Weird init_by_lua* behaviour around empty tables, nils, arguments in general.

[datafatmunger]

The easiest way to reproduce "weirdness":

init_by_lua 'print({})';

Will produce:

nginx: [error] init_by_lua error: init_by_lua:1: bad argument #1 to 'print' (string, number, boolean, or nil expected, got table)
stack traceback:
[C]: in function 'print'
init_by_lua:1: in main chunk

Strange because this works outside of Nginx fine, and even seems to work in content_by_lua.

Specifically in my case, I have similar weirdness:

local upvalues = self:readObject()
for index,upvalue in ipairs(upvalues) do
   if typeidx == LEGACY_TYPE_RECUR_FUNCTION then
      debug.setupvalue(func, index, upvalue)
   elseif upvalue.name == '_ENV' then
      debug.setupvalue(func, index, _ENV)
   else
      debug.setupvalue(func, index, upvalue.value)
   end
end

Results in:

nginx: [error] init_by_lua_file error: ...g/Development/torch/install/share/lua/5.1/torch/File.lua:241: bad argument #1 to 'ipairs' (table expected, got nil)
stack traceback:
    [C]: in function 'ipairs'

Again, code works fine outside of init_by_lua*

[membphis]

init_by_lua 'print({})';

https://github.com/openresty/lua-nginx-module#print
syntax: print(...)

Writes argument values into the nginx error.log file with the ngx.NOTICE log level.

if you put the print({}) to the content_by_lua, you should set your log level to notice level as blow, then you'll get the same error message.

error_log logs/error.log  notice;

for the second case, the error log have said clear very mush, the var upvalues is nil, please resolve this at first.

[agentzh]

@bgraves print({}) is invalid in content_by_lua too:

2015/12/04 15:13:17 [error] 13704#0: *1 lua entry thread aborted: runtime error: content_by_lua(nginx.conf:46):2: bad argument #1 to 'print' (string, number, boolean, or nil expected, got table)

Please try harder to provide a minimal and self-contained test case that actually works inconsistently. Thank you :)

BTW, ngx_lua overrides print as documented here:

https://github.com/openresty/lua-nginx-module#print

The behaviour is not identical to the standard Lua language's version.