first commit

plugins/fields/user/params/user.xml

@@ -0,0 +1,18 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<form>
+	<field
+		name="default_value"
+		type="user"
+		label="PLG_FIELDS_USER_DEFAULT_VALUE_LABEL"
+		validate="UserId"
+	/>
+	<fields name="params" label="COM_FIELDS_FIELD_BASIC_LABEL">
+		<fieldset name="basic">
+			<field
+				name="show_on"
+				type="hidden"
+				filter="unset"
+			/>
+		</fieldset>
+	</fields>
+</form>

plugins/fields/user/services/provider.php

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+<?php
+
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  Fields.user
+ *
+ * @copyright   (C) 2023 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+\defined('_JEXEC') or die;
+
+use Joomla\CMS\Extension\PluginInterface;
+use Joomla\CMS\Factory;
+use Joomla\CMS\Plugin\PluginHelper;
+use Joomla\CMS\User\UserFactoryInterface;
+use Joomla\DI\Container;
+use Joomla\DI\ServiceProviderInterface;
+use Joomla\Event\DispatcherInterface;
+use Joomla\Plugin\Fields\User\Extension\User;
+
+return new class () implements ServiceProviderInterface {
+    /**
+     * Registers the service provider with a DI container.
+     *
+     * @param   Container  $container  The DI container.
+     *
+     * @return  void
+     *
+     * @since   4.3.0
+     */
+    public function register(Container $container)
+    {
+        $container->set(
+            PluginInterface::class,
+            function (Container $container) {
+                $plugin     = new User(
+                    $container->get(DispatcherInterface::class),
+                    (array) PluginHelper::getPlugin('fields', 'user')
+                );
+                $plugin->setApplication(Factory::getApplication());
+                $plugin->setUserFactory($container->get(UserFactoryInterface::class));
+
+                return $plugin;
+            }
+        );
+    }
+};

plugins/fields/user/src/Extension/User.php

@@ -0,0 +1,51 @@
+<?php
+
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  Fields.user
+ *
+ * @copyright   (C) 2017 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+namespace Joomla\Plugin\Fields\User\Extension;
+
+use Joomla\CMS\Form\Form;
+use Joomla\CMS\User\UserFactoryAwareTrait;
+use Joomla\Component\Fields\Administrator\Plugin\FieldsPlugin;
+use Joomla\Event\SubscriberInterface;
+
+// phpcs:disable PSR1.Files.SideEffects
+\defined('_JEXEC') or die;
+// phpcs:enable PSR1.Files.SideEffects
+
+/**
+ * Fields User Plugin
+ *
+ * @since  3.7.0
+ */
+final class User extends FieldsPlugin implements SubscriberInterface
+{
+    use UserFactoryAwareTrait;
+
+    /**
+     * Transforms the field into a DOM XML element and appends it as a child on the given parent.
+     *
+     * @param   stdClass    $field   The field.
+     * @param   \DOMElement  $parent  The field node parent.
+     * @param   Form        $form    The form.
+     *
+     * @return  \DOMElement
+     *
+     * @since   3.7.0
+     */
+    public function onCustomFieldsPrepareDom($field, \DOMElement $parent, Form $form)
+    {
+        if ($this->getApplication()->isClient('site')) {
+            // The user field is not working on the front end
+            return;
+        }
+
+        return parent::onCustomFieldsPrepareDom($field, $parent, $form);
+    }
+}

plugins/fields/user/tmpl/user.php

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+<?php
+
+/**
+ * @package     Joomla.Plugin
+ * @subpackage  Fields.User
+ *
+ * @copyright   (C) 2017 Open Source Matters, Inc. <https://www.joomla.org>
+ * @license     GNU General Public License version 2 or later; see LICENSE.txt
+ */
+
+defined('_JEXEC') or die;
+
+$value = $field->value;
+
+if ($value == '') {
+    return;
+}
+
+$value = (array) $value;
+$texts = [];
+
+foreach ($value as $userId) {
+    if (!$userId) {
+        continue;
+    }
+
+    $user = $this->getUserFactory()->loadUserById($userId);
+
+    if ($user) {
+        // Use the Username
+        $texts[] = $user->name;
+        continue;
+    }
+
+    // Fallback and add the User ID if we get no JUser Object
+    $texts[] = $userId;
+}
+
+echo htmlentities(implode(', ', $texts));

plugins/fields/user/user.xml

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+<?xml version="1.0" encoding="UTF-8"?>
+<extension type="plugin" group="fields" method="upgrade">
+	<name>plg_fields_user</name>
+	<author>Joomla! Project</author>
+	<creationDate>2016-03</creationDate>
+	<copyright>(C) 2016 Open Source Matters, Inc.</copyright>
+	<license>GNU General Public License version 2 or later; see LICENSE.txt</license>
+	<authorEmail>admin@joomla.org</authorEmail>
+	<authorUrl>www.joomla.org</authorUrl>
+	<version>3.7.0</version>
+	<description>PLG_FIELDS_USER_XML_DESCRIPTION</description>
+	<namespace path="src">Joomla\Plugin\Fields\User</namespace>
+	<files>
+		<folder>params</folder>
+		<folder plugin="user">services</folder>
+		<folder>src</folder>
+		<folder>tmpl</folder>
+	</files>
+	<languages>
+		<language tag="en-GB">language/en-GB/plg_fields_user.ini</language>
+		<language tag="en-GB">language/en-GB/plg_fields_user.sys.ini</language>
+	</languages>
+</extension>