Biggest mustache. ⚓ T249673 RFC: A modern and restrictive (but flexible!) skin system using Mustache

Affected components: Skin, TemplateParser, Selected(and stable) skins: Modern/CologneBlue/Monobook, potentially API Modern mustache.

Engineer(s) or team for initial implementation: (Ideally) Core Platform + Web


There is dissatisfaction with the existing skin system. I recently documented this in a blog post Why does building a skin require PHP knowledge?

As far as I can see the main issues being:

It’s difficult to create a new skin unless you have a wide range of skills including knowledge of PHP and backend technologies as well as mediawiki internals

Deploying an existing skin into production adds a huge maintenance burden given the lack of boundaries to the skin system

It is difficult to integrate extensions with existing skins which do not share a common markup or API for key interface elements.

We have a few 'official' and modern looking skins released in the tarballs and very few skin developers

Most mediawiki instances are using the Vector skin and sharing look and feel with other sites because of the above reasons

Who am I?

I have 8 years of experience of writing skins for MediaWiki full time. I built the Minerva skin and am now working on the desktop refresh. I’ve hit many of the issues with the existing skin “architecture” and exploited the lack of boundaries in the development of Minerva.

Having grown up in the Myspace and Tumblr generation, I’ve seen first hand at what is possible when you lower the barrier for entry for would-be developers. My theory is that by removing the need to know PHP we will open ourselves up to a larger audience of skin developers.

TODO: Add data around skillset availability for PHP+CSS+JS vs CSS+JS.

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1. a skin can be built without php

It should be possible for a skin to be declared as being a modern Mustache skin without extending a PHP class

It should be possible to create a skin using only the JSON, CSS (or LESS), Mustache (HTML) technologies.

A skin can optionally use JS and PHP if necessary.

2. A stable skin API

Flexible template data that is subject to a strict and stable skin API is sent to the Mustache template. This template data will use a PHP unit test to enforce the following rules:

Any HTML will be prefixed with

Any data will be prefixed with

The template data will be subject to the deprecation policy.

Mustache/TemplateParser will emit warnings if template keys that don't exist are used (see T128864 )

Template keys that are deprecated will emit deprecation warnings using the solution for T128864

The data can be modified by the appropriate constrained hooks

3. autodiscovery of assets

A skin declared as a Mustache skin will automatically have a stylesheet associated with it that is provided by the ResourceLoader module `skins.<skinkey>". If none is defined then the skin will appear unstyled.

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A Mustache skin will automatically add a ResourceLoader module `skins.<skinkey>.scripts" as its JavaScript entry point. If none is defined the skin will be assumed to have no JavaScript code

A skin declared as a Mustache skin must declare a template at the path


If no template is found a RuntimeException will occur.

A skin may use template partials if wanted. They can use arbitrary names.

4. restrictions and constraints

Skins using the Mustache render will no longer be able to declare their own hooks other than those provided by core. This will keep the skin API scoped. Extensions wanting to target skins are free to check skin name inside hooks.

Skins are encouraged to use i18n. Skins will be able to use template keys prefixed with

which will be automatically provided during template rendering.

Reduce the amount of hooks that a skin needs to integrate with. The hooks will deal with data rather than output and will be strengthened to meet existing extension requirements.

We will implement a Mustache based skin architecture that matches the specification

The new skin API is documented and stable.

Beard and mustache style 2016

We will rewrite Modern, Cologne Blue and Monobook in the new system to simplify their code using the new skin API.

The ExampleSkin is deprecated and updated to point to a skin generator based on which will generate frontend only scaffolding for a skin with updated best practices.

We will create a healthier skin ecosystem.

We will have a more maintainable skin ecosystem.


Proof of concept:

The following two patches should hopefully capture the vision here

The fully functional Skinomatic tool should hopefully showcase the power of utilizing the underlying technologies (be sure to click build button in top right and try the resulting zip file in your MediaWiki instance!


what about Vue.js?

Mustache is currently in core so this is why I am using it. My main focus is abstraction. In future it should be very straight forward for a skin to define a Vue based template using rather than skinname.mustache. I will be keeping tabs on the work there particularly around server side rendering to make sure the new skin system is agnostic to templating language.

Further Inspiration
Overall rating page: 4.3 / 5 left 1230 people.

Posted by at 01:46AM

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