How to override print function about luvi

[creationix]

yes, you can set _G.print to override it. I do this in the luvit pretty-print package. https://github.com/luvit/luvit/blob/master/deps/pretty-print.lua#L295-L304

[LoganDark]

it seems that pcall(func) does not use _G. is that true?

[LoganDark]

if it is, how to I pcall a function while allowing access to _G?

[LoganDark]

@creationix

[creationix]

pcall should work. See also http://www.freelists.org/post/luajit/pcallxpcall-broken-in-v21-if-JITed

[creationix]

FWIW, I released a new luvi, lit, luvit, and friends yesterday that has the fix from luajit mentioned in that post. Try again after updating just in case that was the problem.

[LoganDark]

The issue is a function called with pcall can't access the functions I define before running it

[creationix]

How are you defining them?

[LoganDark]

Thru _g and normally

[creationix]

How exactly? There is no such global _g, the case matters.

In other words, share a snippet of code that reproduces the problem. Luvit obviously customizes print globally and it works great. So we know it's possible, but something is wrong with your code.

[LoganDark]

I meant _G

[squeek502]

Perhaps unlikely, but make sure the function's environment is not being changed (by setfenv) before it gets pcall'd. For example, this would cause the problem you're talking about:

local oldprint = _G["print"]
_G["print"] = function(...) oldprint("New print called") end

local callee = function()
    print("This shouldn't print")
end

setfenv(callee, {print = oldprint})
pcall(callee)

running that would output:

> lua test.lua
This shouldn't print