From 06a2b10b4730d3bf2c79eeb883c958537ca76b05 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 09:58:50 +0200
Subject: [PATCH 1/9] provide method to create html options

---
 src/Forms/SelectField.php | 33 +++++++++++++++++++++++++++++++++
 1 file changed, 33 insertions(+)

diff --git a/src/Forms/SelectField.php b/src/Forms/SelectField.php
index edc3f4f0401..6ea7531081e 100644
--- a/src/Forms/SelectField.php
+++ b/src/Forms/SelectField.php
@@ -5,12 +5,16 @@
 use SilverStripe\ORM\SS_List;
 use SilverStripe\ORM\Map;
 use ArrayAccess;
+use SilverStripe\Core\Convert;
 
 /**
  * Represents a field that allows users to select one or more items from a list
  */
 abstract class SelectField extends FormField
 {
+    private static $casting = [
+        'OptionsHTML' => 'HTMLFragment',
+    ];
 
     /**
      * Associative or numeric array of all dropdown items,
@@ -271,4 +275,33 @@ public function castedCopy($classOrCopy)
         }
         return $field;
     }
+
+    /**
+     * Provides <option> list for the template
+     * This allows for a faster rendering of dropdowns with lots of options
+     *
+     * @return string
+     */
+    public function OptionsHTML(): string
+    {
+        // Some methods only exists for single selects
+        $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
+        $emptyString = $this->hasMethod('getEmptyString') ? $this->getEmptyString() : '';
+
+        $currentValue = $this->Value();
+        foreach ($source as $value => $title) {
+            $selected = '';
+            if ($this->isSelectedValue($value, $currentValue)) {
+                $selected = ' selected';
+            }
+            $disabled = '';
+            if ($this->isDisabledValue($value) && $title != $emptyString) {
+                $disabled = ' disabled';
+            }
+            $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
+            $options[] = $item;
+        }
+
+        return implode("\n", $options);
+    }
 }

From 162cadf91976b3ddd771c7c96609a435420e3aa1 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 10:00:02 +0200
Subject: [PATCH 2/9] use OptionsHTML

---
 templates/SilverStripe/Forms/DropdownField.ss | 8 +-------
 1 file changed, 1 insertion(+), 7 deletions(-)

diff --git a/templates/SilverStripe/Forms/DropdownField.ss b/templates/SilverStripe/Forms/DropdownField.ss
index da566e5b5b8..29d8f8ef54c 100644
--- a/templates/SilverStripe/Forms/DropdownField.ss
+++ b/templates/SilverStripe/Forms/DropdownField.ss
@@ -1,9 +1,3 @@
 <select $AttributesHTML>
-<% loop $Options %>
-	<option value="$Value.XML"
-		<% if $Selected %> selected="selected"<% end_if %>
-		<% if $Disabled %> disabled="disabled"<% end_if %>
-		><% if $Title.exists %>$Title.XML<% else %>&nbsp;<% end_if %>
-	</option>
-<% end_loop %>
+$OptionsHTML
 </select>

From 33990f569cf62d745e375d2f7141874e3ea28029 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 11:33:05 +0200
Subject: [PATCH 3/9] use full attributes

---
 src/Forms/SelectField.php | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/Forms/SelectField.php b/src/Forms/SelectField.php
index 6ea7531081e..5fa4fcef35d 100644
--- a/src/Forms/SelectField.php
+++ b/src/Forms/SelectField.php
@@ -292,16 +292,16 @@ public function OptionsHTML(): string
         foreach ($source as $value => $title) {
             $selected = '';
             if ($this->isSelectedValue($value, $currentValue)) {
-                $selected = ' selected';
+                $selected = ' selected="selected"';
             }
             $disabled = '';
             if ($this->isDisabledValue($value) && $title != $emptyString) {
-                $disabled = ' disabled';
+                $disabled = ' disabled="disabled"';
             }
             $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
             $options[] = $item;
         }
-
+        
         return implode("\n", $options);
     }
 }

From 1454aab96e0d401de8d4717fa137183da796b5a5 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 14:25:04 +0200
Subject: [PATCH 4/9] prevent template caching

---
 src/Forms/DropdownField.php | 393 ++++++++++++++++++++++++++----------
 1 file changed, 282 insertions(+), 111 deletions(-)

diff --git a/src/Forms/DropdownField.php b/src/Forms/DropdownField.php
index 765b8a9df31..10db5f65820 100644
--- a/src/Forms/DropdownField.php
+++ b/src/Forms/DropdownField.php
@@ -2,145 +2,316 @@
 
 namespace SilverStripe\Forms;
 
-use SilverStripe\ORM\ArrayList;
-use SilverStripe\View\ArrayData;
+use ArrayAccess;
+use SilverStripe\ORM\Map;
+use SilverStripe\ORM\SS_List;
+use SilverStripe\Core\Convert;
+use SilverStripe\ORM\FieldType\DBHTMLText;
 
 /**
- * Dropdown field, created from a select tag.
- *
- * <b>Setting a $has_one relation</b>
- *
- * Using here an example of an art gallery, with Exhibition pages,
- * each of which has a Gallery they belong to.  The Gallery class is also user-defined.
- * <code>
- *  static $has_one = array(
- *      'Gallery' => 'Gallery',
- *  );
- *
- *  public function getCMSFields() {
- *      $fields = parent::getCMSFields();
- *      $field = DropdownField::create('GalleryID', 'Gallery', Gallery::get()->map('ID', 'Title'))
- *          ->setEmptyString('(Select one)');
- *      $fields->addFieldToTab('Root.Content', $field, 'Content');
- * </code>
- *
- * As you see, you need to put "GalleryID", rather than "Gallery" here.
- *
- * <b>Populate with Array</b>
- *
- * Example model definition:
- * <code>
- * class MyObject extends DataObject {
- *   static $db = array(
- *     'Country' => "Varchar(100)"
- *   );
- * }
- * </code>
- *
- * Example instantiation:
- * <code>
- * DropdownField::create(
- *   'Country',
- *   'Country',
- *   array(
- *     'NZ' => 'New Zealand',
- *     'US' => 'United States',
- *     'GEM'=> 'Germany'
- *   )
- * );
- * </code>
- *
- * <b>Populate with Enum-Values</b>
- *
- * You can automatically create a map of possible values from an {@link Enum} database column.
- *
- * Example model definition:
- * <code>
- * class MyObject extends DataObject {
- *   static $db = array(
- *     'Country' => "Enum('New Zealand,United States,Germany','New Zealand')"
- *   );
- * }
- * </code>
- *
- * Field construction:
- * <code>
- * DropdownField::create(
- *   'Country',
- *   'Country',
- *   singleton('MyObject')->dbObject('Country')->enumValues()
- * );
- * </code>
- *
- * <b>Disabling individual items</b>
- *
- * Individual items can be disabled by feeding their array keys to setDisabledItems.
- *
- * <code>
- * $DrDownField->setDisabledItems( array( 'US', 'GEM' ) );
- * </code>
- *
- * @see CheckboxSetField for multiple selections through checkboxes instead.
- * @see ListboxField for a single <select> box (with single or multiple selections).
- * @see TreeDropdownField for a rich and customizeable UI that can visualize a tree of selectable elements
+ * Represents a field that allows users to select one or more items from a list
  */
-class DropdownField extends SingleSelectField
+abstract class SelectField extends FormField
 {
+    /**
+     * Associative or numeric array of all dropdown items,
+     * with array key as the submitted field value, and the array value as a
+     * natural language description shown in the interface element.
+     *
+     * @var array|ArrayAccess
+     */
+    protected $source;
 
     /**
-     * Build a field option for template rendering
+     * The values for items that should be disabled (greyed out) in the dropdown.
+     * This is a non-associative array
      *
-     * @param mixed $value Value of the option
-     * @param string $title Title of the option
-     * @return ArrayData Field option
+     * @var array
      */
-    protected function getFieldOption($value, $title)
-    {
-        // Check selection
-        $selected = $this->isSelectedValue($value, $this->Value());
+    protected $disabledItems = [];
 
-        // Check disabled
-        $disabled = false;
-        if ($this->isDisabledValue($value) && $title != $this->getEmptyString()) {
-            $disabled = 'disabled';
+    /**
+     * @param string $name The field name
+     * @param string $title The field title
+     * @param array|ArrayAccess $source A map of the dropdown items
+     * @param mixed $value The current value
+     */
+    public function __construct($name, $title = null, $source = [], $value = null)
+    {
+        $this->setSource($source);
+        if (!isset($title)) {
+            $title = $name;
         }
+        parent::__construct($name, $title, $value);
+    }
 
-        return new ArrayData([
-            'Title' => (string)$title,
-            'Value' => $value,
-            'Selected' => $selected,
-            'Disabled' => $disabled,
-        ]);
+    public function getSchemaStateDefaults()
+    {
+        $data = parent::getSchemaStateDefaults();
+        $disabled = $this->getDisabledItems();
+
+        // Add options to 'data'
+        $source = $this->getSource();
+        $data['source'] = (is_array($source))
+            ? array_map(function ($value, $title) use ($disabled) {
+                return [
+                    'value' => $value,
+                    'title' => $title,
+                    'disabled' => in_array($value, $disabled),
+                ];
+            }, array_keys($source), $source)
+            : [];
+
+        return $data;
     }
 
     /**
-     * A required DropdownField must have a user selected attribute,
-     * so require an empty default for a required field
+     * Mark certain elements as disabled,
+     * regardless of the {@link setDisabled()} settings.
+     *
+     * These should be items that appear in the source list, not in addition to them.
      *
+     * @param array|SS_List $items Collection of values or items
+     * @return $this
+     */
+    public function setDisabledItems($items)
+    {
+        $this->disabledItems = $this->getListValues($items);
+        return $this;
+    }
+
+    /**
+     * Non-associative list of disabled item values
+     *
+     * @return array
+     */
+    public function getDisabledItems()
+    {
+        return $this->disabledItems;
+    }
+
+    /**
+     * Check if the given value is disabled
+     *
+     * @param string $value
      * @return bool
      */
-    public function getHasEmptyDefault()
+    protected function isDisabledValue($value)
     {
-        return parent::getHasEmptyDefault() || $this->Required();
+        if ($this->isDisabled()) {
+            return true;
+        }
+        return in_array($value, $this->getDisabledItems() ?? []);
+    }
+
+    public function getAttributes()
+    {
+        return array_merge(
+            parent::getAttributes(),
+            ['type' => null, 'value' => null]
+        );
     }
 
     /**
-     * @param array $properties
+     * Retrieve all values in the source array
+     *
+     * @return array
+     */
+    protected function getSourceValues()
+    {
+        return array_keys($this->getSource() ?? []);
+    }
+
+    /**
+     * Gets all valid values for this field.
+     *
+     * Does not include "empty" value if specified
+     *
+     * @return array
+     */
+    public function getValidValues()
+    {
+        $valid = array_diff($this->getSourceValues() ?? [], $this->getDisabledItems());
+        // Renumber indexes from 0
+        return array_values($valid ?? []);
+    }
+
+    /**
+     * Gets the source array not including any empty default values.
+     *
+     * @return array|ArrayAccess
+     */
+    public function getSource()
+    {
+        return $this->source;
+    }
+
+    /**
+     * Set the source for this list
+     *
+     * @param mixed $source
+     * @return $this
+     */
+    public function setSource($source)
+    {
+        $this->source = $this->getListMap($source);
+        return $this;
+    }
+
+    /**
+     * Given a list of values, extract the associative map of id => title
+     *
+     * @param mixed $source
+     * @return array Associative array of ids and titles
+     */
+    protected function getListMap($source)
+    {
+        // Extract source as an array
+        if ($source instanceof SS_List) {
+            $source = $source->map();
+        }
+        if ($source instanceof Map) {
+            $source = $source->toArray();
+        }
+        if (!is_array($source) && !($source instanceof ArrayAccess)) {
+            throw new \InvalidArgumentException('$source passed in as invalid type');
+        }
+
+        return $source;
+    }
+
+    /**
+     * Given a non-array collection, extract the non-associative list of ids
+     * If passing as array, treat the array values (not the keys) as the ids
+     *
+     * @param mixed $values
+     * @return array Non-associative list of values
+     */
+    protected function getListValues($values)
+    {
+        // Empty values
+        if (empty($values)) {
+            return [];
+        }
+
+        // Direct array
+        if (is_array($values)) {
+            return array_values($values ?? []);
+        }
+
+        // Extract lists
+        if ($values instanceof SS_List) {
+            return $values->column('ID');
+        }
+
+        return [trim($values ?? '')];
+    }
+
+    /**
+     * Determine if the current value of this field matches the given option value
+     *
+     * @param mixed $dataValue The value as extracted from the source of this field (or empty value if available)
+     * @param mixed $userValue The value as submitted by the user
+     * @return boolean True if the selected value matches the given option value
+     */
+    public function isSelectedValue($dataValue, $userValue)
+    {
+        if ($dataValue === $userValue) {
+            return true;
+        }
+
+        // Allow null to match empty strings
+        if ($dataValue === '' && $userValue === null) {
+            return true;
+        }
+
+        // Safety check against casting arrays as strings in PHP>5.4
+        if (is_array($dataValue) || is_array($userValue)) {
+            return false;
+        }
+
+        // For non-falsey values do loose comparison
+        if ($dataValue) {
+            return $dataValue == $userValue;
+        }
+
+        // For empty values, use string comparison to perform visible value match
+        return ((string) $dataValue) === ((string) $userValue);
+    }
+
+    public function performReadonlyTransformation()
+    {
+        /** @var LookupField $field */
+        $field = $this->castedCopy('SilverStripe\\Forms\\LookupField');
+        $field->setSource($this->getSource());
+        $field->setReadonly(true);
+
+        return $field;
+    }
+
+    public function performDisabledTransformation()
+    {
+        $clone = clone $this;
+        $clone->setDisabled(true);
+        return $clone;
+    }
+
+    /**
+     * Returns another instance of this field, but "cast" to a different class.
+     *
+     * @see FormField::castedCopy()
+     *
+     * @param string $classOrCopy
+     * @return FormField
+     */
+    public function castedCopy($classOrCopy)
+    {
+        $field = parent::castedCopy($classOrCopy);
+        if ($field instanceof SelectField) {
+            $field->setSource($this->getSource());
+        }
+        return $field;
+    }
+
+    /**
+     * Provides <option> list for the template
+     * This allows for a faster rendering of dropdowns with lots of options
+     *
      * @return string
      */
-    public function Field($properties = [])
+    public function renderOptionsHTML(): string
     {
-        $options = [];
+        // Some methods only exists for single selects
+        $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
+        $emptyString = $this->hasMethod('getEmptyString') ? $this->getEmptyString() : '';
 
-        // Add all options
-        foreach ($this->getSourceEmpty() as $value => $title) {
-            $options[] = $this->getFieldOption($value, $title);
+        $currentValue = $this->Value();
+        foreach ($source as $value => $title) {
+            $selected = '';
+            if ($this->isSelectedValue($value, $currentValue)) {
+                $selected = ' selected="selected"';
+            }
+            $disabled = '';
+            if ($this->isDisabledValue($value) && $title != $emptyString) {
+                $disabled = ' disabled="disabled"';
+            }
+            $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
+            $options[] = $item;
         }
 
-        $properties = array_merge($properties, [
-            'Options' => new ArrayList($options)
-        ]);
+        return implode("\n", $options);
+    }
 
+    /**
+     * @param array $properties
+     * @return string
+     */
+    public function Field($properties = [])
+    {
+        // Without this, changing the source will render the previous list due to cache
+        $OptionsHTML = new DBHTMLText('Options');
+        $OptionsHTML->setValue($this->renderOptionsHTML());
+        $properties['OptionsHTML'] = $OptionsHTML;
         return parent::Field($properties);
     }
 }

From 2c910a03ec85b43e4aed44a10885b759ea241ce5 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 14:28:23 +0200
Subject: [PATCH 5/9] don't use template cache

---
 src/Forms/SelectField.php | 26 ++++++++++++++++++--------
 1 file changed, 18 insertions(+), 8 deletions(-)

diff --git a/src/Forms/SelectField.php b/src/Forms/SelectField.php
index 5fa4fcef35d..10db5f65820 100644
--- a/src/Forms/SelectField.php
+++ b/src/Forms/SelectField.php
@@ -2,20 +2,17 @@
 
 namespace SilverStripe\Forms;
 
-use SilverStripe\ORM\SS_List;
-use SilverStripe\ORM\Map;
 use ArrayAccess;
+use SilverStripe\ORM\Map;
+use SilverStripe\ORM\SS_List;
 use SilverStripe\Core\Convert;
+use SilverStripe\ORM\FieldType\DBHTMLText;
 
 /**
  * Represents a field that allows users to select one or more items from a list
  */
 abstract class SelectField extends FormField
 {
-    private static $casting = [
-        'OptionsHTML' => 'HTMLFragment',
-    ];
-
     /**
      * Associative or numeric array of all dropdown items,
      * with array key as the submitted field value, and the array value as a
@@ -282,7 +279,7 @@ public function castedCopy($classOrCopy)
      *
      * @return string
      */
-    public function OptionsHTML(): string
+    public function renderOptionsHTML(): string
     {
         // Some methods only exists for single selects
         $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
@@ -301,7 +298,20 @@ public function OptionsHTML(): string
             $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
             $options[] = $item;
         }
-        
+
         return implode("\n", $options);
     }
+
+    /**
+     * @param array $properties
+     * @return string
+     */
+    public function Field($properties = [])
+    {
+        // Without this, changing the source will render the previous list due to cache
+        $OptionsHTML = new DBHTMLText('Options');
+        $OptionsHTML->setValue($this->renderOptionsHTML());
+        $properties['OptionsHTML'] = $OptionsHTML;
+        return parent::Field($properties);
+    }
 }

From 1d9aa26b560c4e5aaccd4ca45b259328d084257d Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 14:28:42 +0200
Subject: [PATCH 6/9] revert changes

---
 src/Forms/DropdownField.php | 393 ++++++++++--------------------------
 1 file changed, 111 insertions(+), 282 deletions(-)

diff --git a/src/Forms/DropdownField.php b/src/Forms/DropdownField.php
index 10db5f65820..765b8a9df31 100644
--- a/src/Forms/DropdownField.php
+++ b/src/Forms/DropdownField.php
@@ -2,316 +2,145 @@
 
 namespace SilverStripe\Forms;
 
-use ArrayAccess;
-use SilverStripe\ORM\Map;
-use SilverStripe\ORM\SS_List;
-use SilverStripe\Core\Convert;
-use SilverStripe\ORM\FieldType\DBHTMLText;
+use SilverStripe\ORM\ArrayList;
+use SilverStripe\View\ArrayData;
 
 /**
- * Represents a field that allows users to select one or more items from a list
+ * Dropdown field, created from a select tag.
+ *
+ * <b>Setting a $has_one relation</b>
+ *
+ * Using here an example of an art gallery, with Exhibition pages,
+ * each of which has a Gallery they belong to.  The Gallery class is also user-defined.
+ * <code>
+ *  static $has_one = array(
+ *      'Gallery' => 'Gallery',
+ *  );
+ *
+ *  public function getCMSFields() {
+ *      $fields = parent::getCMSFields();
+ *      $field = DropdownField::create('GalleryID', 'Gallery', Gallery::get()->map('ID', 'Title'))
+ *          ->setEmptyString('(Select one)');
+ *      $fields->addFieldToTab('Root.Content', $field, 'Content');
+ * </code>
+ *
+ * As you see, you need to put "GalleryID", rather than "Gallery" here.
+ *
+ * <b>Populate with Array</b>
+ *
+ * Example model definition:
+ * <code>
+ * class MyObject extends DataObject {
+ *   static $db = array(
+ *     'Country' => "Varchar(100)"
+ *   );
+ * }
+ * </code>
+ *
+ * Example instantiation:
+ * <code>
+ * DropdownField::create(
+ *   'Country',
+ *   'Country',
+ *   array(
+ *     'NZ' => 'New Zealand',
+ *     'US' => 'United States',
+ *     'GEM'=> 'Germany'
+ *   )
+ * );
+ * </code>
+ *
+ * <b>Populate with Enum-Values</b>
+ *
+ * You can automatically create a map of possible values from an {@link Enum} database column.
+ *
+ * Example model definition:
+ * <code>
+ * class MyObject extends DataObject {
+ *   static $db = array(
+ *     'Country' => "Enum('New Zealand,United States,Germany','New Zealand')"
+ *   );
+ * }
+ * </code>
+ *
+ * Field construction:
+ * <code>
+ * DropdownField::create(
+ *   'Country',
+ *   'Country',
+ *   singleton('MyObject')->dbObject('Country')->enumValues()
+ * );
+ * </code>
+ *
+ * <b>Disabling individual items</b>
+ *
+ * Individual items can be disabled by feeding their array keys to setDisabledItems.
+ *
+ * <code>
+ * $DrDownField->setDisabledItems( array( 'US', 'GEM' ) );
+ * </code>
+ *
+ * @see CheckboxSetField for multiple selections through checkboxes instead.
+ * @see ListboxField for a single <select> box (with single or multiple selections).
+ * @see TreeDropdownField for a rich and customizeable UI that can visualize a tree of selectable elements
  */
-abstract class SelectField extends FormField
+class DropdownField extends SingleSelectField
 {
-    /**
-     * Associative or numeric array of all dropdown items,
-     * with array key as the submitted field value, and the array value as a
-     * natural language description shown in the interface element.
-     *
-     * @var array|ArrayAccess
-     */
-    protected $source;
-
-    /**
-     * The values for items that should be disabled (greyed out) in the dropdown.
-     * This is a non-associative array
-     *
-     * @var array
-     */
-    protected $disabledItems = [];
-
-    /**
-     * @param string $name The field name
-     * @param string $title The field title
-     * @param array|ArrayAccess $source A map of the dropdown items
-     * @param mixed $value The current value
-     */
-    public function __construct($name, $title = null, $source = [], $value = null)
-    {
-        $this->setSource($source);
-        if (!isset($title)) {
-            $title = $name;
-        }
-        parent::__construct($name, $title, $value);
-    }
-
-    public function getSchemaStateDefaults()
-    {
-        $data = parent::getSchemaStateDefaults();
-        $disabled = $this->getDisabledItems();
-
-        // Add options to 'data'
-        $source = $this->getSource();
-        $data['source'] = (is_array($source))
-            ? array_map(function ($value, $title) use ($disabled) {
-                return [
-                    'value' => $value,
-                    'title' => $title,
-                    'disabled' => in_array($value, $disabled),
-                ];
-            }, array_keys($source), $source)
-            : [];
-
-        return $data;
-    }
-
-    /**
-     * Mark certain elements as disabled,
-     * regardless of the {@link setDisabled()} settings.
-     *
-     * These should be items that appear in the source list, not in addition to them.
-     *
-     * @param array|SS_List $items Collection of values or items
-     * @return $this
-     */
-    public function setDisabledItems($items)
-    {
-        $this->disabledItems = $this->getListValues($items);
-        return $this;
-    }
-
-    /**
-     * Non-associative list of disabled item values
-     *
-     * @return array
-     */
-    public function getDisabledItems()
-    {
-        return $this->disabledItems;
-    }
-
-    /**
-     * Check if the given value is disabled
-     *
-     * @param string $value
-     * @return bool
-     */
-    protected function isDisabledValue($value)
-    {
-        if ($this->isDisabled()) {
-            return true;
-        }
-        return in_array($value, $this->getDisabledItems() ?? []);
-    }
-
-    public function getAttributes()
-    {
-        return array_merge(
-            parent::getAttributes(),
-            ['type' => null, 'value' => null]
-        );
-    }
-
-    /**
-     * Retrieve all values in the source array
-     *
-     * @return array
-     */
-    protected function getSourceValues()
-    {
-        return array_keys($this->getSource() ?? []);
-    }
-
-    /**
-     * Gets all valid values for this field.
-     *
-     * Does not include "empty" value if specified
-     *
-     * @return array
-     */
-    public function getValidValues()
-    {
-        $valid = array_diff($this->getSourceValues() ?? [], $this->getDisabledItems());
-        // Renumber indexes from 0
-        return array_values($valid ?? []);
-    }
-
-    /**
-     * Gets the source array not including any empty default values.
-     *
-     * @return array|ArrayAccess
-     */
-    public function getSource()
-    {
-        return $this->source;
-    }
 
     /**
-     * Set the source for this list
+     * Build a field option for template rendering
      *
-     * @param mixed $source
-     * @return $this
+     * @param mixed $value Value of the option
+     * @param string $title Title of the option
+     * @return ArrayData Field option
      */
-    public function setSource($source)
+    protected function getFieldOption($value, $title)
     {
-        $this->source = $this->getListMap($source);
-        return $this;
-    }
+        // Check selection
+        $selected = $this->isSelectedValue($value, $this->Value());
 
-    /**
-     * Given a list of values, extract the associative map of id => title
-     *
-     * @param mixed $source
-     * @return array Associative array of ids and titles
-     */
-    protected function getListMap($source)
-    {
-        // Extract source as an array
-        if ($source instanceof SS_List) {
-            $source = $source->map();
-        }
-        if ($source instanceof Map) {
-            $source = $source->toArray();
-        }
-        if (!is_array($source) && !($source instanceof ArrayAccess)) {
-            throw new \InvalidArgumentException('$source passed in as invalid type');
+        // Check disabled
+        $disabled = false;
+        if ($this->isDisabledValue($value) && $title != $this->getEmptyString()) {
+            $disabled = 'disabled';
         }
 
-        return $source;
+        return new ArrayData([
+            'Title' => (string)$title,
+            'Value' => $value,
+            'Selected' => $selected,
+            'Disabled' => $disabled,
+        ]);
     }
 
     /**
-     * Given a non-array collection, extract the non-associative list of ids
-     * If passing as array, treat the array values (not the keys) as the ids
+     * A required DropdownField must have a user selected attribute,
+     * so require an empty default for a required field
      *
-     * @param mixed $values
-     * @return array Non-associative list of values
-     */
-    protected function getListValues($values)
-    {
-        // Empty values
-        if (empty($values)) {
-            return [];
-        }
-
-        // Direct array
-        if (is_array($values)) {
-            return array_values($values ?? []);
-        }
-
-        // Extract lists
-        if ($values instanceof SS_List) {
-            return $values->column('ID');
-        }
-
-        return [trim($values ?? '')];
-    }
-
-    /**
-     * Determine if the current value of this field matches the given option value
-     *
-     * @param mixed $dataValue The value as extracted from the source of this field (or empty value if available)
-     * @param mixed $userValue The value as submitted by the user
-     * @return boolean True if the selected value matches the given option value
-     */
-    public function isSelectedValue($dataValue, $userValue)
-    {
-        if ($dataValue === $userValue) {
-            return true;
-        }
-
-        // Allow null to match empty strings
-        if ($dataValue === '' && $userValue === null) {
-            return true;
-        }
-
-        // Safety check against casting arrays as strings in PHP>5.4
-        if (is_array($dataValue) || is_array($userValue)) {
-            return false;
-        }
-
-        // For non-falsey values do loose comparison
-        if ($dataValue) {
-            return $dataValue == $userValue;
-        }
-
-        // For empty values, use string comparison to perform visible value match
-        return ((string) $dataValue) === ((string) $userValue);
-    }
-
-    public function performReadonlyTransformation()
-    {
-        /** @var LookupField $field */
-        $field = $this->castedCopy('SilverStripe\\Forms\\LookupField');
-        $field->setSource($this->getSource());
-        $field->setReadonly(true);
-
-        return $field;
-    }
-
-    public function performDisabledTransformation()
-    {
-        $clone = clone $this;
-        $clone->setDisabled(true);
-        return $clone;
-    }
-
-    /**
-     * Returns another instance of this field, but "cast" to a different class.
-     *
-     * @see FormField::castedCopy()
-     *
-     * @param string $classOrCopy
-     * @return FormField
+     * @return bool
      */
-    public function castedCopy($classOrCopy)
+    public function getHasEmptyDefault()
     {
-        $field = parent::castedCopy($classOrCopy);
-        if ($field instanceof SelectField) {
-            $field->setSource($this->getSource());
-        }
-        return $field;
+        return parent::getHasEmptyDefault() || $this->Required();
     }
 
     /**
-     * Provides <option> list for the template
-     * This allows for a faster rendering of dropdowns with lots of options
-     *
+     * @param array $properties
      * @return string
      */
-    public function renderOptionsHTML(): string
+    public function Field($properties = [])
     {
-        // Some methods only exists for single selects
-        $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
-        $emptyString = $this->hasMethod('getEmptyString') ? $this->getEmptyString() : '';
+        $options = [];
 
-        $currentValue = $this->Value();
-        foreach ($source as $value => $title) {
-            $selected = '';
-            if ($this->isSelectedValue($value, $currentValue)) {
-                $selected = ' selected="selected"';
-            }
-            $disabled = '';
-            if ($this->isDisabledValue($value) && $title != $emptyString) {
-                $disabled = ' disabled="disabled"';
-            }
-            $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
-            $options[] = $item;
+        // Add all options
+        foreach ($this->getSourceEmpty() as $value => $title) {
+            $options[] = $this->getFieldOption($value, $title);
         }
 
-        return implode("\n", $options);
-    }
+        $properties = array_merge($properties, [
+            'Options' => new ArrayList($options)
+        ]);
 
-    /**
-     * @param array $properties
-     * @return string
-     */
-    public function Field($properties = [])
-    {
-        // Without this, changing the source will render the previous list due to cache
-        $OptionsHTML = new DBHTMLText('Options');
-        $OptionsHTML->setValue($this->renderOptionsHTML());
-        $properties['OptionsHTML'] = $OptionsHTML;
         return parent::Field($properties);
     }
 }

From 328f94553edeadfd006e836775111c40fdf4267c Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 14:46:32 +0200
Subject: [PATCH 7/9] move methods to dropdown field

---
 src/Forms/DropdownField.php | 40 +++++++++++++++++++++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/src/Forms/DropdownField.php b/src/Forms/DropdownField.php
index 765b8a9df31..90574d3b690 100644
--- a/src/Forms/DropdownField.php
+++ b/src/Forms/DropdownField.php
@@ -2,8 +2,10 @@
 
 namespace SilverStripe\Forms;
 
+use SilverStripe\Core\Convert;
 use SilverStripe\ORM\ArrayList;
 use SilverStripe\View\ArrayData;
+use SilverStripe\ORM\FieldType\DBHTMLText;
 
 /**
  * Dropdown field, created from a select tag.
@@ -124,6 +126,39 @@ public function getHasEmptyDefault()
         return parent::getHasEmptyDefault() || $this->Required();
     }
 
+    /**
+     * Provides <option> list for the template
+     * This allows for a faster rendering of dropdowns with lots of options
+     *
+     * @return string
+     */
+    public function renderOptionsHTML(): string
+    {
+        // Some methods only exists for single selects
+        $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
+        $emptyString = $this->hasMethod('getEmptyString') ? $this->getEmptyString() : '';
+
+        $currentValue = $this->Value();
+        foreach ($source as $value => $title) {
+            // It's an opt group, ignore since it has its own template
+            if (is_array($title)) {
+                continue;
+            }
+            $selected = '';
+            if ($this->isSelectedValue($value, $currentValue)) {
+                $selected = ' selected="selected"';
+            }
+            $disabled = '';
+            if ($this->isDisabledValue($value) && $title != $emptyString) {
+                $disabled = ' disabled="disabled"';
+            }
+            $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
+            $options[] = $item;
+        }
+
+        return implode("\n", $options);
+    }
+
     /**
      * @param array $properties
      * @return string
@@ -141,6 +176,11 @@ public function Field($properties = [])
             'Options' => new ArrayList($options)
         ]);
 
+        // Without this, changing the source will render the previous list due to cache
+        $OptionsHTML = new DBHTMLText('Options');
+        $OptionsHTML->setValue($this->renderOptionsHTML());
+        $properties['OptionsHTML'] = $OptionsHTML;
+
         return parent::Field($properties);
     }
 }

From b4d85320885d19b619050aba7fdaa95d6ae5f823 Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 14:47:19 +0200
Subject: [PATCH 8/9] prevent child classes side effects

---
 src/Forms/SelectField.php | 49 +++------------------------------------
 1 file changed, 3 insertions(+), 46 deletions(-)

diff --git a/src/Forms/SelectField.php b/src/Forms/SelectField.php
index 10db5f65820..edc3f4f0401 100644
--- a/src/Forms/SelectField.php
+++ b/src/Forms/SelectField.php
@@ -2,17 +2,16 @@
 
 namespace SilverStripe\Forms;
 
-use ArrayAccess;
-use SilverStripe\ORM\Map;
 use SilverStripe\ORM\SS_List;
-use SilverStripe\Core\Convert;
-use SilverStripe\ORM\FieldType\DBHTMLText;
+use SilverStripe\ORM\Map;
+use ArrayAccess;
 
 /**
  * Represents a field that allows users to select one or more items from a list
  */
 abstract class SelectField extends FormField
 {
+
     /**
      * Associative or numeric array of all dropdown items,
      * with array key as the submitted field value, and the array value as a
@@ -272,46 +271,4 @@ public function castedCopy($classOrCopy)
         }
         return $field;
     }
-
-    /**
-     * Provides <option> list for the template
-     * This allows for a faster rendering of dropdowns with lots of options
-     *
-     * @return string
-     */
-    public function renderOptionsHTML(): string
-    {
-        // Some methods only exists for single selects
-        $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();
-        $emptyString = $this->hasMethod('getEmptyString') ? $this->getEmptyString() : '';
-
-        $currentValue = $this->Value();
-        foreach ($source as $value => $title) {
-            $selected = '';
-            if ($this->isSelectedValue($value, $currentValue)) {
-                $selected = ' selected="selected"';
-            }
-            $disabled = '';
-            if ($this->isDisabledValue($value) && $title != $emptyString) {
-                $disabled = ' disabled="disabled"';
-            }
-            $item = '<option value="' . Convert::raw2xml($value) . '"' . $selected . $disabled . '>' . Convert::raw2xml($title) . '</option>';
-            $options[] = $item;
-        }
-
-        return implode("\n", $options);
-    }
-
-    /**
-     * @param array $properties
-     * @return string
-     */
-    public function Field($properties = [])
-    {
-        // Without this, changing the source will render the previous list due to cache
-        $OptionsHTML = new DBHTMLText('Options');
-        $OptionsHTML->setValue($this->renderOptionsHTML());
-        $properties['OptionsHTML'] = $OptionsHTML;
-        return parent::Field($properties);
-    }
 }

From caa42c304f405cb27bb62e473d45351b838a36dd Mon Sep 17 00:00:00 2001
From: Thomas Portelange <thomas@lekoala.be>
Date: Mon, 26 Jun 2023 16:55:30 +0200
Subject: [PATCH 9/9] Update src/Forms/DropdownField.php

Co-authored-by: Michal Kleiner <mk@011.nz>
---
 src/Forms/DropdownField.php | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/Forms/DropdownField.php b/src/Forms/DropdownField.php
index 90574d3b690..2793bb34fe2 100644
--- a/src/Forms/DropdownField.php
+++ b/src/Forms/DropdownField.php
@@ -132,7 +132,7 @@ public function getHasEmptyDefault()
      *
      * @return string
      */
-    public function renderOptionsHTML(): string
+    private function renderOptionsHTML(): string
     {
         // Some methods only exists for single selects
         $source = $this->hasMethod('getSourceEmpty') ? $this->getSourceEmpty() : $this->getSource();