fix(backup): check the schedule of a host backup job before saving it

.github/scripts/tests/test_backup_schedule_validation.py

@@ -0,0 +1,44 @@
+"""A schedule systemd rejects leaves a timer that never fires and reports no
+error, so the wizard asks for it again instead of saving it."""
+from pathlib import Path
+import subprocess
+import tempfile
+import unittest
+
+SCHEDULER = Path(__file__).resolve().parents[3] / 'scripts/backup_restore/backup_scheduler.sh'
+ANALYZE = '#!/bin/sh\ncase "$2" in "daily 02:00") exit 1;; esac\nexit 0\n'
+
+
+def function(name):
+    text = SCHEDULER.read_text()
+    start = text.index(name + '() {')
+    return text[start:text.index('\n}', start) + 2] + '\n'
+
+
+class ScheduleValidation(unittest.TestCase):
+    def valid(self, expression, **environment):
+        with tempfile.TemporaryDirectory() as directory:
+            analyze = Path(directory) / 'systemd-analyze'
+            analyze.write_text(ANALYZE)
+            analyze.chmod(0o755)
+            return subprocess.run(
+                ['/bin/bash', '-c', function('_calendar_is_valid') + '_calendar_is_valid "$1"', 'test', expression],
+                env={'PATH': f'{directory}:/usr/bin:/bin', **environment},
+            ).returncode == 0
+
+    def test_systemd_decides_what_is_valid(self):
+        self.assertTrue(self.valid('02:30'))
+        self.assertFalse(self.valid('daily 02:00'))
+
+    def test_a_scheduler_without_systemctl_is_not_checked(self):
+        self.assertTrue(self.valid('daily 02:00', PMX_BACKUP_NO_SYSTEMCTL='1'))
+
+    def test_the_wizard_asks_again_before_saving_the_job(self):
+        text = SCHEDULER.read_text()
+        check = text.index('while ! _calendar_is_valid "$on_calendar"; do')
+        self.assertLess(check, text.index('"ON_CALENDAR=$on_calendar"'))
+        self.assertGreater(check, text.index('on_calendar=$(dialog'))
+
+
+if __name__ == '__main__':
+    unittest.main()