systemd: keep the unit type when expanding preset template instances

_parse_preset_entry() hardcoded '.service' when expanding a preset entry that
names template instances, so "enable backup@.timer daily" yielded
backup@daily.service. Harmless while only service presets were consumed; now
that presets are read per unit type, such an entry is attributed to the wrong
type and dropped by the type filter.

Derive the suffix from the matched template unit file instead. No EL8->EL9
preset currently declares template instances for a non-service unit, so this is
a latent fix rather than a behavior change on any supported upgrade path.

Found in review of PR #69.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: 2 people

repos/system_upgrade/common/libraries/systemd.py

@@ -200,10 +200,13 @@ def _parse_preset_entry(entry, presets, load_path):
                 # if the entry contains instance names after template unit name
                 # the entry only applies to the specified instances, not to the
                 # template itself
+                # The instance keeps the unit type of the template it comes from,
+                # which is not necessarily '.service' (e.g. 'backup@.timer').
+                unit_type = os.path.splitext(unit_file)[1]
                 for instance in columns[2:]:
-                    service_name = unit_file[:unit_file.index('@') + 1] + instance + '.service'
-                    if service_name not in presets:  # first occurrence has priority
-                        presets[service_name] = columns[0]
+                    unit_name = unit_file[:unit_file.index('@') + 1] + instance + unit_type
+                    if unit_name not in presets:  # first occurrence has priority
+                        presets[unit_name] = columns[0]
 
             elif unit_file not in presets:  # first occurrence has priority
                 presets[unit_file] = columns[0]

repos/system_upgrade/common/libraries/tests/test_systemd.py

@@ -132,12 +132,18 @@ def readlink_mocked(path):
         'template@instance1.service': 'disable',
         'template@instance2.service': 'disable'
     }),
+    # Instances must keep the template's own unit type, not become '.service'
+    ('enable template@.timer daily weekly', {
+        'template@daily.timer': 'enable',
+        'template@weekly.timer': 'enable'
+    }),
     ('enable globbed*.service', {'globbed-one.service': 'enable', 'globbed-two.service': 'enable'}),
     ('enable example.*', {'example.service': 'enable', 'example.socket': 'enable'}),
     ('disable *', {
             'example.service': 'disable',
             'abc.service': 'disable',
             'template@.service': 'disable',
+            'template@.timer': 'disable',
             'template2@.service': 'disable',
             'globbed-one.service': 'disable',
             'globbed-two.service': 'disable',
@@ -175,6 +181,7 @@ def test_parse_preset_files(monkeypatch):
         'example.socket': 'disable',
         'abc.service': 'disable',
         'template@.service': 'disable',
+        'template@.timer': 'disable',
         'template@instance1.service': 'enable',
         'template@instance2.service': 'enable',
         'globbed-one.service': 'enable',
@@ -267,7 +274,7 @@ def get_system_preset_files_mocked():
     'suffix,expected',
     [
         ('.socket', {'example.socket': 'disable'}),
-        ('.timer', {}),
+        ('.timer', {'template@.timer': 'disable'}),
         (
             '.service',
             {