Date: 2020-10-26

Status

accepted

Context

WikibaseRepo and WikibaseClient classes act as top level factories for services required inside of the respective extension.

The methods to create/retrieve them do not follow a standardized interface, and as many of them are required to build other services, the classes also hold a substantial amount of code to keep and pass references to the created instances once created. This code is low in conceptual value but highly repetitive and a burden on developers.

Services which are required in WikibaseRepo and WikibaseClient alike, e.g. FormatterCacheFactory, may also exhibit redundant implementations of their instantiator function as there is no ability to reuse them.

MediaWiki supports a concept called ServiceWiring which allows for the registration of services, is an important building block of recent MediaWiki and implements the well-known PSR 11 container interface.

Decision

We will use MediaWiki ServiceWiring to describe and connect the services on which the wikibase repo and client extensions rely.

Consequences

The services described in the wikibase repo and wikibase client extensions will be migrated to respective service wiring files (e.g. repo/WikibaseRepo.ServiceWiring.php).

Boilerplate code, holding references to instances of services inside WikibaseRepo and WikibaseClient, can be removed.

The WikibaseRepo and WikibaseClient client classes will remain as type-safe accessors to the services governed by the service container (as done in MediaWiki core).

The ability to "make joint registration [of services] possible", as mentioned in ADR #13, is not immediately implemented, but the standardized interface eases future decisions in that direction.