Skill: Autoloading and DI

Read the bundled conventions before applying this skill. It is independently usable; no umbrella skill or particular tool is required.

Decisions that affect behavior

• Composer is the only class autoloader. Entry scripts must load its autoloader before referencing Yii or yii\.... Yii::autoload(), Yii::$classMap, and framework/classes.php are removed. Put application namespaces in the existing Composer autoload/autoload-dev structure and regenerate the autoloader only when its mapping changes; an alias such as @app is not an autoload mapping.
• Prefer an application subclass configured as the relevant component for ordinary customization. A deliberate same-FQCN replacement through Composer classmap and exclusions must implement the original API and cannot extend itself. Do not introduce such replacement for a routine component override.
• Distinguish class construction from service lookup. Yii::$container definitions configure object creation; application/module components register named, lazily created services that their service locator reuses. params contains values, not container bindings. A component ID need not equal its class name.
• Ordinary container class definitions create new objects on repeated resolution; setSingleton() and object-instance definitions share an instance. Select the lifetime required by the application, especially for mutable services in workers. Do not make a service a singleton simply to fix dependency resolution.
• Register interfaces and non-inferable constructor arguments explicitly. Do not assume arbitrary union/intersection types have an unambiguous injectable value; inspect the resolved Container implementation and supply the intended argument.
• Keep bootstrap order and configuration merging intact. A service definition does not by itself mean the service has bootstrapped. Resolve module-scoped components from the intended module rather than silently using the application.

Observable acceptance

Exercise the relevant entrypoint with the application’s generated autoloader and resolve the affected class/service through the same path as production. Verify its concrete type, required constructor values, and repeated-resolution identity for the intended lifetime. For a changed namespace, include a class outside the already loaded path so an accidental prior include cannot hide a broken mapping. Preserve both web and console startup when their shared configuration changed.

Do not install dependencies or rewrite an unrelated autoload map merely to run a check. Report absent vendor files or runtime requirements as verification gaps.

Evidence routes

Inspect framework/Yii.php, framework/BaseYii.php::createObject(), framework/composer.json, framework/di/Container.php, framework/di/ServiceLocator.php, and framework/base/Application.php. Regression examples are tests/framework/di/ContainerTest.php and tests/framework/di/ServiceLocatorTest.php. Relevant guides are concept-autoloading, concept-di-container, concept-service-locator, concept-configurations, and structure-applications.

Install and activate this skill

Select yii2-autoload-di in the installation and client verification guide. Install the complete bundle, including referenced resources. The canonical SKILL.md is also available for direct reading.

Continue with the related framework guide.