Make things kind-of type stable when chunksize is not specified

Author: avik-pal

src/highlevel/common.jl

@@ -186,7 +186,8 @@ function sparse_jacobian(ad::AbstractADType, sd::AbstractMaybeSparsityDetection,
         kwargs...)
     cache = sparse_jacobian_cache(ad, sd, args...; kwargs...)
     J = init_jacobian(cache)
-    return sparse_jacobian!(J, ad, cache, args...)
+    sparse_jacobian!(J, ad, cache, args...)
+    return J
 end
 
 """
@@ -199,7 +200,8 @@ Jacobian at every function call
 function sparse_jacobian(ad::AbstractADType, cache::AbstractMaybeSparseJacobianCache,
         args...)
     J = init_jacobian(cache)
-    return sparse_jacobian!(J, ad, cache, args...)
+    sparse_jacobian!(J, ad, cache, args...)
+    return J
 end
 
 """
@@ -216,7 +218,8 @@ with the same cache to compute the jacobian.
 function sparse_jacobian!(J::AbstractMatrix, ad::AbstractADType,
         sd::AbstractMaybeSparsityDetection, args...; kwargs...)
     cache = sparse_jacobian_cache(ad, sd, args...; kwargs...)
-    return sparse_jacobian!(J, ad, cache, args...)
+    sparse_jacobian!(J, ad, cache, args...)
+    return J
 end
 
 ## Internal

src/highlevel/finite_diff.jl

@@ -6,6 +6,8 @@ struct FiniteDiffJacobianCache{CO, CA, J, FX, X} <: AbstractMaybeSparseJacobianC
     x::X
 end
 
+__getfield(c::FiniteDiffJacobianCache, ::Val{:jac_prototype}) = c.jac_prototype
+
 function sparse_jacobian_cache(fd::Union{AutoSparseFiniteDiff, AutoFiniteDiff},
         sd::AbstractMaybeSparsityDetection, f::F, x; fx = nothing) where {F}
     coloring_result = sd(fd, f, x)

src/highlevel/forward_mode.jl

@@ -6,15 +6,20 @@ struct ForwardDiffJacobianCache{CO, CA, J, FX, X} <: AbstractMaybeSparseJacobian
     x::X
 end
 
+__getfield(c::ForwardDiffJacobianCache, ::Val{:jac_prototype}) = c.jac_prototype
+
 struct SparseDiffToolsTag end
 
+__standard_tag(::Nothing, x) = ForwardDiff.Tag(SparseDiffToolsTag(), eltype(x))
+__standard_tag(tag, _) = tag
+
 function sparse_jacobian_cache(ad::Union{AutoSparseForwardDiff, AutoForwardDiff},
         sd::AbstractMaybeSparsityDetection, f::F, x; fx = nothing) where {F}
     coloring_result = sd(ad, f, x)
     fx = fx === nothing ? similar(f(x)) : fx
     if coloring_result isa NoMatrixColoring
         cache = ForwardDiff.JacobianConfig(f, x, __chunksize(ad, x),
-            ifelse(ad.tag === nothing, SparseDiffToolsTag(), ad.tag))
+            __standard_tag(ad.tag, x))
         jac_prototype = nothing
     else
         cache = ForwardColorJacCache(f, x, __chunksize(ad); coloring_result.colorvec,
@@ -29,7 +34,7 @@ function sparse_jacobian_cache(ad::Union{AutoSparseForwardDiff, AutoForwardDiff}
     coloring_result = sd(ad, f!, fx, x)
     if coloring_result isa NoMatrixColoring
         cache = ForwardDiff.JacobianConfig(f!, fx, x, __chunksize(ad, x),
-            ifelse(ad.tag === nothing, SparseDiffToolsTag(), ad.tag))
+            __standard_tag(ad.tag, x))
         jac_prototype = nothing
     else
         cache = ForwardColorJacCache(f!, x, __chunksize(ad); coloring_result.colorvec,
@@ -44,7 +49,8 @@ function sparse_jacobian!(J::AbstractMatrix, _, cache::ForwardDiffJacobianCache,
     if cache.cache isa ForwardColorJacCache
         forwarddiff_color_jacobian(J, f, x, cache.cache) # Use Sparse ForwardDiff
     else
-        ForwardDiff.jacobian!(J, f, x, cache.cache) # Don't try to exploit sparsity
+        # Disable tag checking since we set the tag to our custom tag
+        ForwardDiff.jacobian!(J, f, x, cache.cache, Val(false)) # Don't try to exploit sparsity
     end
     return J
 end
@@ -54,7 +60,8 @@ function sparse_jacobian!(J::AbstractMatrix, _, cache::ForwardDiffJacobianCache,
     if cache.cache isa ForwardColorJacCache
         forwarddiff_color_jacobian!(J, f!, x, cache.cache) # Use Sparse ForwardDiff
     else
-        ForwardDiff.jacobian!(J, f!, fx, x, cache.cache) # Don't try to exploit sparsity
+        # Disable tag checking since we set the tag to our custom tag
+        ForwardDiff.jacobian!(J, f!, fx, x, cache.cache, Val(false)) # Don't try to exploit sparsity
     end
     return J
 end

src/highlevel/reverse_mode.jl

@@ -7,6 +7,8 @@ struct ReverseModeJacobianCache{CO, CA, J, FX, X, I} <: AbstractMaybeSparseJacob
     idx_vec::I
 end
 
+__getfield(c::ReverseModeJacobianCache, ::Val{:jac_prototype}) = c.jac_prototype
+
 function sparse_jacobian_cache(ad::Union{AutoEnzyme, AbstractReverseMode},
         sd::AbstractMaybeSparsityDetection, f::F, x; fx = nothing) where {F}
     fx = fx === nothing ? similar(f(x)) : fx