delete timers before services so we don't get warninigs when removing units during dron apply

src/dron/dron.py

@@ -160,6 +160,15 @@ def unit(self) -> str:
 # TODO ugh. not sure how to verify them?
 
 
+def _delete_order(a: Delete) -> int:
+    # systemd warns if we stop/disable a service while its triggering timer is still active.
+    if a.unit.endswith('.timer'):
+        return 0
+    if a.unit.endswith('.service'):
+        return 1
+    return 2
+
+
 def compute_plan(*, current: State, pending: State) -> Plan:
     # eh, I feel like i'm reinventing something already existing here...
     currentd = OrderedDict((x.unit_file, unwrap(x.body)) for x in current)
@@ -239,14 +248,15 @@ def is_always_running(unit_path: Path) -> bool:
     logger.info(f'updating : {len(updates)}')
     logger.info(f'adding   : {len(adds)}')
 
-    for a in deletes:
+    deletes_ordered = sorted(deletes, key=_delete_order)
+
+    for a in deletes_ordered:
         if IS_SYSTEMD:
-            # TODO stop timer first?
             check_call(_systemctl('stop', a.unit))
             check_call(_systemctl('disable', a.unit))
         else:
             launchd.launchctl_unload(unit=Path(a.unit).stem)
-    for a in deletes:
+    for a in deletes_ordered:
         (DRON_UNITS_DIR / a.unit).unlink()
 
     for u, diff in updates:

src/dron/monitor.py

@@ -149,6 +149,9 @@ def update_ui(self) -> None:
                     # hmm seems like DataTable is a bit dumb and even if value is the same, it does costly UI updates...
                     # this is quite noticeable optimization
                     if curr_value != new_value:
+                        # For ~200 rows, update_width=True costs a few extra ms per refresh.
+                        # Keeping it for now because status/next/schedule/command widths can grow, but if refresh
+                        # gets sluggish this is a good first knob to turn off for ordinary cell updates.
                         self.update_cell(row_key=key, column_key=col, value=new_value, update_width=True)
 
         def sort_key(row: list[str]):
@@ -161,6 +164,8 @@ def sort_key(row: list[str]):
         # TODO hmm kinda annoying, doesn't look like it preserves cursor position
         #  if the item pops on top of the list when a service is running?
         #  but I guess not a huge deal now
+        # Sorting 200-ish rows is cheap compared with the DataTable update/render itself
+        # (rough local benchmark: about 1 ms extra), so keep this simple unless row count grows a lot.
         self.sort(key=sort_key)
 
     def show_details_in_pager(self, unit_name: RowKey) -> None:

src/dron/systemd.py

@@ -1,5 +1,6 @@
 from __future__ import annotations
 
+import importlib
 import json
 import os
 import re
@@ -12,7 +13,7 @@
 from pathlib import Path
 from subprocess import PIPE, Popen, run
 from tempfile import TemporaryDirectory
-from typing import Any
+from typing import Any, cast
 from zoneinfo import ZoneInfo
 
 from .api import (
@@ -235,21 +236,18 @@ def _sd(s: str) -> str:
 
 class BusManager:
     def __init__(self) -> None:
-        # unused-ignore because on macos there is no dbus (but this code is still running mypy on CI)
-        from dbus import (  # type: ignore[import-untyped,import-not-found,unused-ignore]  # ty: ignore[unresolved-import]
-            Interface,
-            SessionBus,
-        )
+        # Keep this dynamic because dbus-python is missing on macos; and it's very difficult to convince type checkers to handle that
+        dbus = importlib.import_module('dbus')
 
-        self.Interface = Interface  # meh
+        self.Interface = cast(Any, dbus).Interface  # meh
 
         # NOTE: private=True is important here! Otherwise SessionBus() returns a shared connection.
         # If that connection gets into a broken state (e.g. timeouts), it will persist across BusManager instantiations,
         #   and result in DBusException: org.freedesktop.DBus.Error.NoReply
         # Note that we instantiate BusManager every time we get systemd state, but seems like there is no need to cleanup/close bus, it doesn't seem to leak fds.
-        self.bus = SessionBus(private=True)  # note: SystemBus is for system-wide services
+        self.bus = cast(Any, dbus).SessionBus(private=True)  # note: SystemBus is for system-wide services
         systemd = self.bus.get_object(_sd(''), '/org/freedesktop/systemd1')
-        self.manager = Interface(systemd, dbus_interface=_sd('.Manager'))
+        self.manager = self.Interface(systemd, dbus_interface=_sd('.Manager'))
 
     def properties(self, u: Unit):
         service_unit = self.manager.GetUnit(u)

src/dron/tests/test_dron.py

@@ -7,7 +7,7 @@
 import pytest
 
 from ..common import UnitState
-from ..dron import Add, Delete, Update, compute_plan, do_lint, load_jobs
+from ..dron import Add, Delete, Update, _delete_order, compute_plan, do_lint, load_jobs
 
 
 @pytest.fixture
@@ -134,6 +134,13 @@ def unit(name: str, body: str) -> UnitState:
     ]
 
 
+def test_delete_order_deletes_timers_before_services() -> None:
+    timer = Delete(unit_file=Path('/units/example.timer'))
+    service = Delete(unit_file=Path('/units/example.service'))
+
+    assert sorted([service, timer], key=_delete_order) == [timer, service]
+
+
 def test_jobs_auto_naming(tmp_pythonpath: Path) -> None:
     tpath = Path(tmp_pythonpath) / 'test_drontab.py'
     tpath.write_text(