In Drupal Views, "grouping" refers to the feature found in the Format section's Style options. When configuring a view's format (Table, HTML List, Grid, etc.), you can select one or more fields to group results by. This creates visual sections with headers for each unique field value, organizing content into logical categories.
Occasionally I find myself needing plugin-like functionality, where users/downstream can throw a class into a folder and expect it to work. My script is supposed to find and instantiate these plugins during runtime without keeping track of their existence.
In a regular Drupal module, one would usually use the plugin architecture, but that comes with its overhead of boilerplate code and may not be the solution for the simplest of use cases.
When migrating content with the Drupal 8 migrate module, the creation and updating of new entities may fire lots of custom module hooks. This may or may not be desired; if you have found yourself here, it probably interferes with the source data in a problematic way, or unnecessarily slows down the migration process.
The cleanest way I found to stop specific hooks for specific migrations, is to add a dummy/meta field to the migration and check for its value in the hook.
This is a technical description of the 3.x branch of the module. For the newer 4.x branch, see this article.
This is a technical description of the 3.x branch of the module. For the newer 4.x branch, see this article.