Skip job_queue on machines without a batch system

CrocoDash/case.py

@@ -117,7 +117,9 @@ def __init__(
         ntasks_ocn : int, optional
             Number of tasks for the ocean model. If None, defaults to VisualCaseGen Grid Calculation.
         job_queue: str, optional
-            The queue to submit the CESM case to. If None, defaults to the CESM defaults (usually main)
+            The queue to submit the CESM case to. If None, defaults to the CESM defaults (usually main).
+            Must be one of the machine's queues. Ignored, with a warning, on a machine with no
+            batch system (e.g. ubuntu-latest).
         job_wallclock_time: str, optional
             Must be in the form hh:mm:ss. If None, defaults to the CESM defaults
         """
@@ -1097,20 +1099,34 @@ def _apply_final_xmlchanges(
         xmlchange(
             "MOM6_MEMORY_MODE",
             "dynamic_symmetric",
-            is_non_local=self.cc._is_non_local(),
+            is_non_local=self.is_non_local,
         )
 
-        # xmlchange("ROOTPE_OCN", 128, is_non_local=self.cc._is_non_local()) -> needs to be before the the setup
+        # xmlchange("ROOTPE_OCN", 128, is_non_local=self.is_non_local) -> needs to be before the the setup
         if ntasks_ocn is not None:
-            xmlchange("NTASKS_OCN", ntasks_ocn, is_non_local=self.cc._is_non_local())
+            xmlchange("NTASKS_OCN", ntasks_ocn, is_non_local=self.is_non_local)
         # This will trigger for both the run and the archiver.
         if job_queue is not None:
-            xmlchange("JOB_QUEUE", job_queue, is_non_local=self.cc._is_non_local())
+            # xmlchange rejects a JOB_QUEUE the machine doesn't list, and a
+            # machine with no batch system (e.g. ubuntu-latest) lists none.
+            if self._cime_case.get_value("BATCH_SYSTEM") == "none":
+                print(
+                    f"WARNING: ignoring job_queue={job_queue!r}: machine "
+                    f"{self.machine} has no batch system."
+                )
+            else:
+                queues = self._cime_case.get_env("batch")._get_all_queue_names()
+                if job_queue not in queues:
+                    raise ValueError(
+                        f"job_queue={job_queue!r} is not a queue on machine "
+                        f"{self.machine}. Valid queues: {', '.join(queues) or 'none'}."
+                    )
+                xmlchange("JOB_QUEUE", job_queue, is_non_local=self.is_non_local)
         if job_wallclock_time is not None:
             xmlchange(
                 "JOB_WALLCLOCK_TIME",
                 job_wallclock_time,
-                is_non_local=self.cc._is_non_local(),
+                is_non_local=self.is_non_local,
             )
 
     def validate_case(self):

tests/test_case.py

@@ -133,6 +133,50 @@ def test_coupling_interval_rejects_uneven_ncpl():
         _stub_case_for_ncpl(7, 5450.0)._coupling_interval("ICE")
 
 
+def _stub_case_for_xmlchanges(monkeypatch, batch_system, queues):
+    """A Case with only what _apply_final_xmlchanges reads; returns it and
+    the xml variables it changes."""
+    from types import SimpleNamespace
+    import CrocoDash.case as case_mod
+
+    changed = {}
+    monkeypatch.setattr(
+        case_mod, "xmlchange", lambda var, val, **kw: changed.update({var: val})
+    )
+    case = case_mod.Case.__new__(case_mod.Case)
+    case.machine = "some-machine"
+    case.is_non_local = False
+    batch = SimpleNamespace(_get_all_queue_names=lambda: queues)
+    case._cime_case = SimpleNamespace(
+        get_value={"BATCH_SYSTEM": batch_system}.__getitem__,
+        get_env={"batch": batch}.__getitem__,
+    )
+    return case, changed
+
+
+@pytest.mark.parametrize(
+    "batch_system, queues, expected",
+    [
+        ("pbs", ["develop", "main"], "develop"),
+        ("none", [], None),  # ubuntu-latest: xmlchange rejects any queue
+    ],
+)
+def test_job_queue_is_set_only_on_a_machine_with_a_batch_system(
+    monkeypatch, batch_system, queues, expected
+):
+    case, changed = _stub_case_for_xmlchanges(monkeypatch, batch_system, queues)
+    case._apply_final_xmlchanges(job_queue="develop", job_wallclock_time="01:00:00")
+    assert changed.get("JOB_QUEUE") == expected
+    assert changed["JOB_WALLCLOCK_TIME"] == "01:00:00"
+
+
+def test_an_unknown_job_queue_lists_the_valid_ones(monkeypatch):
+    case, changed = _stub_case_for_xmlchanges(monkeypatch, "pbs", ["develop", "main"])
+    with pytest.raises(ValueError, match="Valid queues: develop, main"):
+        case._apply_final_xmlchanges(job_queue="mian")
+    assert "JOB_QUEUE" not in changed
+
+
 def test_a_configuration_error_raises_instead_of_returning_a_half_built_case(
     CrocoDash_case_factory, tmp_path, monkeypatch
 ):