Bootstrap and Select2 form validation

Question

Explanation

I'm trying to use Bootstrap's form validation with Select2's select boxes, but for some reason, it doesn't work properly. It does show this feedback text, but not the green/red border color, as you can see in the code below.

Codes

You can also see it in this JSFiddle.

$(".select").select2({
  minimumResultsForSearch: Infinity
});

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" rel="stylesheet" />
<link href="https://rawgit.com/select2/select2/master/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js"></script>
<script src="https://rawgit.com/select2/select2/master/dist/js/select2.js"></script>
<form class="was-validated">

  <div class="form-group">
    <select class="custom-select" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

  <div class="form-group">
    <select class="select custom-select" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

</form>

Thanks in advance,
Luiz.

Answer 1

You need to apply css for override and select2 generate dynamic select so

.was-validated .custom-select:invalid + .select2 .select2-selection{
    border-color: #dc3545!important;
}
.was-validated .custom-select:valid + .select2 .select2-selection{
    border-color: #28a745!important;
}
*:focus{
  outline:0px;
}

$(".select").select2({
  minimumResultsForSearch: Infinity
});

.was-validated .custom-select:invalid + .select2 .select2-selection{
    border-color: #dc3545!important;
}
.was-validated .custom-select:valid + .select2 .select2-selection{
    border-color: #28a745!important;
}
*:focus{
  outline:0px;
}

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" rel="stylesheet" />
<link href="https://rawgit.com/select2/select2/master/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js"></script>
<script src="https://rawgit.com/select2/select2/master/dist/js/select2.js"></script>
<form class="was-validated">

  <div class="form-group">
    <select class="custom-select" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

  <div class="form-group">
    <select class="select custom-select" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

</form>

Answer 2

try this

$(".select").select2({
  minimumResultsForSearch: Infinity
});

<link href="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/css/bootstrap.min.css" rel="stylesheet" />
<link href="https://rawgit.com/select2/select2/master/dist/css/select2.min.css" rel="stylesheet" />
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<script src="https://cdnjs.cloudflare.com/ajax/libs/popper.js/1.14.6/umd/popper.min.js"></script>
<script src="https://stackpath.bootstrapcdn.com/bootstrap/4.2.1/js/bootstrap.min.js"></script>
<script src="https://rawgit.com/select2/select2/master/dist/js/select2.js"></script>
<form class="was-validated">

  <div class="form-group">
    <select class="form-control select2" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

  <div class="form-group">
    <select class="form-control select2" required>
      <option value="">Open this select menu</option>
      <option value="1">One</option>
      <option value="2">Two</option>
      <option value="3">Three</option>
    </select>
    <div class="invalid-feedback">Example invalid custom select feedback</div>
  </div>

</form>