Post-implementation review (HIGH finding) noted #478's mux-delivered
input-quality path does not cover a driver comms-loss: a poll driver
(Modbus/S7) whose device goes unreachable emits only ConnectivityChanged and
goes silent on the value feed, so a scripted alarm keeps the last Good value.
The code as shipped faithfully implements #478's written scope (worst of input
tags' qualities via the dependency mux). The comms-loss bridge for scripted
alarms (symmetric of native #477-L2, plus the null-value/cold-start asymmetry
and its VT-quality ripple) is tracked as #481. Docs updated in
AlarmTracking.md + the design doc.
Layer 3 of #477: a scripted alarm's condition Quality now reflects the WORST
quality across its input tags, mirroring the native OT semantic (#477 L2).
Plumbing (quality was silently discarded twice on the live path):
- VirtualTagActor.DependencyValueChanged gains Quality (defaulted Good); the
DependencyMuxActor forwards the published AttributeValuePublished.Quality it
already carried; ScriptedAlarmHostActor.OnDependencyChanged pushes the real
quality into the engine (was hardcoded 0u/Good).
Engine (Core.ScriptedAlarms):
- ScriptedAlarmEngine computes worst-of-input quality each eval (skipping
not-yet-published inputs, which are a readiness concern, not a quality signal)
and carries it on ScriptedAlarmEvent.WorstInputStatusCode.
- A real transition carries the current worst quality so ToSnapshot's full
snapshot doesn't clobber quality back to Good (e.g. transition while Uncertain).
- A Bad input freezes the condition (no transition), like a comms-lost native
driver; a quality-bucket change with no transition emits the new
EmissionKind.QualityChanged, routed to the existing #477-L2
AlarmQualityUpdate -> WriteAlarmQuality node path (quality only, no /alerts
row, no historian write). ScriptedAlarmSource skips QualityChanged so it never
fabricates a phantom IAlarmSource event.
Host: ToSnapshot maps WorstInputStatusCode -> OpcUaQuality; OnEngineEmission
routes QualityChanged out of band.
Tests (TDD, RED-first): engine worst-carry + Bad/restore QualityChanged +
unchanged-bucket-no-emit; source swallows QualityChanged; mux forwards quality;
host Bad-dep -> AlarmQualityUpdate(no alerts) + transition snapshot carries worst.
Docs: AlarmTracking.md Layer-3 section + design doc.
Closes#478
Joseph Doherty