Error propagation

["Soni \"They/Them\" L." <fakedme@...>]

I noticed there doesn't seem to be any way to propagate errors "caught" 
with pcall/xpcall/lua_pcall. Why is this the case?

Throwing an error from the error handler isn't an option, as Lua eats 
those, and calling error() isn't an option as Lua eats the backtrace in 
that case. It would be nice to see a return value used to indicate 
whether to "keep unwinding" or just eat the error.[1][2]

Nested pcalls with "keep unwinding" set would give access to the full 
backtrace to all pcalls. That is, if you have 3 propagating pcalls then 
1 eating pcall, they'd all have their error handlers called before the 
error unwinds the stack. Returning a new error object would use the new 
error object for future error handler calls. Error handlers would be 
called in reverse order. Erroring in non-propagating error handlers 
would just, uh, so like there are 2 ways to do this: restart the error 
handling from the top of the stack, or restart from the erroring error 
handler. I'm not sure which one would be "more correct" but I'd probably 
go with the latter.

Other languages don't do this - they print errors as soon as their 
equivalent of error() is called.[3]

[1] https://www.lua.org/manual/5.3/manual.html#2.3

[2] https://www.lua.org/manual/5.3/manual.html#lua_pcall

[3] https://doc.rust-lang.org/std/panic/fn.set_hook.html