vee-validate validation message not working in Laravel 5.6.7 - vue.js

Question

I am using Laravel 5.6.7 with vue.js for form validation. I have successfully installed using npm install vee-validate#next --save
<form role="form">
<select name="Role_ID" v-validate data-vv-rules="required">
<option :value="-1" selected>Please select Role</option>
<option v-for="RoleRecord in RoleRecords" :value="RoleRecord.Role_ID">
{{RoleRecord.Role}}
</option>
</select>
<p v-if="errors.has('Role_ID')">{{ errors.first('Role_ID') }}</p>
<!-- UserName -->
<div>
<label>UserName</label>
<div class="col-md-9">
<input name="User Name" v-validate data-vv-rules="required" type="text"
v-model="createForm.UserName">
<p v-if="errors.has('User Name')">{{ errors.first('User Name') }}</p>
</div>
</div>
<button type="button" #click="validateBeforeSubmit()">
Save Changes
</button>
</form>
<script>
export default {
methods: {
validateBeforeSubmit() {
this.$validator.validateAll();
}
}
}
</script>
My findings
Due to some reasons the option is not being validated.
There is UserName field which is working perfectly.
I am expecting that it should show the error message if the option selected value is less then 0
Am I missing anything? Please let me know if you need more info.

Answer 1

in the vee-validate doc,
The field under validation must have a non-empty value. By default,
all validators pass the validation if they have "empty values" unless
they are required. Those empty values are: empty strings, undefined,
null.
-1 is still considered a valid value for required validation. Use specified empty values instead. (Namely: empty strings, undefined, null)
e.g.
<option :value="null" selected>Please select Role</option>
This should trigger the required validation.
Example: https://codepen.io/jacobgoh101/pen/geaqwr?editors=1011

Answer 2

There's a difference between your naming:
<input name="User Name" v-validate data-vv-rules="required" type="text" v-model="createForm.UserName">
<p v-if="errors.has('User Name')">{{ errors.first('User Name') }}</p>
v-model uses UserName (without spacing). The name-attribute in your input and errors.has + errors.first are using User Name (with spacing). Please make sure you're naming things exactly the same, both in front-end as well as in back-end (and preferably without whitespace).