Because stderr is set to null by default, all error output from lua is lost. This is probably good for production, but when someone is just setting up Scribunto initially (the case where they are least likely to know how to change the error output), they expect errors in the web server's log.
Version: master
Severity: normal
Or they could just read the extension's documentation for how to install, configure, and troubleshoot it.
Note that the output from the standalone interpreter is copious even in the absence of errors. I doubt people would be particularly happy with their logs being flooded with this information.
"How do I turn off this noise from lua?" is a much better FAQ than "Lua doesn't work and I don't see any errors. What is going on?"
Errors should be easily discovered.
Change 75988 had a related patch set uploaded by MarkAHershberger:
Scribunto should send lua error output to error log
I did see the debugging cruft that the lua wrapper puts in, but managed to elide it unless debugging information is requested.
Change 75988 abandoned by MarkAHershberger:
Scribunto should send lua error output to error log