Merging `layout` scale doesn't work when categories are sorted once

[greimel]

Steps to reproduce

let
	n = 20
	tbl = (; x = rand(n), y = rand(n), grp = rand(["a", "b"], n))

	data(tbl) * mapping(:x, :y,
	    layout = :grp, # VERSION A (works)
	    # layout = :grp => sorter("a", "b"), # VERSION B (errors)
	 ) * visual(Scatter) + mapping(0.5, layout = "b") * visual(VLines) |> draw
end

Error reporting (VERSION B)

MethodError: no method matching isless(::AlgebraOfGraphics.Sorted{String}, ::String)

The function `isless` exists, but no method is defined for this combination of argument types.



Closest candidates are:

  isless(::Missing, ::Any)

   @ Base missing.jl:87

  isless(::Any, ::Missing)

   @ Base missing.jl:88

  isless(::AlgebraOfGraphics.Sorted, ::AlgebraOfGraphics.Sorted)

   @ AlgebraOfGraphics ~/.julia/packages/AlgebraOfGraphics/2kYB2/src/helpers.jl:16

  ...

Images (VERSION A)

Version info

Julia Version 1.11.6
Commit 9615af0f269 (2025-07-09 12:58 UTC)
Build Info:
  Official https://julialang.org/ release
Platform Info:
  OS: macOS (arm64-apple-darwin24.0.0)
  CPU: 11 × Apple M3 Pro
  WORD_SIZE: 64
  LLVM: libLLVM-16.0.6 (ORCJIT, apple-m2)
Threads: 5 default, 0 interactive, 2 GC (on 5 virtual cores)
Environment:
  JULIA_REVISE_WORKER_ONLY = 1

  [cbdf2221] AlgebraOfGraphics v0.11.7
  [336ed68f] CSV v0.10.15
  [13f3f980] CairoMakie v0.15.6
  [324d7699] CategoricalArrays v1.0.1
  [8be319e6] Chain v1.0.0
  [75880514] DataFrameMacros v0.4.1
  [a93c6f00] DataFrames v1.7.1
  [0703355e] DimensionalData v0.29.23
  [0ff47ea0] PlutoLinks v0.1.6
  [7f904dfe] PlutoUI v0.7.71
  [10745b16] Statistics v1.11.1
  [9c32591e] Poppler_jll v24.6.0+0
  [d7dd28d6] tectonic_jll v0.15.0+0
  [44cfe95a] Pkg v1.11.0

[jkrumbiegel]

Yeah the members are fundamentally of a different type in this case and I'm not sure if it makes sense to add special rules to allow merging. Maybe, maybe not. In any case you can sort in a central location via the scales(Layout = (; categories =...)) mechanism.