Flow uses a synchronous XMLHttpRequest. These should be avoided since it blocks waiting for a network response, and can create a bad UX.
For this reason, it's been actively deprecated in recent Firefox (30+), when used on the main thread (https://developer.mozilla.org/en-US/docs/Web/API/XMLHttpRequest), and will log a warning.
It is used in mw.flow.parsoid.convert. This in turn is called twice, both from ext.flow.editor.js:
- mw.flow.editor.load - https://git.wikimedia.org/blob/mediawiki%2Fextensions%2FFlow/a4eda372ccbd733ff741d3e1369c25a1e561fcf0/modules%2Feditor%2Fext.flow.editor.js#L88 - This is using promises already, so it should be straightforward to use an async call here.
- mw.flow.editor.getContent - https://git.wikimedia.org/blob/mediawiki%2Fextensions%2FFlow/a4eda372ccbd733ff741d3e1369c25a1e561fcf0/modules%2Feditor%2Fext.flow.editor.js#L88 - This is synchronous, and used by FlowBoardComponent.UI.events.globalApiPreHandlers.prepareEditor. For this one, it also seems like it would be better to do the HTML->wikitext conversion on the server if possible, rather than round-trip a XHR call then post.
Version: master
Severity: normal