Update: One day after I wrote this post, version 2.8.36 was released to fix this problem. It seem that other versions of Symfony were also affected. If you are interested in this problem, read on. If you are affected by it, you should upgrade, not use the fix from here.
Last night I implemented a few improvements in the Metadiscourse annotator which I am developing in my spare time. (I rewrote several functions that cut the running time of two actions from minutes to seconds … but that’s for a different post, maybe …). I tested the new code on my development computer and everything seemed perfect, so I deployed the new version. Just before sending an email to the people who use this program, I noticed that a particular functionality that relied on AJAX requests no longer worked. This was completely unrelated to the changes I made. Initially, I thought it is because I restricted the HTTP method to GET, whilst the request was done using POST. I fixed that, but it was still not working. After spending a bit of time, I realised that none of the AJAX requests worked anymore. This was at 1am, how else 🙂