Better Layer printing

Project.toml

@@ -1,7 +1,7 @@
 name = "AlgebraOfGraphics"
 uuid = "cbdf2221-f076-402e-a563-3d30da359d67"
 authors = ["Pietro Vertechi", "Julius Krumbiegel"]
-version = "0.7.1"
+version = "0.7.2"
 
 [deps]
 Colors = "5ae59095-9a9b-59fe-a467-6f913c188581"

src/algebra/layer.jl

@@ -512,3 +512,19 @@ function compute_attributes(pl::ProcessedLayer,
     # remove unnecessary information
     return filterkeys(!in((:col, :row, :layout, :alpha, :group)), attrs)
 end
+
+function Base.show(_io::IO, l::Layer; indent = 0, index = nothing)
+    io = IOContext(_io, :limit => true)
+    ind = "  " ^ indent
+    printstyled(io, ind, "Layer ", index === nothing ? "" : index, "\n", bold = true)
+    println(io, ind, "  transformation: ", l.transformation)
+    println(io, ind, "  data: ", typeof(l.data)) # print only type here as data source could be anything and print a lot of stuff
+    println(io, ind, "  positional:")
+    for (i, pos) in enumerate(l.positional)
+        println(io, ind, "    ", i, ": ", pos)
+    end
+    println(io, ind, "  named:")
+    for (name, named) in pairs(l.named)
+        println(io, ind, "    ", name, ": ", named)
+    end
+end

src/algebra/layers.jl

@@ -453,4 +453,13 @@ function to_entry(P::Type{Heatmap}, p::ProcessedLayer, categoricalscales::Dictio
     ]
 
     Entry(P, positional, merge(p.named, p.primary, p.attributes, color_attributes))
+end
+
+function Base.show(io::IO, layers::Layers; indent = 0)
+    ind = "  " ^ indent
+    printstyled(io, ind, "Layers", bold = true)
+    println(io, ind, " with $(length(layers.layers)) elements:")
+    for (i, layer) in enumerate(layers)
+        show(io, layer; indent = indent + 1, index = i)
+    end
 end

test/algebra.jl

@@ -131,4 +131,17 @@ end
     @test processedlayers[6].positional[1] == exp.(df.x[df.c .== "c"])
     @test processedlayers[6].positional[2] == df.z[df.c .== "c"]
     @test processedlayers[6].named[:markersize] == df.w[df.c .== "c"]
-end
+end
+
+@testset "printing" begin
+    spec = data((; x = 1:10, y = 11:20)) * mapping(:x, :y, color = :y) * visual(BarPlot) + mapping(:x) * visual(HLines)
+    # testing printing exactly is finicky across Julia versions, just make sure it's not completely broken
+    printout = @test_nowarn repr(spec)
+    @test occursin("Layers with 2 elements", printout)
+    @test occursin("Layer 1", printout)
+    @test occursin("Layer 2", printout)
+    @test occursin("transformation:", printout)
+    @test occursin("data:", printout)
+    @test occursin("positional:", printout)
+    @test occursin("named:", printout)
+end