Fix potential type error & a few small mistakes

cylc/flow/data_store_mgr.py

@@ -116,6 +116,7 @@
 if TYPE_CHECKING:
     from cylc.flow.cycling import PointBase
     from cylc.flow.flow_mgr import FlowNums
+    from cylc.flow.scheduler import Scheduler
 
 EDGES = 'edges'
 FAMILIES = 'families'
@@ -468,7 +469,7 @@ class DataStoreMgr:
     ERR_PREFIX_JOB_NOT_ON_SEQUENCE = 'Invalid cycle point for job: '
 
     def __init__(self, schd, n_edge_distance=1):
-        self.schd = schd
+        self.schd: Scheduler = schd
         self.id_ = Tokens(
             user=self.schd.owner,
             workflow=self.schd.workflow,
@@ -1182,10 +1183,7 @@ def generate_ghost_task(
         t_id = self.definition_id(name)
 
         if itask is None:
-            itask = self.schd.pool.get_task(point_string, name)
-
-        if itask is None:
-            itask = TaskProxy(
+            itask = self.schd.pool.get_task(point_string, name) or TaskProxy(
                 self.id_,
                 self.schd.config.get_taskdef(name),
                 point,
@@ -1226,6 +1224,7 @@ def generate_ghost_task(
             depth=task_def.depth,
             graph_depth=n_depth,
             name=name,
+            flow_nums=serialise_set(flow_nums),
         )
         self.all_n_window_nodes.add(tp_id)
         self.n_window_depths.setdefault(n_depth, set()).add(tp_id)

cylc/flow/task_events_mgr.py

@@ -35,6 +35,7 @@
 from typing import (
     TYPE_CHECKING,
     Any,
+    Callable,
     Dict,
     List,
     NamedTuple,
@@ -437,6 +438,9 @@ class TaskEventsManager():
 
     workflow_cfg: Dict[str, Any]
     uuid_str: str
+    # To be set by the task pool:
+    spawn_func: Callable[['TaskProxy', str], Any]
+
     mail_interval: float = 0
     mail_smtp: Optional[str] = None
     mail_footer: Optional[str] = None
@@ -459,8 +463,6 @@ def __init__(
         self._event_timers: Dict[EventKey, Any] = {}
         # NOTE: flag for DB use
         self.event_timers_updated = True
-        # To be set by the task pool:
-        self.spawn_func = None
         self.timestamp = timestamp
         self.bad_hosts = bad_hosts
 
@@ -1966,7 +1968,7 @@ def reset_bad_hosts(self):
             )
             self.bad_hosts.clear()
 
-    def spawn_children(self, itask, output):
+    def spawn_children(self, itask: 'TaskProxy', output: str) -> None:
         # update DB task outputs
         self.workflow_db_mgr.put_update_task_outputs(itask)
         # spawn child-tasks

cylc/flow/task_pool.py

@@ -742,7 +742,9 @@
         is_xtrig_sequential = False
         if ntask is None:
             # ntask does not exist: spawn it in the flow.
-            ntask = self.spawn_task(tdef.name, point, flow_nums, flow_wait)
+            ntask = self.spawn_task(
+                tdef.name, point, flow_nums, flow_wait=flow_wait
+            )
             # if the task was found set xtrigger checking type.
             # otherwise find the xtrigger type if it can't spawn
             # for whatever reason.
@@ -764,7 +766,12 @@
         # ntask may still be None
         return ntask, is_in_pool, is_xtrig_sequential
 
-    def spawn_to_rh_limit(self, tdef, point, flow_nums) -> None:
+    def spawn_to_rh_limit(
+        self,
+        tdef: 'TaskDef',
+        point: Optional['PointBase'],
+        flow_nums: 'FlowNums',
+    ) -> None:
         """Spawn parentless task instances from point to runahead limit.
 
         Sequentially checked xtriggers will spawn the next occurrence of their
@@ -779,16 +786,14 @@
             return
         if self.runahead_limit_point is None:
             self.compute_runahead()
+            if self.runahead_limit_point is None:
+                return
 
         is_xtrig_sequential = False
         while point is not None and (point <= self.runahead_limit_point):
             if tdef.is_parentless(point):
                 ntask, is_in_pool, is_xtrig_sequential = (
-                    self.get_or_spawn_task(
-                        point,
-                        tdef,
-                        flow_nums
-                    )
+                    self.get_or_spawn_task(point, tdef, flow_nums)
                 )
                 if ntask is not None:
                     if not is_in_pool:
@@ -1329,7 +1334,7 @@
         """
         return self.abort_task_failed
 
-    def spawn_on_output(self, itask, output, forced=False):
+    def spawn_on_output(self, itask: TaskProxy, output: str) -> None:
         """Spawn child-tasks of given output, into the pool.
 
         Remove the parent task from the pool if complete.
@@ -1350,7 +1355,6 @@
 
         Args:
             output: output to spawn on.
-            forced: True if called from manual set task command
 
         """
         if (
@@ -1361,7 +1365,7 @@
             self.abort_task_failed = True
 
         children = []
-        if itask.flow_nums or forced:
+        if itask.flow_nums:
             with suppress(KeyError):
                 children = itask.graph_children[output]
 
@@ -1392,10 +1396,7 @@
             if c_task is not None and c_task != itask:
                 # (Avoid self-suicide: A => !A)
                 self.merge_flows(c_task, itask.flow_nums)
-            elif (
-                c_task is None
-                and (itask.flow_nums or forced)
-            ):
+            elif c_task is None and itask.flow_nums:
                 # If child is not in the pool already, and parent belongs to a
                 # flow (so it can spawn children), and parent is not waiting
                 # for an upcoming flow merge before spawning ... then spawn it.
@@ -1419,7 +1420,10 @@
                     if not in_pool:
                         self.add_to_pool(t)
 
-                    if t.point <= self.runahead_limit_point:
+                    if (
+                        self.runahead_limit_point is not None
+                        and t.point <= self.runahead_limit_point
+                    ):
                         self.rh_release_and_queue(t)
 
                     # Event-driven suicide.
@@ -1659,7 +1663,6 @@
         name: str,
         point: 'PointBase',
         flow_nums: Set[int],
-        force: bool = False,
         flow_wait: bool = False,
     ) -> Optional[TaskProxy]:
         """Return a new task proxy for the given flow if possible.
@@ -1724,7 +1727,7 @@
             if prev_flow_wait:
                 self._spawn_after_flow_wait(itask)
 
-            if itask.transient and not force:
+            if itask.transient:
                 return None
 
         if not itask.transient:
@@ -2017,7 +2020,9 @@
     ):
         """Spawn a future task and set prerequisites on it."""
 
-        itask = self.spawn_task(taskdef.name, point, flow_nums, flow_wait)
+        itask = self.spawn_task(
+            taskdef.name, point, flow_nums, flow_wait=flow_wait
+        )
         if itask is None:
             return
         if self._set_prereqs_itask(itask, prereqs, flow_nums):

tests/integration/test_task_pool.py

@@ -1085,12 +1085,9 @@ async def test_no_flow_tasks_dont_spawn(
                 'R1': 'a => b => c'
             }
         },
-        'scheduler': {
-            'allow implicit tasks': 'true',
-        },
     })
 
-    schd = scheduler(id_)
+    schd: Scheduler = scheduler(id_)
     async with start(schd):
         task_a = schd.pool.get_tasks()[0]
 
@@ -1099,37 +1096,30 @@ async def test_no_flow_tasks_dont_spawn(
 
         # Set as completed: should not spawn children.
         schd.pool.set_prereqs_and_outputs(
-            [task_a.identity], None, None, [FLOW_NONE])
+            [task_a.identity], [], [], [FLOW_NONE]
+        )
+        assert not schd.pool.get_tasks()
 
-        for flow_nums, force, pool in (
+        for flow_nums, expected_pool in (
             # outputs yielded from a no-flow task should not spawn downstreams
-            (set(), False, []),
-            # forced spawning downstream of a no-flow task should spawn
-            # downstreams with flow_nums={}
-            (set(), True, [('1/b', set())]),
+            (set(), []),
             # outputs yielded from a task with flow numbers should spawn
             # downstreams in the same flow
-            ({1}, False, [('1/b', {1})]),
-            # forced spawning should work in the same way
-            ({1}, True, [('1/b', {1})]),
+            ({1}, [('1/b', {1})]),
         ):
             # set the flow-nums on 1/a
             task_a.flow_nums = flow_nums
 
             # spawn on the succeeded output
-            schd.pool.spawn_on_output(
-                task_a,
-                TASK_OUTPUT_SUCCEEDED,
-                forced=force,
-            )
+            schd.pool.spawn_on_output(task_a, TASK_OUTPUT_SUCCEEDED)
 
             schd.pool.spawn_on_all_outputs(task_a)
 
             # ensure the pool is as expected
             assert [
                 (itask.identity, itask.flow_nums)
                 for itask in schd.pool.get_tasks()
-            ] == pool
+            ] == expected_pool
 
 
 async def test_task_proxy_remove_from_queues(