Restore DelayDiffEq extension hooks as public API (#4073)

Co-authored-by: ChrisRackauckas-Claude <accounts@chrisrackauckas.com>

Author: ChrisRackauckas-Claude

docs/src/devtools/internals/public_api.md

@@ -10,9 +10,9 @@ documented under the API section.
     Do not build application code against these hooks. They exist so solver
     packages can extend common traits, controllers, interpolation hooks, and
     initialization protocols without depending on undocumented implementation
-    details. Concrete per-algorithm cache types and low-level nonlinear solve
-    helper functions are not public API; only the abstract cache supertypes a
-    solver package subtypes are.
+    details. Concrete per-algorithm caches and low-level nonlinear-solve helpers
+    remain internal unless listed below; the listed automatic-switch caches and
+    nonlinear-solver hooks are shared with sibling integrator packages.
 
 ## DiffEqBase solver hooks
 
@@ -99,6 +99,7 @@ OrdinaryDiffEqCore.StochasticDiffEqJumpNewtonDiffusionAdaptiveAlgorithm
 
 ```@docs
 OrdinaryDiffEqCore.CompositeAlgorithm
+OrdinaryDiffEqCore.AutoSwitchCache
 OrdinaryDiffEqCore.isautoswitch
 OrdinaryDiffEqCore.default_autoswitch
 OrdinaryDiffEqCore.unwrap_alg
@@ -193,6 +194,7 @@ extension points.
 ```@docs
 OrdinaryDiffEqCore.AbstractNLSolver
 OrdinaryDiffEqCore.AbstractNLSolverAlgorithm
+OrdinaryDiffEqCore.AbstractNLSolverCache
 OrdinaryDiffEqCore.nlsolve_f
 OrdinaryDiffEqCore.get_W
 OrdinaryDiffEqCore.set_new_W!
@@ -204,6 +206,12 @@ OrdinaryDiffEqCore.isJcurrent
 OrdinaryDiffEqCore.resize_J_W!
 OrdinaryDiffEqCore.resize_nlsolver!
 OrdinaryDiffEqCore.default_nlsolve
+OrdinaryDiffEqNonlinearSolve.nlsolve!
+OrdinaryDiffEqNonlinearSolve.nlsolvefail
+OrdinaryDiffEqNonlinearSolve.compute_step!
+OrdinaryDiffEqNonlinearSolve.initial_η
+OrdinaryDiffEqNonlinearSolve.anderson
+OrdinaryDiffEqNonlinearSolve.anderson!
 ```
 
 ## Jacobian / W-matrix / differentiation configuration
@@ -249,6 +257,7 @@ OrdinaryDiffEqCore.OrdinaryDiffEqMutableCache
 OrdinaryDiffEqCore.StochasticDiffEqCache
 OrdinaryDiffEqCore.StochasticDiffEqConstantCache
 OrdinaryDiffEqCore.StochasticDiffEqMutableCache
+OrdinaryDiffEqCore.DefaultCache
 OrdinaryDiffEqCore.@cache
 OrdinaryDiffEqCore.alg_cache
 OrdinaryDiffEqCore.get_fsalfirstlast
@@ -266,6 +275,9 @@ OrdinaryDiffEqCore._ode_init
 OrdinaryDiffEqCore._initialize_dae!
 OrdinaryDiffEqCore.find_algebraic_vars_eqs
 OrdinaryDiffEqCore.get_differential_vars
+OrdinaryDiffEqCore.handle_callback_modifiers!
+OrdinaryDiffEqCore.resolve_stage_step_limiters
+OrdinaryDiffEqCore.trivial_limiter!
 ```
 
 ## Dense output / interpolation

lib/OrdinaryDiffEqCore/src/OrdinaryDiffEqCore.jl

@@ -429,12 +429,12 @@ include("precompilation_setup.jl")
     eval(
         Expr(
             :public,
-            :AbstractController, :AbstractControllerCache, :AbstractNLSolver, :AbstractNLSolverAlgorithm, :AbstractThreadingOption,
+            :AbstractController, :AbstractControllerCache, :AbstractNLSolver, :AbstractNLSolverAlgorithm, :AbstractNLSolverCache, :AbstractThreadingOption,
             :accept_step_controller, :alg_adaptive_order, :alg_autodiff, :alg_cache, :alg_difftype, :alg_extrapolates,
-            :alg_maximum_order, :alg_stability_size, :AutoAlgSwitch, :AutoSwitch, :BaseThreads,
+            :alg_maximum_order, :alg_stability_size, :AutoAlgSwitch, :AutoSwitch, :AutoSwitchCache, :BaseThreads,
             :beta1_default, :beta2_default, Symbol("@cache"), :COEFFICIENT_MULTISTEP, :CommonControllerOptions, :CompositeAlgorithm,
             :CompositeController, :constvalue, :Convergence, :current_extrapolant,
-            :current_interpolant, :DAEAlgorithm, :default_autoswitch, :default_controller, :default_linear_interpolation,
+            :current_interpolant, :DAEAlgorithm, :default_autoswitch, :DefaultCache, :default_controller, :default_linear_interpolation,
             :default_nlsolve, :DEOptions, :DIRK, :Divergence, :dt_required, :DummyController,
             :explicit_rk_docstring, :ExponentialAlgorithm, :FastConvergence, :gamma_default, :generic_solver_docstring,
             :get_current_adaptive_order, :get_current_alg_autodiff, :get_differential_vars, :get_EEst, :get_failfactor, :get_fsalfirstlast,
@@ -477,7 +477,7 @@ include("precompilation_setup.jl")
             # Integrator step / cache / initialization hooks.
             :_ode_init, :_determine_initdt, :ode_determine_initdt, :_initialize_dae!,
             :find_algebraic_vars_eqs, :postamble!, :apply_step!, :last_step_failed, :reset_alg_dependent_opts!,
-            :resolve_basic,
+            :handle_callback_modifiers!, :resolve_basic, :resolve_stage_step_limiters,
             # Noise hooks used by the SDE/RODE solver sublibs.
             :accept_noise!, :reinit_noise!, :reject_noise!, :save_noise!, :noise_curt,
             :is_noise_saveable,
@@ -487,7 +487,7 @@ include("precompilation_setup.jl")
             # OrdinaryDiffEqCache trio: every StochasticDiffEq solver cache subtypes one
             # of these, so they are a required solver-author extension point.
             :StochasticDiffEqCache, :StochasticDiffEqConstantCache,
-            :StochasticDiffEqMutableCache,
+            :StochasticDiffEqMutableCache, :trivial_limiter!,
         )
     )
 end

lib/OrdinaryDiffEqCore/src/algorithms.jl

@@ -334,6 +334,11 @@ end
 
 ################################################################################
 
+"""
+    trivial_limiter!(u, integrator, p, t)
+
+No-op stage/step limiter used when no solve-level limiter is supplied.
+"""
 @inline trivial_limiter!(u, integrator, p, t) = nothing
 
 ################################################################################

lib/OrdinaryDiffEqCore/test/qa/qa.jl

@@ -5,7 +5,13 @@ using SciMLTesting, OrdinaryDiffEqCore, Test
 const UNANALYZABLE = (OrdinaryDiffEqCore.Predictor,)
 
 @static if VERSION >= v"1.11.0-DEV.469"
-    @test Base.ispublic(OrdinaryDiffEqCore, :isdiscretecache)
+    for name in (
+            :AbstractNLSolverCache, :AutoSwitchCache, :DefaultCache,
+            :handle_callback_modifiers!, :isdiscretecache,
+            :resolve_stage_step_limiters, :trivial_limiter!,
+        )
+        @test Base.ispublic(OrdinaryDiffEqCore, name)
+    end
 end
 
 run_qa(

lib/OrdinaryDiffEqDefault/test/qa/qa.jl

@@ -50,10 +50,6 @@ without_local_project_sources(OrdinaryDiffEqDefault) do
                 # stale because of the unanalyzable enum submodule above.
                 ignore = (:Tsit5, :Vern7, :Rosenbrock23, :Rodas5P, :FBDF),
             ),
-            all_explicit_imports_are_public = (;
-                # Internal monorepo extension point; `AutoSwitchCache` is not user API.
-                ignore = (:AutoSwitchCache,),
-            ),
             all_qualified_accesses_are_public = (;
                 # `lorenz`/`lorenz_oop` are OrdinaryDiffEqCore precompile-workload
                 # test problems (defined in `precompilation_setup.jl`), deliberately

lib/OrdinaryDiffEqNonlinearSolve/src/OrdinaryDiffEqNonlinearSolve.jl

@@ -73,15 +73,16 @@ include("initialize_dae.jl")
 
 export BrownFullBasicInit, ShampineCollocationInit
 
-# Nonlinear-solver algorithms accepted by OrdinaryDiffEq implicit methods. The
-# lower-level build/step/Anderson helpers are implementation details, not public API.
+# Nonlinear-solver algorithms accepted by OrdinaryDiffEq implicit methods and the
+# solver-author hooks extended by sibling integrator packages.
 # The `public` keyword is only parseable on Julia >= 1.11.0-DEV.469, so it is
 # gated to keep the 1.10 floor parsing.
 @static if VERSION >= v"1.11.0-DEV.469"
     eval(
         Expr(
             :public,
-            :NLNewton, :NLFunctional, :NLAnderson, :HomotopyNonlinearSolveAlg
+            :NLNewton, :NLFunctional, :NLAnderson, :HomotopyNonlinearSolveAlg,
+            :nlsolve!, :nlsolvefail, :compute_step!, :initial_η, :anderson, :anderson!
         )
     )
 end

lib/OrdinaryDiffEqNonlinearSolve/test/qa/qa.jl

@@ -1,6 +1,12 @@
 using SciMLTesting, OrdinaryDiffEqNonlinearSolve, Test
 using Aqua
 
+@static if VERSION >= v"1.11.0-DEV.469"
+    for name in (:anderson, :anderson!, :compute_step!, :initial_η, :nlsolve!, :nlsolvefail)
+        @test Base.ispublic(OrdinaryDiffEqNonlinearSolve, name)
+    end
+end
+
 # Ambiguities are checked below over this package's own methods instead of Aqua's default
 # `[pkg, Base, Core]` module set; see the `Aqua.test_ambiguities` call.
 run_qa(
@@ -45,9 +51,6 @@ run_qa(
                 :AbstractSciMLOperator,
                 # OrdinaryDiffEqDifferentiation W-operator types (attributed to SciMLOperators).
                 :WOperator, :StaticWOperator,
-                # Owner-internal cross-sublibrary hooks with no public wrapper.
-                # OrdinaryDiffEqCore:
-                :AbstractNLSolverCache,
                 # OrdinaryDiffEqDifferentiation:
                 :build_J_W, :build_jac_config, :build_uf, :dolinsolve,
                 :is_always_new, :jacobian!, :jacobian2W!, :resize_jac_config!,