Go playground url validate

Question

I am sending a request which has a URL and Content in the body. The validations are such that either URL or epicentre is mandatory. The program is erroring when the URL is empty as url validate on an empty string is failing.

Is there a way to run url validate on URL only if its non empty?

Heres my code snippet.

func (d *Doc) UnmarshalJSON(bytearray []byte) error {
    type doc struct {
        ID           ID      `json:"id" validate:"omitempty,numeric"`
        URL          string  `json:"url" validate:"required_without=Content,url"`
        Content      string  `json:"content" validate:"required_without=Url"`
    
    }
    var d doc
    if err := json.Unmarshal(bytearray, &d); err != nil {
        return err
    }
}

Answer 1

There was a similar question raised as an issue within the repo and the suggestion was to use struct level validation.

Example usage within validator examples: https://github.com/go-playground/validator/blob/v9/_examples/struct-level/main.go#L48

The following is untested but should be a good starting point:

import (
    "json"
    "gopkg.in/go-playground/validator.v9"
)

func init() {
    validate.RegisterStructValidation(DocStructLevelValidation, doc{})
}

type doc struct {
    ID           ID      `json:"id" validate:"omitempty,numeric"`
    URL          string  `json:"url"`
    Content      string  `json:"content"`
}

func DocStructLevelValidation(sl validator.StructLevel) {
    d := sl.Current().Interface().(doc)

    if d.URL == "" && d.Content == "" {
        sl.ReportError(d.URL, "url", "URL", "urlcontentrequired", "")
        sl.ReportError(d.Content, "content", "Content", "urlcontentrequired", "")
    }
}

func (d *Doc) UnmarshalJSON(bytearray []byte) error {
    var d doc
    if err := json.Unmarshal(bytearray, &d); err != nil {
        return err
    }
}