[lua] Unused `__lua_lib_lrexlib_Rex = _G.require("rex_pcre")` in output leads to "module rex_pcre not found" error

[martinluetke]

Haxe Compiler 4.0.0 (git build development @ 085f38e)

I found this unsused line in my main.lua:

__lua_lib_lrexlib_Rex = _G.require("rex_pcre")

It breaks my script as I dont have that requirement around.
__lua_lib_lrexlib_Rex is apparently not used anywhere within my result lua script and removing that line fixed my problem. My actual workaround is to add an empty "rex_pcre.lua" file next to my script.

I dont know what that module does (please excuse my ignorance), but if it references libpcre-1.dll in my haxe installation folder, I can not have it! Factorio does not allow anything but plain lua imports.

[jdonaldson]

I might need @Simn 's help on this. It looks like a dce issue. (the require for rex_pcre will get generated even with a simple "hello world" application).

I poked around on dce.ml for a bit, but didn't find anything obvious.

[Simn]

DCE doesn't remove extern classes, so your @:luaRequire("rex_pcre") on the Rex class always makes it to the generator. Maybe put it on EReg instead?

[nadako]

Hmm. If @:directlyUsed is added even though the type doesn't appear in the output, then there's surely something wrong with the DCE. Maybe it's some processing order issue, e.g. it first marks Rex as directly-used when it encounters that static var FLAGS : Table<String,Int> = Rex.flags(); and then it removes the FLAGS. I can try looking into that when I get a minute.

[nadako]

Should be fixed now. Not sure how to add a test for that though.

The problem was caused by the Rex.create method that references Rex in its body, so the class was marked as directly used even though it wasn't actually used outside of itself. I added a check for dce.curclass so it doesn't mark a class directly used if it's used within its own methods. That sounds logical to me.

[jdonaldson]

Good catch. I could've dropped the reference in this case, but I imagine this can happen when folks try to do custom inline constructors/builders for their extern instances.