Tables with __tostring metamethods lead to infinite yield

[CompeyDev]

Summary

With tables that have a __tostring metamethod that invokes stdio.format, a mutex deadlock within the formatter is triggered, causing an infinite yield.

Minimal Reproduction

local stdio = require("@lune/stdio")

local a = {}
setmetatable(a, {
    __tostring = function()
        return stdio.format(5)
    end,
})

print(stdio.format(5)) -- prints immediately
print(a) -- yields infinitely

Root Cause

This behavior occurs due to the mutex guard here:

lune/crates/lune-utils/src/fmt/value/mod.rs

Line 51 in c935149

let _guard = COLORS_LOCK.lock().unwrap();

This guard exists to prevent sudden changes in global coloring configuration in the console crate, which can cause unexpected coloring behavior.

The print method calls the formatter, which calls a __tostring implementation if present, and the metamethod calls stdio.format again -- bam! Infinite recursion.

Potential Fixes

• Trivially replace the Mutex with an RwLock and prevent this deadlock
• File an issue with console-rs to make color configuration non-global