Request for Comment/Hybrid extension management

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Over the last years there have been several attempts to use the Composer "package manager" as a way to manage MediaWiki extensions. At the moment there are already a lot of extensions that support Composer as a way of installing and updating.

The main concerns about using Composer as an extension-management-tool is that Composer "is for managing libraries, not extensions" and that extensions would bypass wfLoadExtension(). This second part was a special concern for multiple wikis hosted from the same codebase (i.e. wikifarms).

Proposal

The responsibility of "managing" extensions should be split up between Composer and MediaWiki's ExtensionRegistry. It would become a "hybrid system".

  • Composer is responsible to download and update extensions and their libraries
  • ExtensionRegistry is responsible to check for inter-extension-dependencies as well as for version contraints (e.g. to the core MediaWiki version)

This means that an incompatible version can be installed by Composer but ExtensionRegistry would not enable it.

  • composer.json => Evaluated at "installtime"
  • extension.json => Evaluated at "runtime"

The current situation can easily be improved by some minor policy and software changes:

  1. Extensions must not enable themselves automatically via installation by Composer (e.g. by autoload.files)
  2. Extensions must only declare dependencies to libraries in the composer.json. All dependencies to MediaWiki core versions and inter-extension-depenencies must be declared in the extension.json (By this, a virtual MediaWiki package is not required).
  3. The WMF should not just allow, but encourage the use of "packagist-compatible" (must have fields like name, type and extra.installer-name) composer.json files in the extension repositories. This should be the case for all actively supported branches (LTS) of the WMF owned extensions.
  4. MediaWiki's ExtensionRegistry must not break the wiki in case the requirements declared in extension.json (field requires) could not be met. Instead it should leave the extension disabled, log the issue and put out a proper message to the user/admin (e.g. in a section "Loaded but not enabled extensions" on "Special:Version")

See also

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