ModelingToolkitBase discrete-system tests use SciMLBase without importing it

[ChrisRackauckas-Claude]

Summary

The InterfaceII test group errors twice in ModelingToolkitBase/test/discrete_system.jl because the test file calls SciMLBase.successful_retcode without importing the SciMLBase module.

This reproduces in the OrdinaryDiffEq master IntegrationTest job on Julia 1.10.11:

https://github.com/SciML/OrdinaryDiffEq.jl/actions/runs/31478955487/job/93739213883

The final result is:

Test Summary:                                      | Pass  Error  Broken  Total      Time
InterfaceII                                        | 1036      2       7   1045  24m13.3s
  InterfaceII                                      | 1036      2       7   1045  24m13.3s
    Discrete System                                |   23      2             25     57.8s
ERROR: LoadError: Some tests did not pass: 1036 passed, 0 failed, 2 errored, 7 broken.

The two errors are:

Passing `nothing` to `u0`: Error During Test at .../ModelingToolkitBase/Bhj3l/test/discrete_system.jl:289
  Expression: SciMLBase.successful_retcode(sol)
  UndefVarError: `SciMLBase` not defined

initial conditionsare totermed appropriately: Error During Test at .../ModelingToolkitBase/Bhj3l/test/discrete_system.jl:336
  Expression: SciMLBase.successful_retcode(sol)
  UndefVarError: `SciMLBase` not defined

Reproduction

The failing job checked out:

• OrdinaryDiffEq 9b5ea0b3b4a16b7417b2857efd5a94927c7de193
• ModelingToolkit 92c27bb9fdcaa024ff190feb3d665452e33f9bd8
• Julia 1.10.11
• ModelingToolkit 11.39.0
• ModelingToolkitBase 1.63.0

From the OrdinaryDiffEq checkout, with the ModelingToolkit checkout at downstream:

GROUP=InterfaceII julia +1.10 --project=downstream -e '
using Pkg
Pkg.develop(PackageSpec(path="."))
Pkg.develop(map(path -> Pkg.PackageSpec(; path = joinpath("lib", path)), readdir("lib")))
Pkg.update()
Pkg.test(coverage=true)
'

That is the command and environment used by the linked failing job.

Source boundary and fix direction

The relevant ModelingToolkitBase split commit retained these qualified SciMLBase.successful_retcode references in lib/ModelingToolkitBase/test/discrete_system.jl, but the file has no direct import SciMLBase:

fb2450e

The focused fix should import the owning module in that test file, for example:

import SciMLBase

I applied that one-line change in an isolated checkout, but did not complete a full patched GROUP=InterfaceII Pkg.test run. A standalone include attempt stopped earlier because its environment lacked the Pkg test extra OrdinaryDiffEqFunctionMap; therefore this report does not claim a passing-after result for the patch.