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- Subject: Error propagation
- From: "Soni \"They/Them\" L." <fakedme@...>
- Date: Fri, 20 Jul 2018 08:22:02 -0300
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.
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.