upgrades: Simplify dist upgrades checks using exceptions

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

plinth/modules/upgrades/__init__.py

@@ -221,9 +221,23 @@ def try_start_dist_upgrade(test=False):
     """Try to start dist upgrade."""
     from plinth.notification import Notification
 
-    result = privileged.start_dist_upgrade(test)
-    dist_upgrade_started = result['dist_upgrade_started']
-    reason = result['reason']
+    try:
+        privileged.start_dist_upgrade(test, _log_error=False)
+    except RuntimeError as exception:
+        reason = exception.args[0]
+    else:
+        logger.info('Started dist upgrade.')
+        title = gettext_noop('Distribution update started')
+        message = gettext_noop(
+            'Started update to next stable release. This may take a long '
+            'time to complete.')
+        Notification.update_or_create(id='upgrades-dist-upgrade-started',
+                                      app_id='upgrades', severity='info',
+                                      title=title, message=message, actions=[{
+                                          'type': 'dismiss'
+                                      }], group='admin')
+        return
+
     if 'found-previous' in reason:
         logger.info(
             'Found previous dist-upgrade. If it was interrupted, it will '
@@ -250,20 +264,8 @@ def try_start_dist_upgrade(test=False):
                                       title=title, message=message, actions=[{
                                           'type': 'dismiss'
                                       }], group='admin')
-    elif 'started-dist-upgrade' in reason:
-        logger.info('Started dist upgrade.')
-        title = gettext_noop('Distribution update started')
-        message = gettext_noop(
-            'Started update to next stable release. This may take a long '
-            'time to complete.')
-        Notification.update_or_create(id='upgrades-dist-upgrade-started',
-                                      app_id='upgrades', severity='info',
-                                      title=title, message=message, actions=[{
-                                          'type': 'dismiss'
-                                      }], group='admin')
     else:
-        logger.warning('Unhandled result of start-dist-upgrade: %s, %s',
-                       dist_upgrade_started, reason)
+        logger.warning('Unhandled result of start-dist-upgrade: %s', reason)
 
 
 def is_backports_requested():

plinth/modules/upgrades/distupgrade.py

@@ -75,7 +75,7 @@ def _get_new_codename(test_upgrade: bool) -> str | None:
     return None
 
 
-def check(test_upgrade=False) -> tuple[bool, str]:
+def check(test_upgrade=False):
     """Check if a distribution upgrade be performed.
 
     Check for new stable release, if updates are enabled, and if there is
@@ -87,30 +87,28 @@ def check(test_upgrade=False) -> tuple[bool, str]:
     if not.
     """
     if action_utils.service_is_running('freedombox-dist-upgrade'):
-        return (True, 'found-previous')
+        raise RuntimeError('found-previous')
 
     from plinth.modules.upgrades import get_current_release
     release, dist = get_current_release()
     if release in ['unstable', 'testing', 'n/a']:
-        return (False, f'already-{release}')
+        raise RuntimeError(f'already-{release}')
 
     codename = _get_new_codename(test_upgrade)
     if not codename:
-        return (False, 'codename-not-found')
+        raise RuntimeError('codename-not-found')
 
     if codename == dist:
-        return (False, f'already-{dist}')
+        raise RuntimeError(f'already-{dist}')
 
     if not utils.check_auto():
-        return (False, 'upgrades-not-enabled')
+        raise RuntimeError('upgrades-not-enabled')
 
     if not utils.is_sufficient_free_space():
-        return (False, 'not-enough-free-space')
+        raise RuntimeError('not-enough-free-space')
 
     _sources_list_update(dist, codename)
 
-    return (True, 'started-dist-upgrade')
-
 
 @contextlib.contextmanager
 def _snapshot_run_and_disable() -> Generator[None, None, None]:

plinth/modules/upgrades/privileged.py

@@ -236,7 +236,7 @@ def activate_backports(develop: bool = False):
 
 
 @privileged
-def start_dist_upgrade(test: bool = False) -> dict[str, str | bool]:
+def start_dist_upgrade(test: bool = False):
     """Start dist upgrade process.
 
     Check if a new stable release is available, and start dist-upgrade process
@@ -244,11 +244,8 @@ def start_dist_upgrade(test: bool = False) -> dict[str, str | bool]:
     """
     _release_held_freedombox()
 
-    upgrade_ready, reason = distupgrade.check(test)
-    if upgrade_ready:
-        distupgrade.start_service()
-
-    return {'dist_upgrade_started': upgrade_ready, 'reason': reason}
+    distupgrade.check(test)
+    distupgrade.start_service()
 
 
 @privileged