Fix show for const properties of type Vector or Symbol (#29)

* fix access to empty vector for const fields

* trigger CI

* fix syntax error and printing of symbols

* don't print in tests

---------

Co-authored-by: Simon Christ <SimonChrist@gmx.de>

src/ProtoStruct.jl

@@ -161,7 +161,7 @@ macro proto(expr)
  end
 
  function Base.show(io::IO, o::$name)
- vals = join([x[] isa String ? "\"$(x[])\"" : x[] for x in getfield(o, :properties)], ", ")
+ vals = join([x isa Base.RefValue ? (x[] isa String ? "\"$(x[])\"" : x[]) : x for x in getfield(o, :properties)], ", ")
  params = typeof(o).parameters[1:end-$N_any_params-1]
  if isempty(params)
  print(io, string($name), "($vals)")

test/test_ProtoStruct.jl

@@ -153,13 +153,15 @@ end
  const B = :no
  const C::T = 3
  D
+ const E::Vector{Int} = Int[]
  end
 
  @testset "const fields" begin
  cf = @test_nowarn WithConstFields(D = 1.2)
  @test cf.A == 1
  @test cf.B == :no
  @test cf.C == 3
+ @test_nowarn show(devnull, cf)
  cf.A = 5
  @test_throws ErrorException cf.B = :yes
  @test_throws ErrorException cf.C = 5