Select by axis values doesn't preserve the order

[wytbella]

When selecting an AxisArray by index, it returns the correct order as expected. However, if one selects by axis values, it doesn’t preserve the order (see example below).

julia> tmp = AxisArray(rand(2,3), x=[:a, :b], y=[:A, :B, :C])
2-dimensional AxisArray{Float64,2,...} with axes:
    :x, [:a, :b]
    :y, [:A, :B, :C]
And data, a 2×3 Array{Float64,2}:
 0.373003  0.355006  0.158701
 0.691354  0.277119  0.651728
julia> tmp[[2,1],:]
2-dimensional AxisArray{Float64,2,...} with axes:
    :x, [:b, :a]
    :y, [:A, :B, :C]
And data, a 2×3 Array{Float64,2}:
 0.691354  0.277119  0.651728
 0.373003  0.355006  0.158701
julia> tmp[[:b, :a],:]
2-dimensional AxisArray{Float64,2,...} with axes:
    :x, [:a, :b]
    :y, [:A, :B, :C]
And data, a 2×3 Array{Float64,2}:
 0.373003  0.355006  0.158701
 0.691354  0.277119  0.651728

[mcabbott]

And worse if you repeat them:

julia> tmp[[2, 1, 1], :]
2-dimensional AxisArray{Float64,2,...} with axes:
    :x, [:b, :a, :a]
    :y, [:A, :B, :C]
And data, a 3×3 Array{Float64,2}:
 0.352127  0.787136  0.725084
 0.521467  0.939554  0.828499
 0.521467  0.939554  0.828499

julia> tmp[[:b, :a, :a], :]
ERROR: ArgumentError: index Symbol[] not found
Stacktrace:
 [1] axisindexes(::Type{AxisArrays.Categorical}, ::Array{Symbol,1}, ::Array{Symbol,1}) at /Users/me/.julia/packages/AxisArrays/IFpjG/src/indexing.jl:329