Removing use of Mediawiki’s API ‘rawmode’ in Wikibase

Rawmode was a boolean value used to determine if an API result formatter in Mediawiki needed extra metadata in order to correctly format the result output. The main use of said metadata was in the XML output of the Mediawiki API. How hard can removing it be? This is the story of the struggle to remove the use of this single boolean value from the Wikibase codebase.

Overview

The first commit for this task was made on the 6th July 2015 and the final commit was about to be merged on the 27th August. So the whole removal took just under 2 months.

During this two months roughly 60 commits were made and merged working towards removal.

Overall 9290 lines were removed and 5080 lines were added.

I’m glad that is all done. (This analysis can be found on Google sheets). Sorry there are not more pictures in this post…..

Reason for removal

Well, rawmode is being remove from Mediawiki to remove API complexity. Instead of having to check what the API formatters need they will instead just accept all metadata and simply use what they need and discard the rest.

The change to “Finish killing ‘raw mode'” can be seen on Gerrit and has been around since April of this year. The relevant task can be found on Phabricator.

Process overview

The first step on the path was to remove the old serialization code from Wikibase (otherwise known as the lib serialization code) and replace all usages with the new WikibaseDataModelSerialization component. This component was already used in multiple other places in the code but not in the API due to its reliance on the way the lib serialization code handled the rawmode requirement of the API at the time.

Removal of the lib serialization code was the the first of the two major parts of the process and after around 50 commits I managed to remove it all! Hooray for removing 6000 lines with no additions in a commit…

The next and final step was to make the ResultBuilder class in Wikibase always provide metadata for the API and to remove any dirty hacks that I had to introduce in order to kill the lib code. Again this was done over the course of multiple commits, mainly adding tests for the XML output which at the time was barely tested. Finally a breaking change had to be made to remove lots of the hacks that I had added and the final uses of raw mode.

The final two commits can be seen at http://gerrit.wikimedia.org/r/#/c/227686/ and http://gerrit.wikimedia.org/r/#/c/234258/

Final notes

Look! You can even see this on the GitHub code frequency graph (just….)

You can also find my draft API break announcement post here.

— edit —

It looks like I did break 1 thing incorrectly: https://phabricator.wikimedia.org/T110668 , thought a fix is on it’s way our to the beta site! :)