Help:Extension:Translate/Developer guide

Translate extension is a large extension with hundreds of classes. This page provides guidance for developers who want to work on the code. After reading this page and linked documents you will better understand how code in Translate is organized and what special conventions are used. General MediaWiki development policies, coding conventions and how to use tools like Gerrit and Phabricator are out of scope. You are assumed to be familiar with these topics and when they apply to Translate, it will not be repeated here.

Translate extension is undergoing many large migrations simultaneously. Here we list the major migrations that are on-going, and detail which style is preferred for new code. Generally, when modifying existing code, it is better to keep to current style, and do migrations separately. Some smaller cleanups are okay to do when touching code.

Namespace migration
We are in process of migrating all Translate code under the namespace. All namespaced code is placed under the  directory. All new PHP files should be put in an appropriate namespace. See Extension:Translate/Namespaces for guidance which namespaces are going to be available. Namespaces are organized by domain, rather than function. Abbreviations should be avoided in namespaces and class names. Legacy code is in the repository root and various subdirectories.

Splitting tests into integration and unit tests
Previously there was no distinction of integration and unit tests. For new code, unit tests should be the main type of tests. Unit tests are placed under  directory matching the namespace layout. There is a Makefile in that directory to easily run all or parts of unit tests while developing.

Type declarations and comments
All new code should declare both parameter and return types. In addition strict types should be enabled using.

Thanks to type declarations, most function and method comments are now redundant, as they would only repeat the parameter names and types. For this reason, linter checks for missing parameter or return type declarations are disabled for code under  and , which roughly correlate with places using type declarations. For this code, do not add redundant documentation unless it provides additional value. One such example is to provide more accurate type hints for array types, for example:

As illustrated above, for comments having only one tag or one line description, do use the one line comment syntax as well.

Constructor dependency injection
New code should have all its dependencies injected via constructor. In many cases this is not yet possible, due to many services only being available in MediaWiki 1.35 (we currently support 1.34 and later) as well lack of ObjectFactory support for services. For such new code, place all dependencies on the class constructor (or main entry point to the class) to easy migration to constructor dependency injection in the future.

File header
For new code, we have chosen the following minimalistic header:

If you wish to assert your copyright more explicitly, you can optionally add @copyright tag as well.

Deprecation and version numbers
When changing Translate code in backwards incompatible ways, do check https://codesearch.wmflabs.org/search/ for any users of the code. Known users are TwnMainPage, TranslateSVG, CentralNotice, MassMessage and bunch of stuff in the translatewiki repo.

You can use the deprecation facilities provided by MediaWiki core, including the @deprecated tag and wfDeprecated hard deprecation. If there are no known users of the code, it is okay to change it in backwards incompatible way without deprecation, unless it is explicitly marked as stable (See Stable interface policy). Code marked as stable should be hard-deprecated at least for one MLEB release.

MediaWiki core version numbers are meaningless in the context of Translate, as Translate always supports multiple MediaWiki releases. Translate itself uses YYYY.MM style versioning (as part of MLEB). New classes and methods should be annotated with @since YYYY.MM tags.