Hi,

When importing only b-alert, if the dismissed prop is set like this:

<template>
  <b-alert :show="true" :dismissible="true">Message</b-alert>
</template>
<script>
  import bAlert from "bootstrap-vue/es/components/alert/alert";
  export default {
    name: 'Dummy',
    components: {
        bAlert
    }
}

An error is throwed :

[Vue warn]: Unknown custom element: - did you register the component correctly? For recursive components, make sure to provide the "name" option.

This is because the button si imported as bBtnClose (from button/button) and used with b-button-close.