There are six areas that specific focus should be given as plugin-related changes coming in 5.5:
1.) Note the version of jQuery shipped in core will be updated in 5.6 and as a first step jquery-migrate is no longer enqueued by default in 5.5. Updates to your code are required if you rely on jquery-migrate or .live() to function properly as they are being removed. You can verify this by checking your code with WP_DEBUG enabled to make sure you are not using deprecated code. Please do this to avoid unnecessary support requests and negative reviews for your plugin:
https://make.wordpress.org/core/2020/06/29/updating-jquery-version-shipped-with-wordpress/
2.) Note the new plugin auto-update UI and how to ensure your plugin is ready for the new auto-updates system:
https://make.wordpress.org/core/2020/07/15/controlling-plugin-and-theme-auto-updates-ui-in-wordpress-5-5/
3.) Note the Block Directory guidelines (https://make.wordpress.org/plugins/2020/07/22/proposed-block-directory-guidelines/) and how to get your block plugin added to the Block Directory:
https://make.wordpress.org/plugins/2020/07/11/you-can-now-add-your-own-plugins-to-the-block-directory/
4.) Note the new XML sitemap feature and how it can be integrated with your plugin:
https://make.wordpress.org/core/2020/07/22/new-xml-sitemaps-functionality-in-wordpress-5-5/
5.) Note the deprecated $HTTP_RAW_POST_DATA global variable in the PHP related improvements & changes devnote:
https://make.wordpress.org/core/2020/07/14/php-related-improvements-changes-wordpress-5-5-edition/
6.) Note the various plugin recommendations in the miscellaneous changes devnote:
https://make.wordpress.org/core/2020/07/29/miscellaneous-developer-focused-changes-in-wordpress-5-5/
In order to ensure compatibility, you can download and beta test your plugin with the latest WordPress version here: https://make.wordpress.org/core/handbook/testing/beta-testing/
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