Placeholder

Raw string translation that contains placeholder will be replaced with actual data, data obtained from validator.FieldError interface, you can see here for the detail.

Placeholder list

• :f replaced with (validator.FieldError).Field()
• :p replaced with (validator.FieldError).Param()
• :t replaced with (validator.FieldError).Tag()
• :at replaced with (validator.FieldError).ActualTag()
• :n replaced with (validator.FieldError).Namespace()
• :sn replaced with (validator.FieldError).StructNamespace()
• :sf replaced with (validator.FieldError).StructField()

Rules adding new translations

1. Translation must be string cannot be int nor array

   {
      "required": 1342, // invalid
      "required": ["test", 123], // invalid
      "required": "The :f cannot be empty." // valid
   }

2. Value of nested translation must be string cannot be int, array nor other nested translation and must have these three child (item, string, numeric)

   {
      // invalid
      "len": {
         "item": 123,
         "string": [123, "test"],
         "numeric": {
            "invalid": "invalid"
         }
      },
   
      // valid
      "len": {
         "item": "The :f must have :p items.",
         "string": "The :f must be :p characters in length.",
         "numeric": "The :f must be equal to :p."
      }
   }

Adding translation

Adding or replace single translation

// adding test to translations
tl.AddTranslation("test", "this is just test", false)

// replace required translation
tl.AddTranslation("required", "replaced", true)

Adding or replace batch of translations

// you can use map[string]any or tl.M
// tl.M is shorthand for map[string]any
newTranslations := tl.M{
   "test": "just test",
   "test2": "another test",
}

// adding translations
tl.AddTranslations(newTranslations, false)

replaceTranslations := map[string]any{
   "required": "replaced",
   "len": tl.M{
      "item": "replaced",
      "string": "replaced",
      "numeric": "replaced",
   },
}

// replace translations
tl.AddTranslations(replaceTranslations, true)