Hi all,

over the past 1,5 years WMDE’s Technical Wishes team was working on a major improvement of wikidiff2 [1] - the engine behind the wikitext diff view. The major outcome of our improvements got deployed to most wikis just now: It is now easier to find moved paragraphs and text changes inside them. [2]

Why we worked on this:

The idea for the project arose from the wishlist of the German-speaking communities: Show text changes in moved paragraphs. Before we worked on this, moved paragraphs were shown in the diff as a deleted paragraph and then as an added paragraph. This meant that you had to parse visually through the paragraphs to find any potential changes - a fact that vandals liked to make use of. [3]

Desktop version, mobile version

The desktop version of the feature already got deployed to Mediawiki.org and deWP in December 2017. After further improvements of the diff algorithm, the change could now get deployed to most wikis. The languages unified Han, Thai and Japanese that don’t use spaces as delimiters will follow soon. The mobile version is in the making and will follow in the next weeks. The backend work has been done by the WMDE team, the WMF’s mobile team is taking care of the design work for the user interface of the mobile version.

Improving the algorithm of wikidiff2: More than a new feature

The work that has been done goes further than the original wish: First of all, we not only highlighted text changes within a moved paragraph, but also made it easier to find moved paragraphs in the first place: Clickable arrows allow to follow the move of the paragraph. Second, we generally improved the diff algorithm: For example, we could find an old bug in the diff engine: Sometimes two paragraphs which are not related at all were considered a changed paragraph. The bug fix was already deployed in October 2017. [4]

If you are interested in learning more about the work that has been done, we're going to publish the lessons learned by the dev team within the next days (so stay tuned :-) !.

Thank you!

We would like to thank everyone who supported us in the work around wikidiff2: People from different wikis looked into diffs and gave us valuable feedback. Moritz Mühlenhoff supported us by updating the library, and deploying it. Tim Starling and Max Semenik supported us with code review and consultation during the Vienna Hackathon. The Desktop and Mobile Web team is going to add a user friendly design to the mobile version. Your advice, feedback and support is much appreciated :-)

Further feedback is very welcome!

Birgit (for the technical wishes team)

[1] Extension manual: https://www.mediawiki.org/wiki/Extension:Wikidiff2

[2] Deployment ticket: https://phabricator.wikimedia.org/T195375

[3] Main project page on meta: https://meta.wikimedia.org/wiki/WMDE_Technical_Wishes/Show_text_changes_when...

[4] Patch on gerrit for the bug fix: https://gerrit.wikimedia.org/r/#/c/356582/