I accidentally deployed a dodgy bit of code to one of my function apps. Then, even when I tried to revert to a “known good” version of my code via the GUI, it still didn’t work. No matter what I did, I kept getting the dreaded “Compilation Failed” error – but there was no more information. No useful compilation errors…

2016-10-23T20:35:46.853 Function started (Id=5ededb27-6144-40d1-8d14-8db77d70b771)
2016-10-23T20:35:47.901 Function compilation error
2016-10-23T20:35:47.901 Function completed (Failure, Id=5ededb27-6144-40d1-8d14-8db77d70b771)
2016-10-23T20:35:48.369 Exception while executing function: Functions.fetchDepartureBoardOrchestrator. Microsoft.Azure.WebJobs.Script: Script compilation failed.

It was so frustrating. Until I worked out that you can actually restart the power app host – just go to the Function App Settings then click “Go To App Service Settings” at the bottom.  You’ll see the traditional “full” properties and settings blade, and at the top is a “Restart” button. Then I was able to save my updated code.