Redundant caches when using ArgumentsViewHelper

[vertexvaar]

Bug Report

Current Behavior Using the \GeorgRinger\News\ViewHelpers\MultiCategoryLink\ArgumentsViewHelper will create duplicate cache entries for the same selection of categories, because the ViewHelper does keep track of the order in which categories are selected.

• Select Category 5 $categoryList = '5'
• Select Category 14 $categoryList = '5,14'
• Deselect Category 5 $categoryList = '14'
• Select Category 5 $categoryList = '14,5'
• Deselect all $categoryList = ''
• Select Category 5 $categoryList = ',5'

Expected behavior/output Adding and removing a category must create uniform overwriteDemand.categories parameters, so the cache hash calculation returns the same hash for each unique selection.

• Select Category 5 $categoryList = '5'
• Select Category 14 $categoryList = '5,14'
• Deselect Category 5 $categoryList = '14'
• Select Category 5 $categoryList = '5,14' <-- Order the categories to prevent duplicate cache entry with different
• Deselect all $categoryList = ''
• Select Category 5 $categoryList = '5' <-- Without leading comma

Environment

• TYPO3 version(s): 9LTS, 10LTS, 11LTS, 12LTS
• news version: ^7.2, dev-main
• Composer Mode: yes
• OS: docker: php:7.2-fpm and up

Possible Solution Use this code to add or remove categories from the list of categories and prevent leading commas.

        // All IDs are numeric. Hence, split and type cast.
        $categoryList = GeneralUtility::intExplode(',', $arguments['list'], true);
        if ($arguments['mode'] === 'add') {
            $categoryList[] = $categoryId;
        } else {
            // array_diff has the advantage, that it does not care how often the searched value occurs.
            $categoryList = array_diff($categoryList, [$categoryId]);
        }
        // Ensure each ID to only occur once
        $categoryList = array_unique($categoryList);
        // Sort IDs, so lists are more uniform and less duplicate caches are generated
        sort($categoryList);
        $categoryList = implode(',', $categoryList);

[georgringer]

wanna do a PR then?