BEF plugin fails when Dropdown is selected for term filters
>>> [!note] Migrated issue
<!-- Drupal.org comment -->
<!-- Migrated from issue #3563218. -->
Reported by: [plopesc](https://www.drupal.org/user/282415)
Related to !187
>>>
<h3 id="summary-problem-motivation">Problem/Motivation</h3>
<p>Tagify BEF plugin works great for term filters, showing a nice widget when the Selection type used in the Filter configuration is set to "Autocomplete".</p>
<p>However, when the Selection type is set to "Dropdown", the view fails, and the log reports the following messages:</p>
<pre> 8 15/Dec 07:59 php Error Drupal\Component\Plugin\Exception\PluginNotFoundException: The "" entity type does not exist. in Drupal\Core\Entity\EntityTypeManager->getDefinition() (line 142 of /var/www/html/docroot/co <br> 7 15/Dec 07:59 php Warning Warning: Undefined array key "#tags" in Drupal\tagify\Plugin\better_exposed_filters\filter\Tagify->exposedFormAlter() (line 83 of /var/www/html/docroot/modules/contrib/tagify/src/Plugin/be <br> 6 15/Dec 07:59 php Warning Warning: Undefined array key "#target_type" in Drupal\tagify\Plugin\better_exposed_filters\filter\Tagify->exposedFormAlter() (line 82 of /var/www/html/docroot/modules/contrib/tagify/src/Pl</pre><p>This is because the dropdown widget does not provide the necessary variables to build the Tagify widget.</p>
<h4 id="summary-steps-reproduce">Steps to reproduce</h4>
<ol>
<li>Install BEF and Tagify modules</li>
<li>Create a View that exposed a filter to a taxonomy term field</li>
<li>In the filter configuration Select "Autocomplete" as the Selection Type</li>
<li>Configure BEF for the filter above and set Tagify as the BEF plugin</li>
<li>Save the view</li>
<li>Exposed filter works as expected</li>
<li>Modify the filter configuration to use "Dropdown" as the Selection Type</li>
<li>Save the view</li>
<li>Confirm that a PHP error is thrown and the view cannot recover from it</li>
</ol>
<h3 id="summary-proposed-resolution">Proposed resolution</h3>
<ul>
<li>Implement isApplicable method to ensure that Tagify plugin is available if only Autocomplete is the option chosen for terms</li>
<li>Add a security clause in the code to fail gracefully if for any reason the form element cannot be configured properly.</li>
</ul>
<h3 id="summary-remaining-tasks">Remaining tasks</h3>
<h3 id="summary-ui-changes">User interface changes</h3>
<h3 id="summary-api-changes">API changes</h3>
<h3 id="summary-data-model-changes">Data model changes</h3>
> Related issue: [Issue #3539738](https://www.drupal.org/node/3539738)
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