Handle measurement units

Due to JuliaPhysics/Measurements.jl#135

Author: ChrisRackauckas

Project.toml

@@ -32,6 +32,7 @@ Zygote = "0.6.56"
 julia = "1.6"
 
 [extensions]
+RecursiveArrayToolsMeasurementsExt = "Measurements"
 RecursiveArrayToolsTrackerExt = "Tracker"
 RecursiveArrayToolsZygoteExt = "Zygote"
 
@@ -40,6 +41,7 @@ Aqua = "4c88cf16-eb10-579e-8560-4a9242c79595"
 ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 LabelledArrays = "2ee39098-c373-598a-b85f-a56591580800"
 NLsolve = "2774e3e8-f4cf-5e23-947b-6d7e65073b56"
+Measurements = "eff96d63-e80a-5855-80a2-b1b0885c5ab7"
 OrdinaryDiffEq = "1dea7af3-3e70-54e6-95c3-0bf5283fa5ed"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Random = "9a3f8284-a2c9-5f02-9a11-845980a1fd5c"
@@ -52,8 +54,9 @@ Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["SafeTestsets", "Aqua", "ForwardDiff", "LabelledArrays", "NLsolve", "OrdinaryDiffEq", "Pkg", "Test", "Unitful", "Random", "StaticArrays", "StructArrays", "Zygote"]
+test = ["SafeTestsets", "Aqua", "ForwardDiff", "LabelledArrays", "NLsolve", "OrdinaryDiffEq", "Pkg", "Test", "Unitful", "Random", "StaticArrays", "StructArrays", "Zygote", "Measurements"]
 
 [weakdeps]
+Measurements = "eff96d63-e80a-5855-80a2-b1b0885c5ab7"
 Tracker = "9f7883ad-71c0-57eb-9f7f-b5c9e6d3789c"
 Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"

ext/RecursiveArrayToolsMeasurementsExt.jl

@@ -0,0 +1,14 @@
+module RecursiveArrayToolsMeasurementsExt
+
+import RecursiveArrayTools
+isdefined(Base, :get_extension) ? (import Measurements) : (import ..Measurements)
+
+function RecursiveArrayTools.recursive_unitless_bottom_eltype(a::Type{<:Measurements.Measurement})
+    typeof(oneunit(a))
+end
+
+function RecursiveArrayTools.recursive_unitless_eltype(a::Type{<:Measurements.Measurement})
+    typeof(oneunit(a))
+end
+
+end

src/RecursiveArrayTools.jl

@@ -31,6 +31,7 @@ Base.convert(T::Type{<:GPUArraysCore.AbstractGPUArray}, VA::AbstractVectorOfArra
 import Requires
 @static if !isdefined(Base, :get_extension)
     function __init__()
+        Requires.@require Measurements="eff96d63-e80a-5855-80a2-b1b0885c5ab7" begin include("../ext/RecursiveArrayToolsMeasurementsExt.jl") end
         Requires.@require Tracker="9f7883ad-71c0-57eb-9f7f-b5c9e6d3789c" begin include("../ext/RecursiveArrayToolsTrackerExt.jl") end
         Requires.@require Zygote="e88e6eb3-aa80-5325-afca-941959d7151f" begin include("../ext/RecursiveArrayToolsZygoteExt.jl") end
     end

test/measurements.jl

@@ -0,0 +1,5 @@
+using RecursiveArrayTools, Measurements, Test
+
+x = 1.0 ± 0.0
+@test recursive_unitless_bottom_eltype(x) isa Measurements.Measurement
+@test recursive_unitless_eltype(x) isa Measurements.Measurement

test/runtests.jl

@@ -33,6 +33,7 @@ end
         @time @safetestset "Linear Algebra Tests" begin include("linalg.jl") end
         @time @safetestset "Upstream Tests" begin include("upstream.jl") end
         @time @safetestset "Adjoint Tests" begin include("adjoints.jl") end
+        @time @safetestset "Measurement Tests" begin include("measurements.jl") end
     end
 
     if !is_APPVEYOR && GROUP == "Downstream"