Revert "Don't expose Go timers directly to lua"

[dmaluka]

This reverts commit 4ffc220.

Reason for revert: some plugins happen to use raw Go timers via time.AfterFunc(), in an unsafe way (without synchronizing their async code with micro). Let them keep doing that for now, in an unsafe way but at least without immediate crashes.

Fixes #3209

[JoeKar]

Shall we wrap it and add deprecation warning?
In case no, then it can immediately being merged.

[dmaluka]

Shall we wrap it and add deprecation warning?

I can't see how. Lua is an interpreted language, all errors/warnings are runtime. Do we want users of those plugins to see a "this API is deprecated" warning every now and then?

[JoeKar]

Lua is an interpreted language

Well, right. So It would only be possible by exposing an Lua function including --- @deprecated.
But to be honest, I don't know if it will cause what I expect it to do, since I don't use Lua that often.

In case it isn't worth the effort then forget my idea.
Hopefully we remember then, that the support shall be dropped.

[dmaluka]

I don't use Lua often either, I don't know what is @deprecated (can't see anything about it in https://www.lua.org/manual/5.4/manual.html ?), so I don't quite understand what is your idea about.

[taconi]

Maybe something like this:

  L.SetField(pkg, "AfterFunc", luar.New(L, func(d time.Duration, f func()) *time.Timer {
    log.Println("The 'AfterFunc' function will be removed in version 2.0.15")
    return time.AfterFunc(d, f)
  }))

But I believe this log will only be seen run with -debug and examine the log.txt

[dmaluka]

But I believe this log will only be seen run with -debug and examine the log.txt

Yep.

Hopefully we remember then, that the support shall be dropped.

Pushed 4718c98 with a TODO, so that we are a bit less likely to forget.

Actually, I'd be even fine if we keep these raw APIs around forever (undocumented though). Let people shoot themselves in the foot if they prefer to.

[JoeKar]

I don't know what is @deprecated (can't see anything about it in https://www.lua.org/manual/5.4/manual.html ?), so I don't quite understand what is your idea about.

Ok, then my search results are misleading and I've to excuse.

Explicit deprecated functions within the Lua src are only commented:

src/lauxlib.h:** Compatibility with deprecated conversions
src/lstate.c:** Deprecated! Use 'lua_closethread' instead.
src/lstrlib.c:    case 'z' : res = (c == 0); break;  /* deprecated option */
src/luaconf.h:@@ LUA_COMPAT_MATHLIB controls the presence of several deprecated
src/lmathlib.c:** Deprecated functions (for compatibility only)
src/lua.h:LUA_API int        (lua_resetthread) (lua_State *L);  /* Deprecated! */

So forget my thoughts. Separating and marking them with the TODO is feasible enough.