Fix GDPopt LBB time-limit results

[bernalde]

Summary

• Replace GDPopt LBB's stale _get_final_results_object() call on the time-limit path with _get_final_pyomo_results_object().
• Add a solver-independent LBB regression test that forces the time-limit branch and verifies maxTimeLimit results.
• Add MindtPy GOA time-limit coverage to verify its inherited GOA path sets maxTimeLimit on SolverResults.

Tests run

• pytest -q pyomo/contrib/gdpopt/tests/test_LBB.py::TestGDPopt_LBB_TimeLimit::test_time_limit_returns_pyomo_results_object pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py::TestMindtPyGOATimeLimit::test_goa_time_limit_sets_solver_results_condition - passed, 2 passed in 0.52s
• pytest -q pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 32 passed, 9 skipped, 2 deselected in 1.86s
• python -m black --check --diff pyomo/contrib/gdpopt/branch_and_bound.py pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 3 files would be left unchanged
• git diff --check -- pyomo/contrib/gdpopt/branch_and_bound.py pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed

Notes about tests not run

• Full repository pytest and full-repository Black were not run locally because the targeted change is narrow and the full CI matrix covers multiple Python versions, platforms, optional solver installs, documentation, and coverage jobs.

Closes #3941

[bernalde]

Review summary

1. Blocking issues: none.
2. Nonblocking issues: none.
3. Questions: none.
4. Tests run:
   • pytest -q pyomo/contrib/gdpopt/tests/test_LBB.py::TestGDPopt_LBB_TimeLimit::test_time_limit_returns_pyomo_results_object pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py::TestMindtPyGOATimeLimit::test_goa_time_limit_sets_solver_results_condition - passed, 2 passed in 0.50s.
   • pytest -q pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 32 passed, 9 skipped, 2 deselected in 1.69s.
   • python -m black --check --diff pyomo/contrib/gdpopt/branch_and_bound.py pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 3 files unchanged. Black emitted its Python 3.13 / Python 3.14 parser warning but completed successfully.
   • git diff --check upstream/main...HEAD -- pyomo/contrib/gdpopt/branch_and_bound.py pyomo/contrib/gdpopt/tests/test_LBB.py pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed.
   • gh pr checks 3942 --repo Pyomo/pyomo - currently pending overall. Passing at review time: Read the Docs, lint/style-and-typos, linux/3.10/bare-env, linux/3.10/slim, linux/3.11/mpi, linux/3.12/numpy2. Remaining GitHub Actions matrix jobs and Jenkins inspection are still pending.
5. Merge as-is: I do not see code changes needed from review, but I would wait for the pending required CI/Jenkins statuses before merging.

[bernalde]

Coordination note for #3946:

This PR and #3946 fix different bugs. This one fixes the LBB time-limit result path for #3941; #3946 fixes continuous-node solver dispatch for #3945. #3946 does not supersede this PR.

I checked the combined patches with git merge-tree. The runtime changes are independent, but both PRs add imports/tests near the top of pyomo/contrib/gdpopt/tests/test_LBB.py, so the second PR merged will likely need a small conflict resolution there.

Recommendation: merge this PR first since it is smaller and already through the GitHub Actions matrix, then refresh/rebase #3946 afterward.

[emma58]

In the long run we should think about moving the GDPopt solvers onto the new contrib.solver results object, but this looks good for now--it fixes a dumb bug in LBB leftover from a long ago GDPopt rewrite.

[emma58]

Can you move the import to the top of the file?

[bernalde]

Addressed in ede4b3787 by moving MindtPy_GOA_Solver to the file-level imports in pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py. The GOA regression still passes with pytest -q pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py::TestMindtPyGOATimeLimit::test_goa_time_limit_sets_solver_results_condition.

[bernalde]

Review comments addressed.

Commits pushed:

• ede4b3787 - Address MindtPy GOA test import review

Main changes made:

• Moved MindtPy_GOA_Solver import from inside test_goa_time_limit_sets_solver_results_condition() to the top-level import block in pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py.

Tests run:

• pytest -q pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py::TestMindtPyGOATimeLimit::test_goa_time_limit_sets_solver_results_condition - passed, 1 passed in 0.79s.
• pytest -q pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 29 passed in 1.59s.
• pytest -q pyomo/contrib/gdpopt/tests/test_LBB.py::TestGDPopt_LBB_TimeLimit::test_time_limit_returns_pyomo_results_object pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py::TestMindtPyGOATimeLimit::test_goa_time_limit_sets_solver_results_condition - passed, 2 passed in 0.57s.
• python -m black --check --diff pyomo/contrib/mindtpy/tests/test_mindtpy_no_discrete.py - passed, 1 file unchanged. Black emitted its Python 3.13 / Python 3.14 parser warning but completed successfully.

Comments intentionally not addressed:

• The contrib.solver migration note was not addressed in this PR. The review described it as a long-run direction and approved the current bugfix. Migrating GDPopt and/or MindtPy result handling to contrib.solver is broader than the LBB stale-helper fix in GDPopt LBB time-limit path calls stale _get_final_results_object #3941. Related MindtPy tracking exists in MindtPy follow-up: evaluate contrib.solver migration for direct continuous solves #3936; no GDPopt-specific open issue turned up in a quick search.

Remaining risks or follow-up items:

• Consider broadening MindtPy follow-up: evaluate contrib.solver migration for direct continuous solves #3936 or opening a sibling GDPopt issue for the longer-term contrib.solver migration work.

[mrmundt]

@bernalde - Required legal acknowledgement was deleted and tests are failing. Please feel free to reopen with the correct template once tests are passing.

[bernalde]

Replaced by #4010.

This PR was closed because its description did not follow the repository pull request template — the AI-Use Disclosure and Legal Acknowledgement sections were absent. GitHub would not allow it to be reopened, so the work continues in a new PR.

#4010 carries over the implementation and tests from here unchanged, rebased onto current main, with a description built from .github/PULL_REQUEST_TEMPLATE.md with all sections intact.

For reference, the fix is still needed: pyomo/contrib/gdpopt/branch_and_bound.py on current main still calls the stale _get_final_results_object() on the LBB time-limit path, while the other termination site in the same file already uses _get_final_pyomo_results_object(). Issue #3941 remains open.

@emma58's approving review on this PR is the reason #4010 was prioritized first among the replacements. That approval does not transfer to the new PR, so #4010 needs a fresh review. The discussion here remains the historical record; this branch was left untouched so the diff stays readable.