`NonlinearFunction(::ODEFunction)` drops the vector argument of `jvp`/`vjp`, so `NonlinearProblem(::SteadyStateProblem)` throws for any ODE function with a `jvp`

Read the conversion wrappers in src/scimlfunctions.jl, especially NonlinearFunction{iip}(f::ODEFunction) and ODEFunction{iip}(f::NonlinearFunction), then check test/convert_tests.jl for existing conversion coverage. Add tests for jvp and vjp in both directions and for in-place and out-of-place functions. Done means the converted products match the originals at t = Inf and the conversions succeed.

When an ODEFunction is converted to a NonlinearFunction at t = Inf, the jvp and vjp wrappers copy the jac wrapper and lose the vector argument v. The resulting jvp has one argument too few, and the NonlinearFunction constructor rejects it. So NonlinearProblem(SteadyStateProblem(prob)) throws whenever prob.f has a jvp, both in place and out of place. The reverse conversion ODEFunction(::NonlinearFunction) has the same defect.

Versions

SciMLBase 3.58.0 (the latest registered release), Julia 1.12.6, Linux x86_64. The wrappers are unchanged on master (f75f097e, 2026-11-02, version 3.59.1). We read the source there but did not run it.

Reproducer

using SciMLBase

f!(du, u, p, t) = (du .= -u; nothing)
jvp!(Jv, v, u, p, t) = (Jv .= -v; nothing)            # documented in-place form
prob = SteadyStateProblem(ODEFunction{true}(f!; jvp = jvp!), [1.0, 2.0])

NonlinearProblem(prob)
# ERROR: Nonconforming functions detected. … Nonconforming functions: ["jvp"]

# out of place: jvp(v, u, p, t)
NonlinearFunction(ODEFunction{false}((u, p, t) -> -u; jvp = (v, u, p, t) -> -v))
# ERROR: All methods for the model function `f` had too few arguments. … Offending function: jvp
#   (::SciMLBase.var"#101#102")(u, p) @ scimlfunctions.jl:3409

# the reverse direction
ODEFunction(NonlinearFunction{true}((du, u, p) -> (du .= -u; nothing); jvp = (Jv, v, u, p) -> (Jv .= -v; nothing)))
# ERROR: Nonconforming functions detected. … Nonconforming functions: ["jvp"]

All three errors were reproduced on 3.58.0. NonlinearFunction(odef) called directly fails like the first case.

Actual vs expected

Actual: the conversions throw. If the arity check were skipped, the wrapper would call f.jvp(Jv, u, p, Inf), which is 4 arguments for a 5-argument function.

Expected: the conversion succeeds, and the converted jvp(Jv, v, u, p) equals f.jvp(Jv, v, u, p, Inf). Written by hand, this works:

nf = NonlinearFunction{true}((du, u, p) -> f!(du, u, p, Inf); jvp = (Jv, v, u, p) -> jvp!(Jv, v, u, p, Inf))
Jv = zeros(2); nf.jvp(Jv, [1.0, 1.0], [1.0, 2.0], nothing)   # Jv == [-1.0, -1.0]

Cause

src/scimlfunctions.jl (3.58.0; the same lines on master):

• NonlinearFunction{iip}(f::ODEFunction), lines 3406-3417:

  _jvp = iip ? (Jv, u, p) -> (f.jvp(Jv, u, p, Inf); nothing) : (u, p) -> f.jvp(u, p, Inf)
  _vjp = iip ? (vJ, u, p) -> (f.vjp(vJ, u, p, Inf); nothing) : (u, p) -> f.vjp(u, p, Inf)
  

• ODEFunction{iip}(f::NonlinearFunction), lines 3356-3365: (Jv, u, p, t) -> f.jvp(Jv, u, p) and (u, p, t) -> f.jvp(u, p), and the same for vjp.

• The checks that reject them: isinplace(jvp, 4 + argshift, "jvp", iip) in NonlinearFunction{iip, specialize} (line 4777), and isinplace(jvp, 5, "jvp", iip) in ODEFunction{iip, specialize} (line 3191).

The wrappers date from 2022 (8e4bb3ae and #283). The jvp/vjp conversions have no test.

Suggested fix

Pass the vector through in all eight wrappers:

# NonlinearFunction{iip}(f::ODEFunction)
_jvp = iip ? (Jv, v, u, p) -> (f.jvp(Jv, v, u, p, Inf); nothing) : (v, u, p) -> f.jvp(v, u, p, Inf)
_vjp = iip ? (vJ, v, u, p) -> (f.vjp(vJ, v, u, p, Inf); nothing) : (v, u, p) -> f.vjp(v, u, p, Inf)

# ODEFunction{iip}(f::NonlinearFunction)
_jvp = iip ? (Jv, v, u, p, t) -> (f.jvp(Jv, v, u, p); nothing) : (v, u, p, t) -> f.jvp(v, u, p)
_vjp = iip ? (vJ, v, u, p, t) -> (f.vjp(vJ, v, u, p); nothing) : (v, u, p, t) -> f.vjp(v, u, p)

Suggested test: convert both ways, in place and out of place, with jvp and vjp set, and compare the products with the originals at t = Inf. It would fit in test/convert_tests.jl, which converts ODEProblems and SteadyStateProblems but has no conversion with a jvp or vjp set.

Related

We found no existing issue or PR. We searched SciMLBase, NonlinearSolve and SteadyStateDiffEq for "jvp" with "NonlinearFunction", "SteadyStateProblem", "Nonconforming" and "conversion". The nearest is #1430 (merged): it added the λ-shifted arity check (argshift) that these wrappers fail, but it did not touch the wrappers. We work around the bug with a NonlinearProblem method for our own problem type. We are glad to open a PR.