Updatier: The Mene+Shuman fix now is busted with Firefox 30 and Firebug 2. Firefox 31 may provide workarounds (will investigate). In the meantime, use the “General workaround strategies” listed below.
Update: This answer is now obsolete.
If you open
then you can use Firebug to debug the Greasemonkey script just like any other.
This works irregardless of the
See Mene’s answer — with an assist from Shuman.
Because Greasemonkey operates in a sandbox, Firebug cannot see it. There is no easy way around this.
General workaround strategies:
Test all parts of a GM script that don’t use
GM_functions and don’t use
All of Firebug’s
consolefunctions work great from within a GM script.