Piracy fix for kwcall

[lgoettgens]

The implementation of #131 does not work properly if the function in question has a kwarg (see the change in the test file here for an example).
This fixes that by ignoring the first two elements of the signature of a kwcall (first is typeof(kwcall) and second is Any, the NamedTuple of all kwargs to be applied), and then considering the third to be "the original function" and everything behind that as positional arguments.

[codecov]

Codecov Report

Merging #171 (9ac8a95) into master (8dc359d) will increase coverage by 0.03%.
The diff coverage is 83.33%.

@@            Coverage Diff             @@
##           master     #171      +/-   ##
==========================================
+ Coverage   77.58%   77.61%   +0.03%     
==========================================
  Files          11       11              
  Lines         736      746      +10     
==========================================
+ Hits          571      579       +8     
- Misses        165      167       +2     

Flag	Coverage Δ
unittests	77.61% <83.33%> (+0.03%)	⬆️

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Files Changed	Coverage Δ
src/utils.jl	92.42% <71.42%> (-2.50%)	⬇️
src/piracy.jl	94.04% <100.00%> (+0.22%)	⬆️

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[fingolfin]

Unfortunately it fails in all older Julia versions (<=1.8)

[lgoettgens]

Unfortunately it fails in all older Julia versions (<=1.8)

Works now in julia 1.5. Let's see if CI succeeds for older version as well. It needed way much more of wiggling around with internals than I expected or wanted.

[fingolfin]

Perhaps it would make sense to use https://github.com/FluxML/MacroTools.jl or https://github.com/invenia/ExprTools.jl instead of rolling this on our own?

julia> ex = :(
                  function Base.f(x::T, y::T; z::Bool=false) where T
                      x + y
                  end
              );

julia> ExprTools.splitdef(ex)
Dict{Symbol, Any} with 6 entries:
  :args        => Any[:(x::T), :(y::T)]
  :body        => quote…
  :kwargs      => Any[:($(Expr(:kw, :(z::Bool), false)))]
  :head        => :function
  :whereparams => Any[:T]
  :name        => :(Base.f)

julia> MacroTools.splitdef(ex)
Dict{Symbol, Any} with 5 entries:
  :name        => :(Base.f)
  :args        => Any[:(x::T), :(y::T)]
  :kwargs      => Any[:($(Expr(:kw, :(z::Bool), false)))]
  :body        => quote…
  :whereparams => (:T,)

[fingolfin]

Ah, but of course that's for expressions, not methods/signatures, so it might not be helpful.

[lgoettgens]

Yeah, these ones unfortunately do not offer what we need here. I couldn't find any good way to test this in other packages. Most just ignore old julia versions, where Core.kwcall doesn't exist, or use some regex with the function name of the kwsorter. The first is not an option here (unless we drop support for julia-pre-1.9, or have different semantics for the tests depending on the julia version). The second option relies on weirder internals, where we won't get good error messages in future changes (as regexes and strings just tell "no", not fail with some type error etc.). Thus, I think the current proposal here is the best we can currently do. I already added a try-catch with some additional debug information for people to open issues here.