Option to report struct errors based on json field name about govalidator HOT 14 OPEN

@asaskevich sure, I'll try and do it over the weekend 😃

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We wanted the same thing, we ended up using reflect to get the validation subject struct fields, extract their json tags to get the field name we want to return in responses, something like this:

func ValidationError(ctx echo.Context, s interface{}, err error) error {
    switch err.(type) {
    case govalidator.Errors:
        // Use reflect to get the raw struct element
        typ := reflect.TypeOf(s).Elem()
        if typ.Kind() != reflect.Struct {
            return UnexpectedError(ctx, errors.New("validation subject is not a struct"))
        }

        // This is will contain the errors we return back to user
        errs := map[string]string{}
        // Errors found by the validator
        errsByField := govalidator.ErrorsByField(err.(govalidator.Errors))
        // Loop over our struct fields
        for i := 0; i < typ.NumField(); i++ {
            // Get the field
            f := typ.Field(i)
            // Do we have an error for the field
            e, ok := errsByField[f.Name]
            if ok {
                // Try and get the `json` struct tag
                name := strings.Split(f.Tag.Get("json"), ",")[0]
                // If the name is - we should ignore the field
                if name == "-" {
                    continue
                }
                // If the name is not blank we add it our error map
                if name != "" {
                    errs[name] = e
                    continue
                }
                // Finall if all else has failed just add the raw field name to the
                // error map
                errs[f.Name] = e
            }
        }

        // Return the validation error
        mapper := &Errors{Message: "Validation Error", Errors: errs}
        return ErrorHandler(422, mapper, ctx)
    }

    // If the error type is not a govalidator.Errors, return a 500
    return UnexpectedError(
        ctx,
        fmt.Errorf("Expected govalidator.Errors, got %s", reflect.TypeOf(err)))
}

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@krak3n could you put your example into pull request with sample of usage and small note in docs please?

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+1!!!!

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If the intent is make the messages more user friendly I think that would be better use a field for these only purpose.

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Hmmm i see your point and in some ways it is more flexible. But also the the json tag is what the user will practically see for any restful JSON applications, which I believe will be a alot of use cases.

Could we potentially have some way of specifying a custom tag field?

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Looking forward to this PR.

Is it just going to use the json:"value" as it's field name, or perhaps different approach will be taken?

Thanks.

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@paroxp I didn't get to it last weekend but hopefully this weekend, it's just going to be documentation how how you could use reflection to get the json, xml or what ever other struct tag to get the field name you want to use for the error value.

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do we have updates or solution?

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What about nested field names?

If we validate the following, we get Name: invalid_alphanum does not validate as alphanum. However, we cannot identify which failed when nested fields contain the same name.

type Resource struct {
    Name string `json:"name" valid:"alphanum"`
    Version string `json:"version" valid:"required"`
    Env struct {
        Name string `json:"name" valid:"alphanum"`
        Value string `json:"value" valid:"required"`
    }
}

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@retr0h it should return something like Env.Name: invalid_alphanum does not validate as alphanum or Env.name ...?

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^ Yes, that would be the expected behavior, however is not the case currently

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@asaskevich *

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Hello guys!
I forked this package cause owner disappeared. Hope, he will be back, but it would be easier to merge these changes back if he is back
Link to my repo: create issue there and we'll discuss it.

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