gin/binding/default_validator.go

// Copyright 2017 Manu Martinez-Almeida.  All rights reserved.
// Use of this source code is governed by a MIT style
// license that can be found in the LICENSE file.

package binding

import (
	"fmt"
	"reflect"
	"sync"

	"github.com/go-playground/validator/v10"
)

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

// SliceFieldError is returned for invalid slice or array elements.
// It extends validator.FieldError with the index of the failing element.
type SliceFieldError interface {
	validator.FieldError
	Index() int
}

type sliceFieldError struct {
	validator.FieldError
	index int
}

func (fe sliceFieldError) Index() int {
	return fe.index
}

func (fe sliceFieldError) Error() string {
	return fmt.Sprintf("[%d]: %s", fe.index, fe.FieldError.Error())
}

func (fe sliceFieldError) Unwrap() error {
	return fe.FieldError
}

var _ StructValidator = &defaultValidator{}

// ValidateStruct receives any kind of type, but validates only structs, pointers, slices, and arrays.
func (v *defaultValidator) ValidateStruct(obj interface{}) error {
	if obj == nil {
		return nil
	}

	value := reflect.ValueOf(obj)
	switch value.Kind() {
	case reflect.Ptr:
		return v.ValidateStruct(value.Elem().Interface())
	case reflect.Struct:
		return v.validateStruct(obj)
	case reflect.Slice, reflect.Array:
		count := value.Len()
		var errs validator.ValidationErrors
		for i := 0; i < count; i++ {
			if err := v.ValidateStruct(value.Index(i).Interface()); err != nil {
				for _, fieldError := range err.(validator.ValidationErrors) { // nolint: errorlint
					errs = append(errs, sliceFieldError{fieldError, i})
				}
			}
		}
		if len(errs) > 0 {
			return errs
		}
		return nil
	default:
		return nil
	}
}

// validateStruct receives struct type
func (v *defaultValidator) validateStruct(obj interface{}) error {
	v.lazyinit()
	return v.validate.Struct(obj)
}

// Engine returns the underlying validator engine which powers the default
// Validator instance. This is useful if you want to register custom validations
// or struct level validations. See validator GoDoc for more info -
// https://pkg.go.dev/github.com/go-playground/validator/v10
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")
	})
}