Pre-fill domain block/allow domain from search filter (#18172)

app/javascript/packs/admin.js

@@ -100,6 +100,16 @@ ready(() => {
   const registrationMode = document.getElementById('form_admin_settings_registrations_mode');
   if (registrationMode) onChangeRegistrationMode(registrationMode);
 
+  document.querySelector('a#add-instance-button')?.addEventListener('click', (e) => {
+    const domain = document.getElementById('by_domain')?.value;
+
+    if (domain) {
+      const url = new URL(event.target.href);
+      url.searchParams.set('_domain', domain);
+      e.target.href = url;
+    }
+  });
+
   const React    = require('react');
   const ReactDOM = require('react-dom');
 

app/views/admin/instances/index.html.haml

@@ -1,11 +1,14 @@
 - content_for :page_title do
   = t('admin.instances.title')
 
+- content_for :header_tags do
+  = javascript_pack_tag 'admin', async: true, crossorigin: 'anonymous'
+
 - content_for :heading_actions do
   - if whitelist_mode?
-    = link_to t('admin.domain_allows.add_new'), new_admin_domain_allow_path, class: 'button'
+    = link_to t('admin.domain_allows.add_new'), new_admin_domain_allow_path, class: 'button', id: 'add-instance-button'
   - else
-    = link_to t('admin.domain_blocks.add_new'), new_admin_domain_block_path, class: 'button'
+    = link_to t('admin.domain_blocks.add_new'), new_admin_domain_block_path, class: 'button', id: 'add-instance-button'
 
 .filters
   .filter-subset