Binding with Omitempty and min or gte does not honour '0' case

[raybog]

Description

Binding error when using omitempty along with gte or min when gte=1 or min=1 and parmaeter is 0.

How to reproduce

package main

import (
    "net/http"

    "github.com/gin-gonic/gin"
    "github.com/gin-gonic/gin/binding"
)

type Test struct {
    Test int `form:"test" binding:"omitempty,lte=10,gte=1"`
    Test2 int `form:"test2" binding:"omitempty,max=10,min=1"`
}

func main() {
    route := gin.Default()

    route.GET("/test", getTest)
    route.Run(":8085")
}

func getTest(c *gin.Context) {
    var t Test
    if err := c.ShouldBindWith(&t, binding.Query); err == nil {
        c.JSON(http.StatusOK, gin.H{"message": "Test is valid!"})
    } else {
        c.JSON(http.StatusBadRequest, gin.H{"error": err.Error()})
    }
}

Expectations

$ curl "localhost:8085/test?test=0&test2=0"
{"error":"Key: 'Test.Test' Error:Field validation for 'Test' failed on the 'gte' tag\nKey: 'Test.Test2' Error:Field validation for 'Test2' failed on the 'max' tag"}

Actual result

$ curl "localhost:8085/test?test=0&test2=0"
{"message":"Test is valid!"}

Environment

• go version: go1.14.6 darwin/amd64
• gin version (or commit ref): v1.6.3
• operating system: macOs 10.15.6 (19G73)

[unbyte]

0 is treated as nil value and validators are ignored due to omiempty

[PhantomX7]

you should use pointer for that, because of omitempty behavior

this is on the documentation:

Omit Empty Allows conditional validation, for example if a field is not set with a value (Determined by the "required" validator) then other validation such as min or max won't run, but if a value is set validation will run.

Required This validates that the value is not the data types default zero value. For numbers ensures value is not zero. For strings ensures value is not "". For slices, maps, pointers, interfaces, channels and functions ensures the value is not nil.

In your case, you use int where it's default value is 0, so omitempty will be triggered if it is 0.