Indexing order is not preserved when indexing by name

[LilithHafner]

This seems pretty bad to me and I don't think it's documented. I'd like to call it a bug and fix it in minor release if that is acceptable.

julia> x = AxisArray([1,2], [:a, :b])
1-dimensional AxisArray{Int64,1,...} with axes:
    :row, [:a, :b]
And data, a 2-element Vector{Int64}:
 1
 2

julia> x[[:a, :b]] # Okay
1-dimensional AxisArray{Int64,1,...} with axes:
    :row, [:a, :b]
And data, a 2-element Vector{Int64}:
 1
 2

julia> x[[:b, :a]] # Should flip, but doesn't
1-dimensional AxisArray{Int64,1,...} with axes:
    :row, [:a, :b]
And data, a 2-element Vector{Int64}:
 1
 2

julia> x[[2, 1]] # Should flip and does
1-dimensional AxisArray{Int64,1,...} with axes:
    :row, [:b, :a]
And data, a 2-element Vector{Int64}:
 2
 1

Possibly related to #204

[LilithHafner]

Bump; I would be more than happy to submit a PR if it would be welcome.

[niclasmattsson]

This is an incredibly nasty bug, and fixing it should be top priority. Indexing by name is kind of the whole point of AxisArrays, and this bug silently produces incorrect results when you do. I'm surprised that this issue is three years old with no traffic.

I understand that the original developers have largely moved on and AxisArrays.jl isn't being actively maintained. But it is being used in production across the Julia ecosystem. @LilithHafner do you know if there is someone we can ping about this?

[timholy]

I'll try to review a PR if someone submits one. Feel free to ping me on slack if you don't get a response within a week or so.