MediaWiki Introduction 2023

MediaWiki Introduction 2023 is a 3-part video series by Timo Tijhof, recorded in December 2023 for the MediaWiki Code Jam.

Part 1: MediaWiki core concepts

Watch on Wikimedia Commons. • Watch on YouTube

Timestamps:

00:00 Outline
00:50 Database schema
01:37 Users
02:55 Preferences
04:12 Localisation
05:02 Permissions
08:50 Bot passwords
10:10 Logging
11:58 Comments
12:35 Recent changes
15:39 Pages
16:00 Namespaces
18:14 Revisions
18:20 Example: Save an edit
19:59 Example: View a page
20:52 Link tables
21:02 Categories
24:20 Templates
25:05 Image links
25:59 GLAM
26:43 External links
27:40 Statistics
28:02 Search
29:14 JobQueue
31:58 Multimedia

High-level product and architecture perspective. Component walk-through.

• Database layout
• Who writes Wikipedia
• Why create an account
• CSSJanus docs
• CSSJanus demo
• Permissions
• Change user rights
• Bot passwords
• Logging
• No original research
• Recent changes
• RCFeed
• Listen to Wikipedia
• CodePen
• ClueBot
• Namespaces
• Special pages
• Page table
• Revision table
• Text table
• External storage
• Example category
• Everything is a wiki page
• GLAM
• Glamorous tool
• Example photo
• Statistics
• JobQueue
• MediaWiki Engineering - Performance practices
• Multimedia

Part 2: Wikipedia's extensions

Watch on Wikimedia Commons. • Watch on YouTube

Timestamps:

00:00 Outline
00:25 What is an extension?
01:52 How to install an extension?
02:01 Install WikiEditor
02:54 Install VisualEditor
03:58 Wikipedia's extensions
04:10 CentralAuth
04:38 Echo
04:56 OAuth for MediaWiki
05:40 Editor extensions
05:48 Parser extensions
06:37 Cite extension
07:37 EasyTimeline
07:56 InputBox extension
08:38 Scribunto
09:38 Faster editing performance
11:24 Media handlers
11:31 TimedMediaHandler
11:42 3D extension for MediaWiki
11:57 Spam prevention extensions
12:35 Gadgets
13:05 Gadget demo
13:41 Gadget examples

What is an extension?

How to install an extension in two easy steps.

Walk-through the installed extensions via Wikipedia's Special:Version page.

• What is an extension
• WikiEditor extension
• VisualEditor extension
• Wikipedia's extensions
• CentralAuth
• Echo
• Cite
• EasyTimeline
• EasyTimeline example: Version lifecycle
• InputBox
• InputBox example: Incident status
• Scribunto
• Lua example: SchemaDiagram
• What Lua scripting means for Wikimedia (2013)
• How we made editing Wikipedia twice as fast (2014)
• Save Timing in Grafana
• TimedMediaHandler
• 3D extension
• AbuseFilter
• Gadgets
• Gadget example: RTRC
• Gadget example: Stockphoto
• Half-timbered mansion, by Radomianin

Part 3: Write an example patch

• Homework preparation:
  • Quickstart.
  • Run PHPUnit, e.g. composer phpunit -- tests/phpunit/includes/ResourceLoader/
  • Run QUnit, e.g. view http://localhost:4000/index.php/Special:JavaScriptTest
  • Clone the "examples" repo in your extensions/ directory, and enable it.
• How does an extension actually work?
  • Manual:Extension registration (wfLoadExtension loads extension.json)
  • Manual:Extension.json/Schema ("type", "SpecialPages" is a registry, "AutoloadNamespaces" is a registry).
  • Best practices for extensions (keep it simple, reduce decisions/choices, fewer things to verify, "includes/").
  • Manual:Coding conventions/PHP (quick open, file name = class name)
• How do special pages work?
  • MediaWiki takes care of URL routing.
  • File:MediaWiki_infrastructure_2022.png
  • MediaWiki at WMF
  • MediaWiki loves registries that do things for you automatically. MediaWiki constructs your SpecialPage class, and skins the output.
  • Special:SpecialPages.
  • Special:HelloWorld -> execute, now it's our turn.
  • OutputPage
  • RequestContext->msg
• Localisation
  • uselang=qqx (debugging, contributions, Translatewiki.net)
  • Help:System message
  • i18n/en.json (git-grep, "MessageDirs")
• Excercise 1: Edit a localisation message. Change the "example-helloworld" message and notice the change on Special:HelloWorld.
• Excercise 2: Create a new localisation message, and output it on Special:HelloWorld.
• Hooks
  • extension.json ("Hooks" is a registry, "HookHandlers" is a registry)
  • MediaWiki will call Hooks.php#onSomething, now it's our turn.
  • Manual:Hooks
  • BeforePageDisplay
  • $wgExampleEnableWelcome (extension.json, "config" is another registry)
  • Namespaces (remember from Part 1)
• Excercise 3: Make a config change. Edit LocalSettings.php to disable $wgExampleEnableWelcome and notice the change on Main_Page. Comment your edit to re-enable it.
• Excercise 4: Edit a hook handler. Make it welcome you on special pages instead of articles. Notice the change on Special:HelloWorld and Main Page.
• ResourceLoader
  • extension.json ("ResourceModules" is another registry, "dependencies", "packageFiles")
  • ResourceLoader/Developing with ResourceLoader
  • onBeforePageDisplay, OutputPage::addModule.
  • welcome.js
  • styles.css
  • Special:JavaScriptTest?filter=welcome
  • ext.Example.welcome.test.js
• Excercise 5: Improve test and fix the bug. The welcome message greets you with the wrong day. Improve the QUnit test by using strictEquals. Copy the actual value from Special:JavaScriptTest and set it as the expected, except with the correct day. The test should now fail. Try to fix this bug in welcome.js, and notice the tests passing afterwards. Also verify that it works correctly on the Main Page.
• Save your change and upload it to Gerrit:
  • git add -p
  • git commit
  • git-review.
  • Gerrit.
  • WMF CI: Jenkins build output.