magento2 Module structure Catalog Module structure

Example

For now I think the catalog module contains almost everything you can add to a module.

• Api - Contains the service contracts. A set of interfaces that should not be changed unless the minor version changes. Not mandatory for a custom module but nice to have for comercial extensions.
  • Data - Data interfaces. Each interface must have a model that implements it (example: interface for product model)
  • ProductRepositoryInterface.php - interfaces for repositories (must also have an implementation)
  • ... - others as above
• Block - blocks used in the layout for frontend and backend
  • Adminhtml - blocks used for backend
  • Category - frontend related blocks. Can be nested in as many folders as you like, but not mandatory
  • ... - same as above
• Console - folder containing cli commands
• Controller - contains frontend and backend controllers
  • Adminhtml - backend controllers
  • Category - frontend related controllers. Can be nested in as many folders as you like, but not mandatory
  • ... - same as above.
• Cron - code that should be executed via cron
• etc - contains module configuration xml files
  • frontend - contains configuration files loaded only on frontend
  • adminhtml - contains configuration files loaded only on backend
  • webapi_rest - contains configuration files loaded only for the rest api
  • webapi_soapt - contains configuration files loaded only for the SOAP api
  • acl.xml - ACL definitions
  • catalog_attributes.xml - default attributes for catalog entities.
  • catalog_attributes.xsd - validation schema for file above.
  • config.xml - default values for config settings
  • crontab.xml - cron jobs scheduling
  • di.xml - dependency injection preferences. (can also reside in adminhtml, frontend, webapi_*)
  • events.xml - observers declaration for events (can also reside in adminhtml, frontend)
  • indexer.xml - settings for different indexes that need to be executed when data changes
  • module.xml - the module declaration file
  • product_* - product related settings.
  • webapi.xml - webapi declaration paths.
  • widget.xml - widgets declarations.
• Helper - different module helpers
• i18n - language translation files
• Model - models, simple as that. they can be nested in as many folders as you like, but it's not mandatory.
• Observer - event observer classes
• Plugin - around|before|after plugins for different public methods.
• Pricing - pricing related classes. This is module specific. You can have as many folders as you like like this if you don't want to place them in the models folder.
• Setup - install/upgrade related files (installing upgrading schema and data)
• Test - unit tests
• Ui - ui components related classes.
• view - the html related part. The V in MVC.
  • adminhtml - admin related files
    • layout - xml layouts for adminhtml
    • templates - phtml templates for adminhtml
    • ui_compoenent - ui components related files (declaration)
    • web - assets (js, images)
    • requirejs-config.js - configuration for require.js
  • base - files used for both frontend and backend.
    • can have same subfolder structure as adminhtml
  • frontend - frontend related files
    • can have same subfolder structure as adminhtml
• composer.json - not mandatory, but nice to have if you distribute your module
• registration.php - the module registration file.
• Licence*.txt, readme.md - you know what this means. They are not mandatory