Since the seed is not reset, math.random() can be used to propagate a global state between indenpendent module invocations, which should be avoided.
Example: http://fr.wikipedia.org/w/index.php?title=Module:Sandbox&oldid=101826839
Version: unspecified
Severity: normal
Since math.random is supposed to be an interface to the C rand() function,[1] and that function is explicitly defined as being seeded with 1 if srand (math.randomseed) hasn't been called,[2] I'd suggest fixing this by calling math.randomseed( 1 ) at the top of mw.executeFunction() (in engines/LuaCommon/lualib/mw.lua).
If no one objects in a reasonable period of time (and no one beats me to it), I'll submit a Gerrit change to do this at some point in the not-too-distant future.
[1]: http://www.lua.org/manual/5.1/manual.html#pdf-math.random
[2]: http://manpages.debian.net/cgi-bin/man.cgi?query=rand&sektion=3&format=html
After thinking about it again, this probably requires some extra care in case of nested modules invocations. Otherwise, the random generator might be unexpectedly reset when frame:expandTemplate() is called, for instance.
(In reply to orlodrim from comment #2)
After thinking about it again, this probably requires some extra care in
case of nested modules invocations. Otherwise, the random generator might be
unexpectedly reset when frame:expandTemplate() is called, for instance.
Good catch!
Change 122862 had a related patch set uploaded by Anomie:
Prevent passing information between #invokes using math.random
Change 122862 merged by jenkins-bot:
Prevent passing information between #invokes using math.random