This is a technical description of the 3.x branch of the module. For the newer 4.x branch, see this article.
Simple XML sitemap 3.1 has been released
The third major version of simple_sitemap has been long in the making bringing a more reliable generation process, a significantly more versatile API and many new functionalities. The first minor ugrade of the 3.x branch comes with views support and human readable sitemaps.
Major new features in 3.1
Views and views arguments support
Including view display URLs in the sitemap has been possible through adding these URLs as custom links in the UI (or via the API).
View variations created by view arguments however are tedious to include as one would have to include every version of the URL.
Thanks to @WalkingDexter for his tremendous work on this submodule!
Human-readable sitemaps with XSL stylesheets
This will not change how bots interact with the sitemaps, it will however make the sitemaps readable and sortable for humans. This can be helpful when debugging the sitemap content or using the sitemap to visually present content to users.
You can see the list of bug fixess and improvements on the module's release page.
The module upgrades fine from any of the 2.x and 3.x versions.
To upgrade the module via composer,
$ composer require 'drupal/simple_sitemap:^3.1' can be used. Afterwards, just visit /update.php, or run
$ drush updb to update the module's storage.
For more information about the 3.x branch of the module, see this post. I invite you to watch this space for a more in-depth technical tutorial on how to programmatically create sitemap types. Also feel free to leave a comment below!