back-compat: submitted is implicitly required

* Closes cylc#5771.
* Ensure that submit-failed tasks are marked as incomplete.
* See also cylc#5755

cylc/flow/task_pool.py

@@ -1402,7 +1402,7 @@ def remove_if_complete(self, itask):
                   (C7 failed tasks don't count toward runahead limit)
         """
         if cylc.flow.flags.cylc7_back_compat:
-            if not itask.state(TASK_STATUS_FAILED):
+            if not itask.state(TASK_STATUS_FAILED, TASK_OUTPUT_SUBMIT_FAILED):
                 self.remove(itask, 'finished')
             if self.compute_runahead():
                 self.release_runahead_tasks()

tests/functional/spawn-on-demand/19-submitted-compat.t

@@ -0,0 +1,59 @@
+#!/usr/bin/env bash
+# THIS FILE IS PART OF THE CYLC WORKFLOW ENGINE.
+# Copyright (C) NIWA & British Crown (Met Office) & Contributors.
+# 
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU General Public License for more details.
+#
+# You should have received a copy of the GNU General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+#-------------------------------------------------------------------------------
+
+# Test the submitted and submit-failed triggers work correctly in back-compat
+# mode. See https://github.com/cylc/cylc-flow/issues/5771
+
+. "$(dirname "$0")/test_header"
+set_test_number 4
+
+init_workflow "${TEST_NAME_BASE}" << __FLOW__
+[scheduler]
+    [[events]]
+        abort on stall timeout = True
+        stall timeout = PT0S
+
+[scheduling]
+    [[graph]]
+        R1 = """
+            a
+            b
+        """
+
+[runtime]
+    [[a]]  # should complete
+    [[b]]  # should not complete
+        platform = broken
+__FLOW__
+
+mv $WORKFLOW_RUN_DIR/flow.cylc $WORKFLOW_RUN_DIR/suite.rc
+
+workflow_run_fail "${TEST_NAME_BASE}-run" \
+    cylc play "${WORKFLOW_NAME}" --no-detach
+
+grep_workflow_log_ok \
+    "${TEST_NAME_BASE}-back-compat" \
+    'Backward compatibility mode ON'
+grep_workflow_log_ok \
+    "${TEST_NAME_BASE}-a-complete" \
+    '\[1/a running job:01 flows:1\] => succeeded'
+grep_workflow_log_ok \
+    "${TEST_NAME_BASE}-b-incomplete" \
+    "1/b did not complete required outputs: \['submitted', 'succeeded'\]"
+
+purge