Split AD tests into a dedicated off-downgrade group (Mooncake 0.5 needs >= 1.10.8) (#617)

* Run downgrade CI on Julia 1.11 (Mooncake 0.5 needs >= 1.10.8)

The Downgrade (Core) job fails on master with `ERROR: LoadError:
Unsatisfiable`. The downgrade resolver runs `--min=@deps` and minimizes
the Julia version to the floor implied by the workflow's Julia channel.
With the default `lts` channel that floor is 1.10.0, but every Mooncake
0.5.x release (used by RecursiveArrayToolsMooncakeExt) declares
`julia = "1.10.8 - 1.10, 1.11.6 - 1"`, so no Mooncake version is
installable at 1.10.0 and Mooncake gets no candidate version.

Reproduced locally with the actual julia-actions/julia-downgrade-compat
downgrade.jl driver against a checkout of this repo:
  julia_version=1.10 -> ERROR: LoadError: Unsatisfiable
  julia_version=1.11 -> "Successfully resolved minimal versions"

Pin the downgrade job to Julia 1.11 (the same approach OrdinaryDiffEq.jl
uses), where 1.10.8+ is satisfied and every declared floor is jointly
installable. Core support for Julia 1.10 is unchanged and is still
exercised by the normal lts test legs; this only affects which Julia the
downgrade resolver minimizes against.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Fix typo: tupe -> type in named_array_partition comment

Fixes the Spell Check with Typos CI failure flagging `tupe` in
src/named_array_partition.jl.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

* Split AD tests into a dedicated off-downgrade group

Move the Mooncake/Zygote/ForwardDiff/ReverseDiff test files out of the root
Core group and into a dedicated `AD` group with its own sub-environment
(test/AD/Project.toml, [sources] RecursiveArrayTools = path), modeled on the
NoPre group. The AD group is marked in_all = false and is not run in the
Downgrade lane (which runs only Core), so its deps are never fed to the
downgrade resolver.

This removes Mooncake (and the other AD backends) from the root [targets].test
set. The downgrade workflow builds/tests with project: "@." (the repo root) and
minimizes every direct dep plus the Julia version to the 1.10.0 LTS floor;
Mooncake 0.5 requires Julia >= 1.10.8, so at the 1.10.0 floor it was
Unsatisfiable. With Mooncake out of the root test target the resolver no longer
sees it, fixing the wall at the source instead of pinning the downgrade Julia
version.

This reverts the Downgrade.yml julia-version: "1.11" approach from this branch
in favor of the AD split. Mooncake/Zygote/ForwardDiff/ReverseDiff remain as
[weakdeps]+[compat] for the AD extensions; the AD tests still run (in their own
group on a normal Julia). The tupe->type spellcheck fix is kept.

Co-Authored-By: Chris Rackauckas <accounts@chrisrackauckas.com>
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

---------

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: 3 people

Project.toml

@@ -85,10 +85,8 @@ julia = "1.10"
 
 [extras]
 FastBroadcast = "7034ab61-46d4-4ed7-9d0f-46aef9175898"
-ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
 KernelAbstractions = "63c18a36-062a-441e-b654-da1e3ab1ce7c"
 Measurements = "eff96d63-e80a-5855-80a2-b1b0885c5ab7"
-Mooncake = "da2b9cff-9c12-43a0-ae48-6db2b0edb7d6"
 MonteCarloMeasurements = "0987c9cc-fe09-11e8-30f0-b96dd679fdca"
 Pkg = "44cfe95a-1eb2-52ea-b672-e2afdf69b78f"
 Polyester = "f517fe37-dbe3-4b94-8317-1923a5111588"
@@ -101,9 +99,7 @@ StaticArrays = "90137ffa-7385-5640-81b9-e52037218182"
 Statistics = "10745b16-79ce-11e8-11f9-7d13ad32a3b2"
 StructArrays = "09ab397b-f2b6-538f-b94a-2f83cf4a842a"
 Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
-Tracker = "9f7883ad-71c0-57eb-9f7f-b5c9e6d3789c"
 Unitful = "1986cc42-f94f-5a68-af5c-568840ba703d"
-Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
 
 [targets]
-test = ["FastBroadcast", "ForwardDiff", "KernelAbstractions", "Measurements", "Mooncake", "Pkg", "Polyester", "Random", "RecursiveArrayToolsShorthandConstructors", "ReverseDiff", "SafeTestsets", "SciMLTesting", "SparseArrays", "StaticArrays", "Statistics", "StructArrays", "Tables", "Test", "Unitful", "Zygote"]
+test = ["FastBroadcast", "KernelAbstractions", "Measurements", "Pkg", "Polyester", "Random", "RecursiveArrayToolsShorthandConstructors", "SafeTestsets", "SciMLTesting", "SparseArrays", "StaticArrays", "Statistics", "StructArrays", "Tables", "Test", "Unitful"]

src/named_array_partition.jl

@@ -146,7 +146,7 @@ function Base.similar(
     return NamedArrayPartition(similar(ArrayPartition(x)), getfield(x, :names_to_indices))
 end
 
-# when broadcasting with ArrayPartition + another array type, the output is the other array tupe
+# when broadcasting with ArrayPartition + another array type, the output is the other array type
 function Base.BroadcastStyle(
         ::Broadcast.ArrayStyle{NamedArrayPartition}, ::Broadcast.DefaultArrayStyle{1}
     )

test/AD/Project.toml

@@ -0,0 +1,18 @@
+[deps]
+ForwardDiff = "f6369f11-7733-5829-9624-2563aa707210"
+Mooncake = "da2b9cff-9c12-43a0-ae48-6db2b0edb7d6"
+RecursiveArrayTools = "731186ca-8d62-57ce-b412-fbd966d074cd"
+ReverseDiff = "37e2e3b7-166d-5795-8a7a-e32c996b4267"
+Test = "8dfed614-e22c-5e08-85e1-65c5234f0b40"
+Zygote = "e88e6eb3-aa80-5325-afca-941959d7151f"
+
+[sources]
+RecursiveArrayTools = {path = "../.."}
+
+[compat]
+ForwardDiff = "0.10.38, 1"
+Mooncake = "0.5"
+RecursiveArrayTools = "4"
+ReverseDiff = "1.15"
+Test = "1"
+Zygote = "0.7"

test/Core/adjoints.jl test/AD/adjoints.jltest/Core/adjoints.jl renamed to test/AD/adjoints.jl

@@ -22,8 +22,6 @@ run_tests(;
         @time @safetestset "Table traits" include("Core/tabletraits.jl")
         @time @safetestset "StaticArrays Tests" include("Core/copy_static_array_test.jl")
         @time @safetestset "Linear Algebra Tests" include("Core/linalg.jl")
-        @time @safetestset "Adjoint Tests" include("Core/adjoints.jl")
-        @time @safetestset "Mooncake Tests" include("Core/mooncake.jl")
         return @time @safetestset "Measurement Tests" include("Core/measurements.jl")
     end,
     groups = Dict(
@@ -70,6 +68,18 @@ run_tests(;
                 return @time @safetestset "JET Tests" include("NoPre/jet_tests.jl")
             end,
         ),
+        # AD lives in its own env (test/AD/Project.toml) so its heavy AD-backend
+        # deps (Mooncake/Zygote/ForwardDiff/ReverseDiff) stay out of the root test
+        # target. It is deliberately absent from `all` and not run in the Downgrade
+        # lane: Mooncake 0.5 requires Julia >= 1.10.8, which the downgrade resolver
+        # cannot satisfy when it minimizes Julia to the 1.10.0 LTS floor.
+        "AD" => (;
+            env = joinpath(@__DIR__, "AD"),
+            body = function ()
+                @time @safetestset "Adjoint Tests" include("AD/adjoints.jl")
+                return @time @safetestset "Mooncake Tests" include("AD/mooncake.jl")
+            end,
+        ),
     ),
     qa = (;
         env = joinpath(@__DIR__, "QA"),

test/Core/mooncake.jl test/AD/mooncake.jltest/Core/mooncake.jl renamed to test/AD/mooncake.jl

@@ -18,6 +18,16 @@ num_threads = 2
 versions = ["lts", "1"]
 num_threads = 2
 
+# AD backends (Mooncake/Zygote/ForwardDiff/ReverseDiff) live in their own env
+# (test/AD/Project.toml) and run as their own CI group. in_all = false keeps them
+# out of the "All" aggregate, and the Downgrade lane only runs "Core", so AD is
+# never fed to the downgrade resolver -- Mooncake 0.5 needs Julia >= 1.10.8, which
+# the downgrade resolver cannot place when it minimizes Julia to the 1.10.0 floor.
+[AD]
+versions = ["lts", "1"]
+num_threads = 2
+in_all = false
+
 [GPU]
 versions = ["1"]
 runner = ["self-hosted", "Linux", "X64", "gpu"]