use nonlinear func if present

Author: oscardssmith

Diff for: lib/OrdinaryDiffEqNonlinearSolve/src/utils.jl

@@ -206,19 +206,24 @@ function build_nlsolver(
         if nlalg isa NonlinearSolveAlg
             α = tTypeNoUnits(α)
             dt = tTypeNoUnits(dt)
-            if isdae
-                nlf = (ztmp, z, p) -> begin
-                    tmp, ustep, γ, α, tstep, k, invγdt, _p, dt, f = p
-                    _compute_rhs!(tmp, ztmp, ustep, γ, α, tstep, k, invγdt, _p, dt, f, z)[1]
+            if isnothing(f.nlfunc)
+                if isdae
+                    nlf = (ztmp, z, p) -> begin
+                        tmp, ustep, γ, α, tstep, k, invγdt, _p, dt, f = p
+                        _compute_rhs!(tmp, ztmp, ustep, γ, α, tstep, k, invγdt, _p, dt, f, z)[1]
+                    end
+                    nlp_params = (tmp, ustep, γ, α, tstep, k, invγdt, p, dt, f)
+                else
+                    nlf = (ztmp, z, p) -> begin
+                        tmp, ustep, γ, α, tstep, k, invγdt, method, _p, dt, f = p
+                        _compute_rhs!(
+                            tmp, ztmp, ustep, γ, α, tstep, k, invγdt, method, _p, dt, f, z)[1]
+                    end
+                    nlp_params = (tmp, ustep, γ, α, tstep, k, invγdt, DIRK, p, dt, f)
                 end
-                nlp_params = (tmp, ustep, γ, α, tstep, k, invγdt, p, dt, f)
             else
-                nlf = (ztmp, z, p) -> begin
-                    tmp, ustep, γ, α, tstep, k, invγdt, method, _p, dt, f = p
-                    _compute_rhs!(
-                        tmp, ztmp, ustep, γ, α, tstep, k, invγdt, method, _p, dt, f, z)[1]
-                end
-                nlp_params = (tmp, ustep, γ, α, tstep, k, invγdt, DIRK, p, dt, f)
+                nlf = f.nlfunc
+                nlp_params =()
             end
             prob = NonlinearProblem(NonlinearFunction(nlf), ztmp, nlp_params)
             cache = init(prob, nlalg.alg)