daemon: When ensuring running state handle not-installed state

Tests:

- Uninstall miniflux and postgresql. Install freshly with all the patches in
this series. When installing miniflux freshly, postgresql is not disabled soon
after miniflux package is installed. Without this patch, postgresql is disabled
after packages are installed leading to a setup failure.

Signed-off-by: Sunil Mohan Adapa <sunil@medhas.org>
Reviewed-by: James Valleroy <jvalleroy@mailbox.org>

plinth/daemon.py

@@ -91,6 +91,13 @@ class Daemon(app.LeaderComponent, log.LogEmitter):
     def ensure_running(self):
         """Ensure a service is running and return to previous state."""
         from plinth.privileged import service as service_privileged
+
+        if action_utils.service_show(self.unit)['LoadState'] == 'not-found':
+            # The service's package not installed yet, don't try to start it
+            # and later stop it after it is installed.
+            yield False  # Not running
+            return
+
         starting_state = self.is_running()
         if not starting_state:
             service_privileged.enable(self.unit)

plinth/tests/test_daemon.py

@@ -145,12 +145,21 @@ def test_is_running(service_is_running, daemon):
 
 @patch('plinth.app.apps_init')
 @patch('plinth.action_utils.service_is_running')
+@patch('plinth.action_utils.service_show')
 @patch('subprocess.run')
-def test_ensure_running(subprocess_run, service_is_running, apps_init,
-                        app_list, mock_privileged, daemon):
+def test_ensure_running(subprocess_run, service_show, service_is_running,
+                        apps_init, app_list, mock_privileged, daemon):
     """Test that checking that the daemon is running works."""
     common_args = dict(stdout=subprocess.PIPE, stderr=subprocess.PIPE,
                        check=False)
+
+    service_show.return_value = {'LoadState': 'not-found'}
+    with daemon.ensure_running() as starting_state:
+        assert not starting_state
+        assert subprocess_run.mock_calls == []
+
+    service_show.return_value = {'LoadState': 'loaded'}
+
     service_is_running.return_value = True
     with daemon.ensure_running() as starting_state:
         assert starting_state