cylc set: log warning when no outputs specified and task has no required outputs

cylc/flow/id_match.py

@@ -98,7 +98,8 @@ def filter_ids(
             * If IDTokens.Cycle all CyclePoints with any matching tasks will
               be returned.
         warn:
-            Whether to log a warning if no matching tasks are found.
+            Whether to log a warning if no matching tasks are found in the
+            pool.
 
     TODO:
         Consider using wcmatch which would add support for

cylc/flow/task_pool.py

@@ -1943,14 +1943,15 @@ def set_prereqs_and_outputs(
 
         """
         # Get matching pool tasks and inactive task definitions.
-        itasks, inactive_tasks, unmatched = self.filter_task_proxies(
+        itasks, inactive_tasks, _unmatched = self.filter_task_proxies(
             items,
             inactive=True,
             warn_no_active=False,
         )
 
         flow_nums = self._get_flow_nums(flow, flow_descr)
 
+        nothing_set: Set[str] = set()
         # Set existing task proxies.
         for itask in itasks:
             if flow == ['none'] and itask.flow_nums != set():
@@ -1966,7 +1967,8 @@ def set_prereqs_and_outputs(
                 # Spawn as if seq xtrig of parentless task was satisfied,
                 # with associated task producing these outputs.
                 self.check_spawn_psx_task(itask)
-                self._set_outputs_itask(itask, outputs)
+                if not self._set_outputs_itask(itask, outputs):
+                    nothing_set.add(itask.identity)
 
         # Spawn and set inactive tasks.
         if not flow:
@@ -1982,8 +1984,18 @@ def set_prereqs_and_outputs(
                     point, tdef, flow_nums,
                     flow_wait=flow_wait, transient=True
                 )
-                if trans is not None:
-                    self._set_outputs_itask(trans, outputs)
+                if trans is not None and self._set_outputs_itask(
+                    trans, outputs
+                ):
+                    nothing_set.add(trans.identity)
+
+        if nothing_set:
+            msg = "Task has" if len(nothing_set) == 1 else "Tasks have"
+            msg += (
+                " no required outputs to set: "
+                f"{', '.join(sorted(nothing_set))}"
+            )
+            LOG.warning(msg)
 
         if self.compute_runahead():
             self.release_runahead_tasks()
@@ -1992,10 +2004,16 @@ def _set_outputs_itask(
         self,
         itask: 'TaskProxy',
         outputs: List[str],
-    ) -> None:
-        """Set requested outputs on a task proxy and spawn children."""
+    ) -> bool:
+        """Set requested outputs on a task proxy and spawn children.
+
+        Return False if no outputs were specified and the task has no required
+        outputs to set
+        """
         if not outputs:
             outputs = list(itask.state.outputs.iter_required_messages())
+            if not outputs:
+                return False
         else:
             outputs = self._standardise_outputs(
                 itask.point, itask.tdef, outputs
@@ -2018,6 +2036,7 @@ def _set_outputs_itask(
         self.workflow_db_mgr.put_update_task_state(itask)
         self.workflow_db_mgr.put_update_task_outputs(itask)
         self.workflow_db_mgr.process_queued_ops()
+        return True
 
     def _set_prereqs_itask(
         self,
@@ -2316,7 +2335,8 @@ def filter_task_proxies(
             ids:
                 ID strings.
             warn_no_active:
-                Whether to log a warning if no matching active tasks are found.
+                Whether to log a warning if no matching tasks are found in the
+                pool.
             inactive:
                 If True, unmatched IDs will be checked against taskdefs
                 and cycle, and any matches will be returned in the second

tests/integration/scripts/test_set.py

@@ -19,11 +19,21 @@
 Note: see also functional tests
 """
 
+import logging
+
+from cylc.flow.commands import (
+    run_cmd,
+    set_prereqs_and_outputs,
+)
 from cylc.flow.cycling.integer import IntegerPoint
 from cylc.flow.data_messages_pb2 import PbTaskProxy
 from cylc.flow.data_store_mgr import TASK_PROXIES
+from cylc.flow.flow_mgr import FLOW_ALL
 from cylc.flow.scheduler import Scheduler
-from cylc.flow.task_state import TASK_STATUS_SUCCEEDED, TASK_STATUS_WAITING
+from cylc.flow.task_state import (
+    TASK_STATUS_SUCCEEDED,
+    TASK_STATUS_WAITING,
+)
 
 
 async def test_set_parentless_spawning(
@@ -164,3 +174,57 @@ async def test_pre_all(flow, scheduler, run):
         schd.pool.set_prereqs_and_outputs(['1/z'], [], ['all'], ['all'])
         warn_or_higher = [i for i in log.records if i.levelno > 30]
         assert warn_or_higher == []
+
+
+async def test_logging(flow, scheduler, start, log_filter):
+    """Test logging of a mixture of valid and invalid tasks, tasks with
+    some required and no required outputs."""
+    schd: Scheduler = scheduler(
+        flow({
+            'scheduler': {
+                'cycle point format': 'CCYY',
+            },
+            'scheduling': {
+                'initial cycle point': '2000',
+                'graph': {
+                    'R3//P1Y': 'a? & a:x & b? => c?',
+                },
+            },
+            'runtime': {
+                'a': {
+                    'outputs': {'x': 'whatever'}
+                }
+            }
+        })
+    )
+    tasks_to_set = [
+        # Tasks with required outputs:
+        '2000/a',
+        # Tasks without required outputs:
+        '2000/b', '2000/c',
+        # Glob that matches future tasks:
+        '2002/*',
+        # Invalid tasks:
+        '2005/a', '2000/doh',
+    ]
+    async with start(schd):
+        await run_cmd(set_prereqs_and_outputs(schd, tasks_to_set, [FLOW_ALL]))
+
+        assert log_filter(
+            logging.WARNING,
+            "Tasks have no required outputs to set: 2000/a, 2000/b, 2002/a, 2002/b",
+        )
+        assert log_filter(
+            logging.WARNING, "Invalid cycle point for task: a, 2005"
+        )
+        assert log_filter(logging.WARNING, "No matching tasks found: doh")
+        assert len(log_filter(logging.WARNING)) == 3
+
+        # Check singular form of the above message
+        await run_cmd(set_prereqs_and_outputs(schd, ['2000/b'], [FLOW_ALL]))
+
+        assert log_filter(
+            logging.WARNING,
+            "Task has no required outputs to set: 2000/b",
+        )
+        assert len(log_filter(logging.WARNING)) == 4