[Detail Bug] KNX GUI: Com Flags table and node pins disappear after parameter change switches a <choose> branch

Detail Bug Report

https://app.detail.dev/org_62aa40f5-2c23-4914-a665-3bb2068af20e/bugs/bug_1244263a-b1ed-4540-bf32-9804bab35c46

Introduced in 5b212db9eb994f7971076c5afb80d62d2a4d5d3e by @kewde on Jun 19, 2026

Summary

• Context: Device (apps/knx-gui/src/knx_gui/device.py) wraps an Application and exposes its dynamic KNX com objects to the Configure panel's Com Flags table and the node editor via device.get_visible_com_objects() / device.rows.
• Bug: Device.com_objects is captured once at construction time from the currently-visible UI tree, so com objects that a later parameter change reveals via a ComObjectParameterChoose/ChannelChoose branch switch are never added to com_objects, and get_visible_com_objects() only iterates that stale snapshot — newly-revealed com objects silently vanish from the panel.
• Actual vs. expected: After the user edits a parameter that switches a <choose> branch, the Com Flags table and node editor should show the newly-revealed com objects; instead get_visible_com_objects() returns the intersection of the old snapshot with the new UI tree, which is empty when the branch switch replaces the whole com-object set — the Com Flags table renders "Com Flags (0)" and the node editor renders no pin rows.
• Impact: After a parameter edit that switches a <choose> branch, com objects belonging to the newly-active branch are not in Device.com_objects, so get_visible_com_objects() drops them and the Com Flags table renders "Com Flags (0)" / the node editor renders no pin rows.

Code with Bug

apps/knx-gui/src/knx_gui/device.py

def __post_init__(self) -> None:
    if self.app.program.dynamic is not None:
        ...
        self._dynamic_ui = _DynamicUI(...)
    if not self.com_objects:
        self.com_objects = self._create_com_objects_from_app()  # <-- BUG 🔴 one-shot snapshot of currently-visible UiComObjects

def get_visible_com_objects(self) -> list[ComObject]:
    if self._cached_visible_cos is not None:
        return self._cached_visible_cos
    if self._dynamic_ui is None:
        return list(self.com_objects)
    ui_cos = _collect_ui_com_objects(self._dynamic_ui.ui())
    ui_by_id = {co.ref_id: co for co in ui_cos}
    result: list[ComObject] = []
    for co in self.com_objects:                  # <-- BUG 🔴 iterates the stale snapshot, not ui_cos
        ui_co = ui_by_id.get(co.id)
        if ui_co is None:
            continue                             # <-- BUG 🔴 a newly-revealed co is never created/appended
        co.name = ui_co.name
        ...
        result.append(co)
    self._cached_visible_cos = result
    return result

def set_param_value(self, ref_id: str, value: str) -> None:
    if self._dynamic_ui is not None:
        self._dynamic_ui.set_parameter_ref(ref_id, value)
        self._cached_visible_cos = None
        self._cached_rows = None                 # <-- BUG 🔴 com_objects is not regenerated, so the next get_visible_com_objects still filters the old snapshot

Explanation

• DynamicUI.set_parameter_ref() invalidates the dynamic UI tree cache (self._ui = None), so the next self._dynamic_ui.ui() correctly re-evaluates the <choose> branch and returns the newly-active set of UiComObjects.
• However, Device.com_objects is a one-time snapshot taken during Device construction from the then-active branch. After a branch switch, get_visible_com_objects() only filters and updates those stale ComObject instances; it never creates/appends ComObjects for newly-emitted UiComObjects. If the branch switch replaces the whole com-object set, all old snapshot entries are filtered out, producing [], so the Configure panel shows "Com Flags (0)" and the node editor shows no pin rows.

Codebase Inconsistency

apps/knx-gui/src/knx_gui/plugins/project/service.py intentionally updates the live Device in-place on parameter edits (no rebuild), which makes the stale snapshot observable:

def set_param(self, device: Device, param_id: str, value: str) -> None:
    if self._pid is None:
        return
    self._svc.set_parameter(self._pid, device.node_id, param_id, value)
    ...
    device.set_param_value(param_id, value)

Recommended Fix

Regenerate the com_objects snapshot inside set_param_value (after set_parameter_ref) and merge by com-object ref-id so persistent com objects keep their existing instance (and db_id) while newly-revealed com objects are created:

def set_param_value(self, ref_id: str, value: str) -> None:
    if self._dynamic_ui is not None:
        self._dynamic_ui.set_parameter_ref(ref_id, value)
        self.com_objects = self._refresh_com_objects_with_db_id_preserved()  # FIX 🟢
        self._cached_visible_cos = None
        self._cached_rows = None

History

This bug was introduced in commit 5b212db. That commit reworked Device._create_com_objects_from_app to source the com_objects snapshot from the live dynamic UI tree (self._dynamic_ui.ui(), which only emits the currently-selected <choose> branch's com objects) instead of the static self.app.com_objects() list (which carried com objects from every branch). The intent was to back Device with the project DB's module_instances/parameter_instance_refs so a rebuild faithfully reproduces the user's selected topology — but the change left set_param_value only calling self._dynamic_ui.set_parameter_ref(...) and zeroing the visibility cache, without ever regenerating self.com_objects. Combined with the in-place (no-_bump()), set_param path that the earlier commit 09f490434 had already established as the call site, the snapshot goes stale the moment a branch-switching parameter is edited: the live ui() flips to the alternate branch, but self.com_objects still holds the default-branch refs, so get_visible_com_objects's if ui_co is None: continue match drops every entry and the panel goes blank. The bug was unobservable before 5b212db because the pre-existing static-source snapshot deliberately contained com objects from every branch, so a stale snapshot still covered the newly-revealed ones.

Start in apps/knx-gui/src/knx_gui/device.py, reading post_init, set_param_value, get_visible_com_objects, and _create_com_objects_from_app. Trace the parameter-edit path from apps/knx-gui/src/knx_gui/plugins/project/service.py and inspect how DynamicUI.set_parameter_ref refreshes the UI tree. Done means switching a branch preserves existing database IDs and makes the newly revealed com objects appear in the Com Flags table and node editor.