Input Validation Get JSON tags

[hmajid2301]

Hi I know you've already provided me with a lot of help.
I have another question, I know this might not be directly related to Fizz, however I cannot seem to
work out how to get it working with Fizz/Tonic. However others can get it work with Gin directly.

It is around input validation errors, I know validators is used to check the incoming data. So if I do

curl -X POST http://localhost:8080/game  -H "Content-Type: application/json" -d "{\"name\":\"quibly\",\"ruls_url\":\"https://gitlab.com/banter-bus/games\"}"

# Output
{
    "message": "binding error: Key: 'NewGame.RulesURL' Error:Field validation for 'RulesURL' failed on the 'required' tag"
}

Where the expected data is modelled like:

type NewGame struct {
	Name     string `json:"name"      validate:"required"`
	RulesURL string `json:"rules_url" validate:"required"`
}

I would like to use just get the json field names i.e. rules_url and create my own error message to return back to the client.

for _, err := range e.(tonic.BindError).ValidationErrors() {
	fmt.Println(err.Namespace())
	fmt.Println(err.Field())
	fmt.Println(err.StructNamespace())
	fmt.Println(err.StructField())
	fmt.Println(err.Tag())
	fmt.Println(err.ActualTag())
	fmt.Println(err.Kind())
	fmt.Println(err.Type())
	fmt.Println(err.Value())
	fmt.Println(err.Param())
	fmt.Println()
}

Which outputs:

NewGame.RulesURL
RulesURL
NewGame.RulesURL
RulesURL
required
required
string
string

I've tried to add a custom validator to gin as Validators maintainer suggests here

	binding.Validator = new(defaultValidator)
	
        engine := gin.New()
	engine.Use(cors.Default())
	fizzApp := fizz.NewFromEngine(engine)

       // ....
	infos := &openapi.Info{
		Title:       "Banter Bus",
		Description: "The API definition for the Banter Bus server.",
		Version:     "1.0.0",
	}

Where the defaultValidator looks like:

import (
	"reflect"
	"strings"
	"sync"

	"github.com/gin-gonic/gin/binding"
	"github.com/go-playground/validator/v10"
)

type defaultValidator struct {
	once     sync.Once
	validate *validator.Validate
}

var _ binding.StructValidator = &defaultValidator{}

func (v *defaultValidator) ValidateStruct(obj interface{}) error {

	if kindOfData(obj) == reflect.Struct {

		v.lazyinit()

		if err := v.validate.Struct(obj); err != nil {
			return err
		}
	}

	return nil
}

func (v *defaultValidator) Engine() interface{} {
	v.lazyinit()
	return v.validate
}

func (v *defaultValidator) lazyinit() {
	v.once.Do(func() {
		v.validate = validator.New()
		v.validate.SetTagName("binding") // Print JSON name on validator.FieldError.Field()
		v.validate.RegisterTagNameFunc(func(fld reflect.StructField) string {
			name := strings.SplitN(fld.Tag.Get("json"), ",", 2)[0]
			return name
		})
	})
}

func kindOfData(data interface{}) reflect.Kind {

	value := reflect.ValueOf(data)
	valueType := value.Kind()

	if valueType == reflect.Ptr {
		valueType = value.Elem().Kind()
	}
	return valueType
}

I was wondering if you could suggest a way I could get the JSON tag (`rules_url) from the struct rather than the struct field name(RulesURL). I've tried debugging it myself with breakpoints but I cannot seem to work it out. Any help would be appreciated thanks.

P.S. Sorry for the information overload.

[hmajid2301]

Ok further investigation this is an issue with tonic:

in the handler.go

If update initValidator() to

func initValidator() {
	validatorOnce.Do(func() {
		validatorObj = validator.New()
		validatorObj.SetTagName(ValidationTag)
		validatorObj.RegisterTagNameFunc(func(fld reflect.StructField) string {
			name := strings.SplitN(fld.Tag.Get("json"), ",", 2)[0]
			if name == "-" {
				return ""
			}
			return name
		})
	})
}

fmt.Println(err.Field()) returns rules_url which is the JSON struct tag.