Fix dimension for empty wrapped quantity arrays

[MilesCranmerBot]

Fixes #224.

This updates the generic quantity-array dimension method so an empty array wrapper can inherit dimensions from a quantity-bearing parent, instead of falling through to first. Direct empty QuantityArray values keep using their stored dimensions.

Verification:

• /usr/local/bin/julia --project=. -e 'using Pkg; Pkg.test()' passed (10364 pass, 6 broken)
• Direct AxisKeys reproduction from dimension fetches fist item of AbstractArray even if empty #224 passes in a temporary environment

[github-actions]

Benchmark Results (Julia v1.10)

Time benchmarks

	main	8c4fde2...	main / 8c4fde2...
Quantity/creation/Quantity(x)	3.13 ± 0.01 ns	3.13 ± 0.01 ns	1 ± 0.0045
Quantity/creation/Quantity(x, length=y)	3.49 ± 0.01 ns	3.49 ± 0.01 ns	1 ± 0.0041
Quantity/with_numbers/*real	4.18 ± 0.01 ns	3.14 ± 0.01 ns	1.33 ± 0.0053
Quantity/with_numbers/^int	8.39 ± 2.4 ns	8.39 ± 2.4 ns	1 ± 0.41
Quantity/with_numbers/^int * real	8.39 ± 2.8 ns	8.39 ± 2.8 ns	1 ± 0.47
Quantity/with_quantity/+y	4.13 ± 0.08 ns	4.16 ± 0.08 ns	0.993 ± 0.027
Quantity/with_quantity//y	3.5 ± 0.01 ns	3.5 ± 0.01 ns	1 ± 0.004
Quantity/with_self/dimension	3.13 ± 0.01 ns	3.13 ± 0.01 ns	1 ± 0.0045
Quantity/with_self/inv	3.48 ± 0.01 ns	3.48 ± 0.01 ns	1 ± 0.0041
Quantity/with_self/ustrip	3.13 ± 0.001 ns	3.13 ± 0.001 ns	1 ± 0.00045
QuantityArray/broadcasting/multi_array_of_quantities	0.151 ± 0.01 ms	0.151 ± 0.011 ms	0.999 ± 0.1
QuantityArray/broadcasting/multi_normal_array	0.0597 ± 0.0034 ms	0.063 ± 0.0035 ms	0.948 ± 0.075
QuantityArray/broadcasting/multi_quantity_array	0.173 ± 0.0017 ms	0.173 ± 0.0023 ms	1 ± 0.017
QuantityArray/broadcasting/x^2_array_of_quantities	25.6 ± 1.9 μs	25.5 ± 2.1 μs	1.01 ± 0.11
QuantityArray/broadcasting/x^2_normal_array	3.9 ± 0.39 μs	3.93 ± 0.43 μs	0.993 ± 0.15
QuantityArray/broadcasting/x^2_quantity_array	8.24 ± 0.33 μs	8.25 ± 0.34 μs	0.999 ± 0.057
QuantityArray/broadcasting/x^4_array_of_quantities	0.0871 ± 0.0015 ms	0.0868 ± 0.0015 ms	1 ± 0.024
QuantityArray/broadcasting/x^4_normal_array	0.0531 ± 0.0035 ms	0.0561 ± 0.00023 ms	0.946 ± 0.062
QuantityArray/broadcasting/x^4_quantity_array	0.053 ± 0.0035 ms	0.0562 ± 0.0034 ms	0.942 ± 0.083
time_to_load	0.208 ± 0.00042 s	0.209 ± 0.0012 s	0.996 ± 0.0062

Memory benchmarks

	main	8c4fde2...	main / 8c4fde2...
Quantity/creation/Quantity(x)	0 allocs: 0 B	0 allocs: 0 B
Quantity/creation/Quantity(x, length=y)	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/*real	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/^int	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/^int * real	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_quantity/+y	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_quantity//y	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/dimension	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/inv	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/ustrip	0 allocs: 0 B	0 allocs: 0 B
QuantityArray/broadcasting/multi_array_of_quantities	2 allocs: 0.382 MB	2 allocs: 0.382 MB	1
QuantityArray/broadcasting/multi_normal_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
QuantityArray/broadcasting/multi_quantity_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
QuantityArray/broadcasting/x^2_array_of_quantities	2 allocs: 0.382 MB	2 allocs: 0.382 MB	1
QuantityArray/broadcasting/x^2_normal_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
QuantityArray/broadcasting/x^2_quantity_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
QuantityArray/broadcasting/x^4_array_of_quantities	2 allocs: 0.382 MB	2 allocs: 0.382 MB	1
QuantityArray/broadcasting/x^4_normal_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
QuantityArray/broadcasting/x^4_quantity_array	2 allocs: 0.0763 MB	2 allocs: 0.0763 MB	1
time_to_load	0.153 k allocs: 14.5 kB	0.153 k allocs: 14.5 kB	1

[github-actions]

Benchmark Results (Julia v1)

Time benchmarks

	main	8c4fde2...	main / 8c4fde2...
Quantity/creation/Quantity(x)	3.41 ± 0.01 ns	3.1 ± 0.01 ns	1.1 ± 0.0048
Quantity/creation/Quantity(x, length=y)	3.41 ± 0.01 ns	3.41 ± 0.01 ns	1 ± 0.0042
Quantity/with_numbers/*real	3.1 ± 0.01 ns	3.41 ± 0.01 ns	0.909 ± 0.004
Quantity/with_numbers/^int	12.1 ± 1 ns	12.1 ± 0.98 ns	1 ± 0.12
Quantity/with_numbers/^int * real	11.9 ± 0.99 ns	11.8 ± 0.95 ns	1.01 ± 0.12
Quantity/with_quantity/+y	4.04 ± 0.001 ns	4.04 ± 0.001 ns	1 ± 0.00035
Quantity/with_quantity//y	3.41 ± 0.01 ns	3.1 ± 0.01 ns	1.1 ± 0.0048
Quantity/with_self/dimension	2.79 ± 0.01 ns	3.1 ± 0.01 ns	0.9 ± 0.0043
Quantity/with_self/inv	3.11 ± 0.01 ns	3.41 ± 0.01 ns	0.912 ± 0.004
Quantity/with_self/ustrip	2.79 ± 0.01 ns	2.79 ± 0.01 ns	1 ± 0.0051
QuantityArray/broadcasting/multi_array_of_quantities	0.11 ± 0.0055 ms	0.113 ± 0.0065 ms	0.974 ± 0.075
QuantityArray/broadcasting/multi_normal_array	0.0471 ± 0.00023 ms	0.0471 ± 0.00023 ms	1 ± 0.0069
QuantityArray/broadcasting/multi_quantity_array	0.0501 ± 0.00058 ms	0.0501 ± 0.00042 ms	1 ± 0.014
QuantityArray/broadcasting/x^2_array_of_quantities	27.1 ± 11 μs	27.4 ± 10 μs	0.986 ± 0.54
QuantityArray/broadcasting/x^2_normal_array	2.58 ± 3.2 μs	2.77 ± 4.5 μs	0.928 ± 1.9
QuantityArray/broadcasting/x^2_quantity_array	6.56 ± 0.28 μs	4.45 ± 2 μs	1.48 ± 0.65
QuantityArray/broadcasting/x^4_array_of_quantities	0.0821 ± 0.0075 ms	0.0819 ± 0.005 ms	1 ± 0.11
QuantityArray/broadcasting/x^4_normal_array	0.0436 ± 0.00018 ms	0.0436 ± 0.00018 ms	0.999 ± 0.0059
QuantityArray/broadcasting/x^4_quantity_array	0.0437 ± 0.0002 ms	0.0468 ± 0.00025 ms	0.934 ± 0.0066
time_to_load	0.193 ± 0.0083 s	0.2 ± 0.0033 s	0.967 ± 0.044

Memory benchmarks

	main	8c4fde2...	main / 8c4fde2...
Quantity/creation/Quantity(x)	0 allocs: 0 B	0 allocs: 0 B
Quantity/creation/Quantity(x, length=y)	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/*real	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/^int	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_numbers/^int * real	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_quantity/+y	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_quantity//y	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/dimension	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/inv	0 allocs: 0 B	0 allocs: 0 B
Quantity/with_self/ustrip	0 allocs: 0 B	0 allocs: 0 B
QuantityArray/broadcasting/multi_array_of_quantities	3 allocs: 0.382 MB	3 allocs: 0.382 MB	1
QuantityArray/broadcasting/multi_normal_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
QuantityArray/broadcasting/multi_quantity_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
QuantityArray/broadcasting/x^2_array_of_quantities	3 allocs: 0.382 MB	3 allocs: 0.382 MB	1
QuantityArray/broadcasting/x^2_normal_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
QuantityArray/broadcasting/x^2_quantity_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
QuantityArray/broadcasting/x^4_array_of_quantities	3 allocs: 0.382 MB	3 allocs: 0.382 MB	1
QuantityArray/broadcasting/x^4_normal_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
QuantityArray/broadcasting/x^4_quantity_array	3 allocs: 0.0764 MB	3 allocs: 0.0764 MB	1
time_to_load	0.145 k allocs: 11 kB	0.145 k allocs: 11 kB	1

[codecov]

Codecov Report

✅ All modified and coverable lines are covered by tests.
✅ Project coverage is 99.17%. Comparing base (8f18f23) to head (8c4fde2).
⚠️ Report is 3 commits behind head on main.

Additional details and impacted files

@@           Coverage Diff           @@
##             main     #226   +/-   ##
=======================================
  Coverage   99.16%   99.17%           
=======================================
  Files          23       23           
  Lines        1320     1330   +10     
=======================================
+ Hits         1309     1319   +10     
  Misses         11       11           

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[MilesCranmer]

@MilesCranmerBot please address comments above

[MilesCranmerBot]

Addressed in MilesCranmerBot/DynamicQuantities.jl@e4ec781.

• Removed the unreachable applicable(parent, aq) guard.
• Added coverage for _parent_dimension(Quantity[]) === nothing.
• Ran: JULIA_LOAD_PATH="$PWD/test:$PWD:@stdlib" /usr/local/bin/julia --project=test test/unittests.jl