seriescolor in recipe is ignored

[yakir12]

@mkborregaard found out that the following doesn't plot in red (this is from my question on Discourse):

@recipe function f(::Type{Val{:home}}, x,y,z)
       seriescolor := :red
       markershape := :star5
       seriestype := :scatter
       x,y
  end

plot(rand(5), st = :home)

[mkborregaard]

I also tried the more specific markercolor, which fails with error message:

Error showing value of type Plots.Plot{Plots.GRBackend}:
ERROR: MethodError: no method matching alpha(::Symbol)
Closest candidates are:
  alpha(::ColorTypes.AGray32) at /Users/michael/.julia/v0.6/ColorTypes/src/traits.jl:11
  alpha(::ColorTypes.ARGB32) at /Users/michael/.julia/v0.6/ColorTypes/src/traits.jl:10
  alpha(::ColorTypes.RGB24) at /Users/michael/.julia/v0.6/ColorTypes/src/traits.jl:9
  ...

[daschw]

The issue is the order in the pipeline in https://github.com/JuliaPlots/Plots.jl/blob/master/src/plot.jl#L219-L236: At first the defaults are applied including matching :auto linecolors etc. with the corresponding seriescolors. Then the seriesrecipe is applied. If this changes e.g. the seriescolor, linecolor still holds the default seriescolor from before.
We could try reversing the order, but it might not be that straightforward and I'm not sure if this could cause other issues.
Otherwise, series recipes really should specify the most specific argument.
@mkborregaard's example from above should be fixed by #1522
However, there's still an issue, for instance, with

gr()
@recipe function f(::Type{Val{:test}}, x,y,z)
       markercolor := 3
       seriestype := :scatter
       x,y,z
end
plot(1:5, st = :test)

markercolor = 3 would be replaced by the 3rd color of the default palette in _add_defaults!, which is however called before the series recipe is processed. Hence gr.jl and finally alpha(c) gets markercolor = 3, which it cannot handle:

plot(1:5, st = :test)
Error showing value of type Plots.Plot{Plots.GRBackend}:
ERROR: MethodError: no method matching plot_color(::Int64)
Closest candidates are:
  plot_color(::Any, ::Void) at /home/dani/.julia/v0.6/PlotUtils/src/colors.jl:15
  plot_color(::Any, ::Number) at /home/dani/.julia/v0.6/PlotUtils/src/colors.jl:18
  plot_color(::Symbol) at /home/dani/.julia/v0.6/PlotUtils/src/colors.jl:6
  ...

We could go along and fix this and similar future issues with separate fix in the way of #1522, but getting the order right might be the more sustainable solution.

[mkborregaard]

Wow, great work @daschw :-O 🎉

[yakir12]

Like assigning "specificity" values to attributes and sorting by that?

[yakir12]

After (my) last update it now works! So I'm closing this 😄

[daschw]

Oh, thanks, yes #1523 should have fixed it 🙂