Logging errors in SamlauthEvents::USER_SYNC

It would surprise me. The SamlauthEvents::USER_SYNC event is just dispatched in the middle of a long login procedure, which logs & throws exceptions for all over the place.

So yes, your log should be logged. In fact the message in your RuntimeException should always get logged too.
(The code is horrible to read because Drupal Core + Redirects == horrible side effects that need to be protected against... but... your exception should end up being passed to SamlController::handleExceptionInRenderContext(), which basically always should log the message.)

So in short, I don't know what's going on there.

Oh, what I said isn't true. If you set the 'error_throw ' / "Bypass error handling'" config to TRUE, that method doesn't log.

If that setting influences your message being logged, I'd like to know because then I need to do more testing / documenting.

Thank you so much @rodrik for that quick response.

If I check "Bypass error handling" the effect is that the RuntimeException is not logged. But no effect on the call to error log, whether its Bypassed or not. When unchecked the exception is logged, but not the logger error.

No matter how, I cant seem to log en error in my callback with $this->logger->error, if I throw an exception afterwards.

OK, the effect on the RuntimeException is as expected, I guess.

But this makes the weirdness more glaring. the RuntimeExcption message is logged, and that's just being done (in handleExceptionInRenderContext()) by some $this->logger->warning(), which should be completely equivalent to the log call you are doing. So why your earlier message is not logged just before that moment, is even more mysterious to me.