Disable "delete" in TYPO3 context menu for pages under custom condition

ContextMenuActions.js

/*
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

/**
 * Module: TYPO3/CMS/ExtensionKey/ContextMenuActions
 *
 * This file goes to EXT:extension_key/Resources/Public/JavaScript/ContextMenuActions.js.
 *
 * JavaScript to notify that delete action is disabled from context menu
 * @exports TYPO3/CMS/ExtensionKey/ContextMenuActions
 */
define(function () {
    'use strict';

    /**
     * @exports TYPO3/CMS/ExtensionKey/ContextMenuActions
     */
    var ContextMenuActions = {};

    /**
     * Notify that a page cannot be deleted
     *
     * @param {string} table
     * @param {int} uid of the page
     */
    ContextMenuActions.notifyCannotDelete = function (table, uid) {
        if (table === 'pages') {
            // TODO: Use localization, e.g., using 'data' attributes from $(this)
            top.TYPO3.Notification.error('My title goes here', 'My message goes here', 5);
        }
    };

    return ContextMenuActions;
});

ext_localconf.php

<?php
defined('TYPO3_MODE') or die();

if (TYPO3_MODE === 'BE') {
    // You should use current timestamp (not this very value) or leave it empty
    $GLOBALS['TYPO3_CONF_VARS']['BE']['ContextMenu']['ItemProviders'][1488274371] =
        \Vendor\ExtensionKey\Backend\ContextMenu\PageViewRecordsElementItemProvider::class;
}

PageViewRecordsElementItemProvider.php

<?php
/**
 * This file is part of the TYPO3 CMS project.
 *
 * It is free software; you can redistribute it and/or modify it under
 * the terms of the GNU General Public License, either version 2
 * of the License, or any later version.
 *
 * For the full copyright and license information, please read the
 * LICENSE.txt file that was distributed with this source code.
 *
 * The TYPO3 project - inspiring people to share!
 */

namespace Vendor\ExtensionKey\Backend\ContextMenu;

use TYPO3\CMS\Backend\ContextMenu\ItemProviders\AbstractProvider;
use TYPO3\CMS\Core\Imaging\Icon;
use TYPO3\CMS\Core\Utility\GeneralUtility;

/**
 * This file goes to EXT:extension_key/Classes/Backend/ContextMenu/PageViewRecordsElementItemProvider.php.
 */
class PageViewRecordsElementItemProvider extends AbstractProvider
{
    /**
     * Checks if this provider may be called to post-process the list of context menu items (for pages).
     *
     * @return bool
     */
    public function canHandle(): bool
    {
        return $this->table === 'pages';
    }

    /**
     * Returns the provider priority which is used for determining the order in which providers are processing items
     * to the result array. Highest priority means provider is evaluated first.
     *
     * We want to be after @see \TYPO3\CMS\Backend\ContextMenu\ItemProviders\PageProvider::getPriority() anyway.
     *
     * BEWARE: Returned priority should logically not clash with another provider.
     *         Please check @see \TYPO3\CMS\Backend\ContextMenu\ContextMenu::getAvailableProviders() if needed.
     *
     * @return int
     */
    public function getPriority(): int
    {
        return 90;
    }

    /**
     * Registers the additional callback-module which will allow us to display a notification
     * whenever the user tries to delete a protected page.
     *
     * @param string $itemName
     * @return array
     */
    protected function getAdditionalAttributes(string $itemName): array
    {
        return [
            // BEWARE!!! THIS MUST ALWAYS START WITH "TYPO3/CMS/" (and no "Vendor" segment here)
            'data-callback-module' => 'TYPO3/CMS/ExtensionKey/ContextMenuActions',
            // TODO: Add any other useful "data-" attribute you'd like to use in your JavaScript (e.g., localized messages)
        ];
    }

    /**
     * We do not "add" items to the context menu but will disable the deletion of pages
     * if some condition is met.
     *
     * @param array $items
     * @return array
     */
    public function addItems(array $items): array
    {
        // TODO: implement some custom condition
        // Current table is: $this->table
        // Current UID is: $this->identifier
        $disableDelete = true;
        $itemName = 'delete';

        if ($disableDelete && isset($items[$itemName])) {
            // Mark the "delete" item as disabled and show a notification message when clicked
            /** @var \TYPO3\CMS\Core\Imaging\IconFactory $iconFactory */
            $iconFactory = GeneralUtility::makeInstance(\TYPO3\CMS\Core\Imaging\IconFactory::class);
            $items[$itemName]['icon'] = $iconFactory->getIcon('actions-delete', Icon::SIZE_SMALL, 'overlay-hidden')->render();

            // We replace the action when we click the context menu item by our custom notification
            $items[$itemName]['callbackAction'] = 'notifyCannotDelete';
            $items[$itemName]['additionalAttributes'] = $this->getAdditionalAttributes($itemName);
        }

        return $items;
    }
}

Purpose of this gist is to disable the "Delete" menu entry when showing the context menu of a "pages" record:

@xperseguers you should check if the item is present before modifying it. If user has no delete permission for a page, the delete item will not be there.

@tmotyl Good idea!