Add ReverseDiff weak dep

with backwards compatibility. Comes from SciMLSensitivity.jl back compat split.

Author: ChrisRackauckas

Project.toml

@@ -20,6 +20,12 @@ SymbolicIndexingInterface = "2efcf032-c050-4f8e-a9bb-153293bab1f5"
 Tables = "bd369af6-aec1-5ad0-b16a-f7cc5008161c"
 ZygoteRules = "700de1a5-db45-46bc-99cf-38207098b444"
 
+[weakdeps]
+ReverseDiff = "37e2e3b7-166d-5795-8a7a-e32c996b4267"
+
+[extensions]
+RecursiveArrayToolsReverseDiffExt = "ReverseDiff"
+
 [compat]
 Adapt = "3"
 ArrayInterfaceCore = "0.1.1"

ext/RecursiveArrayToolsReverseDiffExt.jl

@@ -0,0 +1,15 @@
+module RecursiveArrayToolsReverseDiffExt
+
+function RecursiveArrayTools.recursivecopy!(b::AbstractArray{T, N},
+                                            a::AbstractArray{T2, N}) where {
+                                                                            T <:
+                                                                            Tracker.TrackedArray,
+                                                                            T2 <:
+                                                                            Tracker.TrackedArray,
+                                                                            N}
+    @inbounds for i in eachindex(a)
+        b[i] = copy(a[i])
+    end
+end
+
+end

src/RecursiveArrayTools.jl

@@ -42,6 +42,13 @@ function ChainRulesCore.rrule(T::Type{<:GPUArraysCore.AbstractGPUArray},
     T(xs), ȳ -> (NoTangent(), ȳ)
 end
 
+import Requires
+function __init__()
+    @static if !isdefined(Base, :get_extension)
+        Requires.@require ReverseDiff="37e2e3b7-166d-5795-8a7a-e32c996b4267" begin include("../ext/RecursiveArrayToolsReverseDiffExt.jl") end
+    end
+end
+
 export VectorOfArray, DiffEqArray, AbstractVectorOfArray, AbstractDiffEqArray,
        AllObserved, vecarr_to_vectors, tuples