[BUG] Fix stacktraces on 1.3

[pfitzseb]

No description provided.

[MikeInnes]

1.2 is fairly imminent, so it'd be great to get a fix for this is soon.

[pfitzseb]

Will fix this tomorrow.

[c42f]

I'd suggest that for Juno you should report the entire exception stack in a similar way to Base.show_exception_stack().

This should be an improvement regardless of how we end up fixing JuliaLang/julia#31830

[pfitzseb]

That'd be very different from the REPL, no? Or is the default backtrace printing going to change as well?

Code:

function f(x)
    try
        x//x
    catch err
        throw(ErrorException("haha"))
    end
end
g(x) = f(x)

REPL:

julia> g(0)
ERROR: haha
Stacktrace:
 [1] f(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:10
 [2] g(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:13
 [3] top-level scope at none:0

Base.show_exception_stack():

caused by [exception 2]
haha
Stacktrace:
 [1] f(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:10
 [2] g(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:13
 [3] top-level scope at untitled-7af6d0839891b2927dcc55b4483b0fe7:14
caused by [exception 1]
ArgumentError: invalid rational: zero(Int64)//zero(Int64)
Stacktrace:
 [1] __throw_rational_argerror(::Type) at ./rational.jl:18
 [2] Type at ./rational.jl:13 [inlined]
 [3] Type at ./rational.jl:20 [inlined]
 [4] // at ./rational.jl:43 [inlined]
 [5] f(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:8
 [6] g(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:13
 [7] top-level scope at untitled-7af6d0839891b2927dcc55b4483b0fe7:14

I suppose we could inject the error messages further down the stack into our normal backtrace printing though, so it'd look like:

ArgumentError: invalid rational: zero(Int64)//zero(Int64)
 [1] __throw_rational_argerror(::Type) at ./rational.jl:18
 [2] Type at ./rational.jl:13 [inlined]
 [3] Type at ./rational.jl:20 [inlined]
 [4] // at ./rational.jl:43 [inlined]
haha
 [5] f(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:8
 [6] g(::Int64) at ./untitled-7af6d0839891b2927dcc55b4483b0fe7:13
 [7] top-level scope at untitled-7af6d0839891b2927dcc55b4483b0fe7:14

[c42f]

This is the printing in 1.3-DEV currently:

julia> g(0)
ERROR: haha
Stacktrace:
 [1] f(::Int64) at ./REPL[1]:5
 [2] g(::Int64) at ./REPL[2]:1
 [3] top-level scope at REPL[3]:1
caused by [exception 1]
ArgumentError: invalid rational: zero(Int64)//zero(Int64)
Stacktrace:
 [1] __throw_rational_argerror(::Type) at ./rational.jl:18
 [2] Type at ./rational.jl:13 [inlined]
 [3] Type at ./rational.jl:20 [inlined]
 [4] // at ./rational.jl:43 [inlined]
 [5] f(::Int64) at ./REPL[1]:3
 [6] g(::Int64) at ./REPL[2]:1
 [7] top-level scope at REPL[3]:1

[c42f]

See JuliaLang/julia#30900.

Whether the root cause is printed first or last is a matter of taste. I kind of liked the root cause last so you don't have to go hunting for it by scrolling up too much.

[pfitzseb]

Stacktraces work fine on 1.2-RC, so there's a bit of a grace period to fix this :)