Core Platform Team/Initiative/globals/Initiative Vision

< globals

Vision: MediaWiki does not use global variables to manage state.
Stakeholder(s): MediaWiki developers (core and extensions) will benefit from clearer, more testable code Extension developers (in WMF and elsewhere) will have more control over the behavior of pages their extension manages. Quality + test engineering may be interested since we are making code more testable by removing access to global state The Performance team should be consulted to ensure the proposed changes do not introduce performance issues	Problem: For historical reasons, MediaWiki uses a number of global variables to represent the execution context. Usually, these variables are not accessed directly but via a RequestContext, but they still exist, and are in fact needed by RequestContext. RequestContext is a kitchen-sink, bundling access to too many parts of the system, causing spurious dependencies to be introduced across the code base.		Solution: Define a clear pattern for creating a RequestContext, and providing it to the code that needs it. Deprecate some parts of RequestContext to make it more lightweight Similarly, provide a clear information flow to provide relevant information to code that should not have access to a full RequestContext. Replace global variables with stubs that emit deprecation warnings.	Aligned Goals: Improve code quality by reducing coupling Improve code health by improving testability Improve maintainability by modeling domain concepts clearly	Success Metrics: