Add xtrigger CYLC_PYTHONPATH functional test

Ensures that xtrggers in your CYLC_PYTHONPATH
are respected above entry_point xtriggers.

tests/functional/xtriggers/04-respect-cylc-pythonpath.t

@@ -0,0 +1,47 @@
+#!/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 persistence of xtrigger results across restart. A cycling task depends
+# on a non cycle-point dependent custom xtrigger called "faker". In the first
+# cycle point the xtrigger succeeds and returns a result, then a task shuts
+# the workflow down.  Then we replace the custom xtrigger function with one that
+# will fail if called again - which should not happen because the original
+# result should be remembered (as this xtrigger is not cycle point dependent).
+# Also test the correct result is broadcast to the dependent task before and
+# after workflow restart.
+
+. "$(dirname "$0")/test_header"
+set_test_number 3
+
+install_workflow "${TEST_NAME_BASE}" "${TEST_NAME_BASE}"
+
+# Install the succeeding xtrigger function.
+export CYLC_PYTHONPATH=${WORKFLOW_RUN_DIR}/dir:${CYLC_PYTHONPATH:-}
+
+# Validate the test workflow.
+run_ok "${TEST_NAME_BASE}-val" cylc validate --debug "${WORKFLOW_NAME}"
+
+# Run the first cycle, till auto shutdown by task.
+TEST_NAME="${TEST_NAME_BASE}-run"
+workflow_run_ok "${TEST_NAME}" cylc play --no-detach --debug "${WORKFLOW_NAME}"
+
+# Check the broadcast result of xtrigger.
+cylc cat-log "${WORKFLOW_NAME}" >'scheduler.log.out'
+grep_ok "echo overridden, args=('the_args',)" 'scheduler.log.out'
+
+purge

tests/functional/xtriggers/04-respect-cylc-pythonpath/dir/echo.py

@@ -0,0 +1,21 @@
+#!/usr/bin/env python3
+# 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/>.
+
+
+def echo(*args, **kwargs):
+    print(f"echo overridden, args={args}")
+    return (True, {})

tests/functional/xtriggers/04-respect-cylc-pythonpath/flow.cylc

@@ -0,0 +1,15 @@
+[scheduler]
+    cycle point format = %Y
+[scheduling]
+    initial cycle point = 2010
+    final cycle point = 2011
+    [[xtriggers]]
+        x1 = echo("the_args")
+    [[graph]]
+        R1 = "@x1 => foo => shutdown"
+        P1Y = "@x1 => foo"
+[runtime]
+    [[foo]]
+        script = true
+    [[shutdown]]
+        script = "cylc shutdown $CYLC_WORKFLOW_ID"