NEW SearchableDropdownField

lang/en.yml

@@ -141,6 +141,10 @@ en:
     IsNullLabel: 'Is Null'
   SilverStripe\Forms\NumericField:
     VALIDATION: "'{value}' is not a number, only numbers can be accepted for this field"
+  SilverStripe\Forms\SearchableDropdownTrait:
+    SELECT: 'Select...'
+    TYPE_TO_SEARCH: 'Type to search...'
+    SELECT_OR_TYPE_TO_SEARCH: 'Select or type to search...'
   SilverStripe\Forms\TextField:
     VALIDATEMAXLENGTH: 'The value for {name} must not exceed {maxLength} characters in length'
   SilverStripe\Forms\TimeField:

src/Forms/SearchableDropdownField.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace SilverStripe\Forms;
+
+use SilverStripe\Dev\Deprecation;
+use SilverStripe\Forms\DropdownField;
+use SilverStripe\ORM\DataList;
+
+class SearchableDropdownField extends DropdownField
+{
+    use SearchableDropdownTrait;
+
+    // This needs to be defined on the class, not the trait, otherwise there is a PHP error
+    protected $schemaComponent = 'SearchableDropdownField';
+
+    public function __construct(
+        string $name,
+        string $title,
+        DataList $source,
+        mixed $value = null,
+        string $labelField = 'Title'
+    ) {
+        parent::__construct($name, $title, $source, $value);
+        $this->setLabelField($labelField);
+        $this->addExtraClass('ss-searchable-dropdown-field');
+        $this->setHasEmptyDefault(true);
+    }
+
+    /**
+     * @param string $string
+     * @return $this
+     *
+     * @deprecated 5.2.0 Use setPlaceholder() instead
+     */
+    public function setEmptyString($string)
+    {
+        Deprecation::notice('5.2.0', 'Use setPlaceholder() instead');
+        return parent::setEmptyString($string);
+    }
+}