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dimension fetches fist item of AbstractArray even if empty #224
Description
While wrapping QuantityArrays with KeyedArray from AxisKeys.jl, I met an edge case of dimension with empty arrays.
] activate --temp
] add AxisKeys
] add DynamicQuantities
A = KeyedArray(QuantityArray(Matrix{Float64}(undef,0,6),us"s"); time = Float64[], channel = ["$i" for i in 1:6])
dimension(A)This throws
julia> dimension(A)
ERROR: BoundsError: attempt to access 0×6 NamedDimsArray(QuantityArray(::Matrix{Float64}, ::Quantity{Float64, SymbolicDimensions{FRInt32}}), (:time, :channel)) at index [1]
Stacktrace:
[1] throw_boundserror(A::NamedDimsArray{(:time, :channel), Quantity{…}, 2, QuantityArray{…}}, I::Tuple{Int64})
@ Base .\essentials.jl:15
[2] checkbounds
@ .\abstractarray.jl:699 [inlined]
[3] getindex
@ D:\bamboo\.julia\packages\AxisKeys\a6h2b\src\struct.jl:76 [inlined]
[4] first
@ .\abstractarray.jl:452 [inlined]
[5] dimension(aq::KeyedArray{Quantity{…}, 2, NamedDimsArray{…}, Tuple{…}})
@ DynamicQuantities D:\bamboo\.julia\packages\DynamicQuantities\wqpWc\src\utils.jl:442
[6] top-level scope
@ REPL[26]:1
Some type information was truncated. Use `show(err)` to see complete types.
at
DynamicQuantities.jl/src/utils.jl
Line 442 in f619e16
I am not sure how this should be circumvented. If the array is empty, it is obvious that all elements should be of the same type. It may require an additional dispatch.
Activity
MilesCranmer commentedon Jun 8, 2026
Thanks! Yeah, I guess that
dimension(::QuantityArray)should definitely work, even when the array is empty. I am surprised it is getting forwarded to theAbstractArraycall... strange. @MilesCranmerBot can you please make a PR fixing this?I am not sure how to handle the case of an empty
AbstractArray. Maybe just promote the quantity type and return a dimensionless 1.0? But maybe that is a second issue.MilesCranmerBot commentedon Jun 8, 2026
Opened PR: #226
Commit: 372fae1
Verified locally:
QuantityArray/parent-wrapper check passedPkg.test(; test_args=["Assorted unittests"])passed (10364 pass, 6 broken)Current PR checks are partly green with Julia 1 and docs still pending.