Juno debugger stops at `@unpack` from Parameters

General Usage
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1

I am using the Parameters package v0.12.0 by @mauro3 in my numerical simulations. While using the Juno debugger in JuliaPro, I noticed that the debugger stops when reaching a call to Parameters’ @unpack. Below is a MWE:

# MWE.jl
using Parameters

@with_kw struct A
    a::Int = 6
end

function testA(varA::A)
    @unpack a = varA
    # a = varA.a
    print(a, '\n')
end

Everything is working fine when running

julia> include("MWE.jl")
julia> testA(A())
julia> Juno.@enter testA(A())

up to the last line. This debugging statement opens @unpack in debug mode (Parameters.jl, stopping at line 751: $kdblock), which becomes annoying when debugging a big code with several such calls. Note that the same MWE where @unpack a = varA is replaced by a = varA.a behaves fine (but it’s less convenient).

Question: is there a way to avoid that the debugger stops at @unpack?

I am using JuliaPro 1.4.1-1 (Julia 1.4.1, Atom 1.45.0, julia-client 0.12.4) on Windows 10, but observed the same behavior on previous versions too.

Edit: Similar behavior with the @unpack macro from UnPack.jl, by writing using UnPack and

# MWE.jl [...]
    UnPack.@unpack a = varA

Edit: Also same behavior with a breakpoint located at print(a, '\n'), and with the command

julia> Juno.@run testA(A())
2

That is odd. But I’m not using Juno, so I cannot easily help here. One thing you should try is whether this also happens when using @unpack directly from UnPack.jl.

2 Likes
3

The Juno debugger does step into the expanded macro, yes. This is by design.

I’d suggest setting breakpoints at wherever you want to actually stop and start stepping through the code from there (also need to use Juno.@run testA(A()) or the Debug: Run Block command).

2 Likes
4

Thanks for support. The MWE

# MWE.jl
using Parameters
using UnPack

@with_kw struct A
    a::Int = 6
end

function testA(varA::A)
    UnPack.@unpack a = varA
    # a = varA.a
    print(a, '\n')
end

has the same behavior (Juno debugger steps into the macro @unpack from UnPack.jl and stops at the same line). Might be a Juno feature.

5

Thanks for support. I tried Juno.@run testA(A()) with a breakpoint at the line print(a, '\n'), but the behavior is the same. Juno debugger steps into Parameters.jl, and is stuck in that source file. Continuing debug session works, but then breakpoints in MWE.jl are ignored. (Everything is still working fine when @unpack a = varA is replaced by a = varA.a – which are supposed to behave in a similar way).

6

Ah, true. The problem is that the @unpack macro expands to ~12 lines of code, so breakpoints on the next few lines actually stop you in @unpack.

The best solution right now is probably to use JuliaInterpreters @bp macro like

function testA(varA::A)
    @unpack a = varA
    @bp
    println(a)
end

Juno.@run testA(A())
3 Likes
7

Yes, using @bp allows to continue debugging after Juno’s debugger stepped into @unpack. Thanks!

8

You can continue debugging even when you are in @unpack by doing a few (or more) Step Expr steps.