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fix(mtconnect): serve an empty string-typed value as Good "" (#824)

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Owner decision 2026-11-11 (Java parity): a genuinely empty observation on a
String/Reference or unauthored item is Good "" instead of BadNoCommunication.
Non-string items (numeric, bool, DateTime, arrays) keep BadNoCommunication -
the Agent supplied no value; BadTypeMismatch would wrongly blame the authored
type. The UNAVAILABLE sentinel is unchanged, and a structured observation with
no text stays BadNotSupported (structured check now precedes the empty check).
Parity matrix, quality-mapping section and drivers rule updated.

Claude-Session: https://claude.ai/code/session_01GT67AD99zQQqpLCVm3p7xk
This commit is contained in:
Joseph Doherty
2026-11-11 11:56:30 -05:00
parent e857135e8b
commit bdbc47f5fc
4 changed files with 136 additions and 14 deletions
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src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.MTConnect/MTConnectObservationIndex.cs
+25 -6
View File
@@ -76,7 +76,10 @@ internal sealed class MTConnectObservationIndex
private const uint Good = 0x00000000u;
/// <summary>The Agent reported <c>UNAVAILABLE</c>, or supplied no text at all.</summary>
/// <summary>
/// The Agent reported <c>UNAVAILABLE</c>, or supplied no text at all for a non-string item
/// (an empty string-typed item is a Good <c>""</c> — lmxopcua#824).
/// </summary>
private const uint BadNoCommunication = 0x80310000u;
/// <summary>The tag is authored but the Agent has not yet reported it.</summary>
@@ -443,10 +446,8 @@ internal sealed class MTConnectObservationIndex
var serverTimestamp = Now;
var sourceTimestamp = DateTime.SpecifyKind(observation.TimestampUtc, DateTimeKind.Utc);
// No text at all is the degenerate spelling of "no value": MTConnect defines UNAVAILABLE as
// the only way to report absence, so an empty element is not an empty string value.
if (string.IsNullOrWhiteSpace(observation.Value) ||
string.Equals(observation.Value, UnavailableSentinel, StringComparison.Ordinal))
// UNAVAILABLE is MTConnect's one explicit "no value" sentinel — always BadNoCommunication.
if (string.Equals(observation.Value, UnavailableSentinel, StringComparison.Ordinal))
{
return new DataValueSnapshot(null, BadNoCommunication, sourceTimestamp, serverTimestamp);
}
@@ -456,7 +457,7 @@ internal sealed class MTConnectObservationIndex
// Publishing that as a Good string would be noise an operator would trust. Checked before
// the tag lookup because it is a fact about the wire shape, true whether or not the data
// item is authored — and after the sentinel, so an unavailable data set still reports the
// truthful no-comms.
// truthful no-comms, but BEFORE the empty-text test (#824).
if (observation.IsStructured)
{
return new DataValueSnapshot(null, BadNotSupported, sourceTimestamp, serverTimestamp);
@@ -464,6 +465,24 @@ internal sealed class MTConnectObservationIndex
_tags.TryGetValue(observation.DataItemId, out var tag);
// A genuinely EMPTY element (no text, or whitespace the parser trimmed away) is NOT the
// sentinel. Owner decision on lmxopcua#824 (Java parity): on a string-typed item it is a
// Good empty string — an Agent can legitimately report a blank Program/Message/Block.
// An unauthored item coerces as String (below), so it is served the same way.
// On any other type (numeric, Boolean, DateTime, any array) "" cannot be a value, so it
// stays Bad — and stays BadNoCommunication rather than BadTypeMismatch on purpose:
// the Agent supplied no value at all (the same meaning as UNAVAILABLE, just spelled
// degenerately), whereas BadTypeMismatch tells the operator the Agent sent text of the
// wrong type and points them at the tag's authored data type, which is not the fault.
// Checked AFTER the structured test above, so element-children with no text stay
// BadNotSupported rather than becoming a Good "".
if (string.IsNullOrWhiteSpace(observation.Value))
{
return tag is null or { IsArray: false, DriverDataType: DriverDataType.String or DriverDataType.Reference }
? new DataValueSnapshot(string.Empty, Good, sourceTimestamp, serverTimestamp)
: new DataValueSnapshot(null, BadNoCommunication, sourceTimestamp, serverTimestamp);
}
// TIME_SERIES vectors arrive as one whitespace-separated string. Checked AFTER the
// sentinel so an unavailable array tag still reports the truthful no-comms.
if (tag is { IsArray: true })