Add custom subtypes function to avoid deprecation warnings

src/libmagickwand.jl

@@ -122,7 +122,42 @@
   "Oklch"
 ]
 const IMColordict = Dict([(IMColorspace[i], i) for i = 1:length(IMColorspace)])
-for AC in vcat(subtypes(AlphaColor), subtypes(ColorAlpha))
+
+# See the discussion of https://github.com/JuliaIO/ImageMagick.jl/issues/235
+# This can be removed once the `isbindingresolved` function is checked in InteractiveUtils.jl: subtypes 
+# So if it starts to cause problems in future version of Julia, it can be 
+# removed without any issues
+# This was copied from the Julia source code, and is used to avoid deprecation warnings
+# caused by deprecations on RGB1 and RGB4 in ColorTypes.jl
+function _subtypes_and_avoid_deprecation(x::Type)
+    mods = Base.loaded_modules_array()
+    xt = Base.unwrap_unionall(x)
+    if !isabstracttype(x) || !isa(xt, DataType)
+        # Fast path
+        return Type[]
+    end
+    sts = Vector{Any}()
+    while !isempty(mods)
+        m = pop!(mods)
+        xt = xt::DataType
+        for s in names(m, all = true)
+            if Base.isbindingresolved(m, s) && !Base.isdeprecated(m, s) && isdefined(m, s)
+                t = getfield(m, s)
+                dt = isa(t, UnionAll) ? Base.unwrap_unionall(t) : t
+                if isa(dt, DataType)
+                    if dt.name.name === s && dt.name.module == m && supertype(dt).name == xt.name
+                        ti = typeintersect(t, x)
+                        ti != Base.Bottom && push!(sts, ti)
+                    end
+                elseif isa(t, Module) && nameof(t) === s && parentmodule(t) === m && t !== m
+                    t === Base || push!(mods, t) # exclude Base, since it also parented by Main
+                end
+            end
+        end
+    end
+    return permute!(sts, sortperm(map(string, sts)))
+end
+for AC in vcat(_subtypes_and_avoid_deprecation(AlphaColor), _subtypes_and_avoid_deprecation(ColorAlpha))
     Cstr = ColorTypes.colorant_string(color_type(AC))
     if haskey(IMColordict, Cstr)
         IMColordict[ColorTypes.colorant_string(AC)] = IMColordict[Cstr]

test/runtests.jl

@@ -6,6 +6,7 @@ using Base.CoreLogging: SimpleLogger, with_logger
 include("constructed_images.jl")
 include("readremote.jl")
 include("badimages.jl")
+include("utilities.jl")
 
 workdir = joinpath(tempdir(), "Images")
 try

test/utilities.jl

@@ -0,0 +1,16 @@
+using InteractiveUtils: subtypes 
+@testset "Utilities" begin 
+  @testset "subtypes" begin 
+    println() 
+    println("---------------------------------------------------------------------------")
+    println("  This next test may cause deprecation warnings.")
+    println("  Remove this note if it stops doing that and remove the  function.")
+    println("    _subtypes_and_avoid_deprecation ")
+    println("  function from libmagickwand.jl.")
+    println("---------------------------------------------------------------------------")
+    println() 
+    @test subtypes(Integer) == ImageMagick._subtypes_and_avoid_deprecation(Integer) 
+    @test subtypes(ImageMagick.ColorAlpha) == ImageMagick._subtypes_and_avoid_deprecation(ImageMagick.ColorAlpha)
+    @test subtypes(ImageMagick.AlphaColor) == ImageMagick._subtypes_and_avoid_deprecation(ImageMagick.AlphaColor)
+  end 
+end