Driver.Mqtt.Contracts-004/-005/-006/-007.
-004: retainSeed was the last behavioural key read leniently, so "retainSeed":"false"
— what a CSV import produces — silently became the default TRUE, the INVERSE of the
authored intent. Both mappers now read it through TryReadBoolStrict (the qos
absent/valid/present-but-invalid split) and DescribeRejection names it. The authoring
side needed no hand-mirrored rule: MqttTagConfigModel.Validate already consults this
same parse through TagConfigParseGate, so the save is blocked with the inspector's
wording — pinned by a new AdminUI parity theory pair.
-005: the seven [Range] attributes on MqttDriverOptions/MqttPlainOptions never ran —
the options are bound by JsonSerializer, and nothing in the four MQTT projects calls
Validator.TryValidateObject. Two of them CONTRADICTED the real authority (KeepAlive's
[Range(1,…)] forbade the zero Normalize admits as legal MQTT; MaxPayloadBytes' forbade
the non-positive value its own remarks document as falling back to 1 MiB), so wiring
them up would have broken deliberate behaviour. Deleted, with each property naming
where its bound actually lives. The one escape they papered over is closed: an
out-of-range defaultQos rode into the SUBSCRIBE verbatim, and MqttSubscriptionManager's
constructor now clamps it exactly as the AdminUI driver form already persists.
-006: the DateTime write arm cast a negative long to ulong, so 1969-12-31 published a
timestamp ~584 million years in the future; it is now refused as ValueNotRepresentable.
An Unspecified kind was handed to ToUniversalTime(), which reads it as LOCAL — the same
authored instant encoded differently on the two nodes of a redundant pair; it is now
read as UTC.
-007: Format/FormatState enforced only null/empty, and nothing at all on deviceId, so
the type was not round-trip-closed. They now apply the parser's IsValidSegment (plus
'/', which only the format side can see). MqttWriteEncoder's own guards stay — TryEncode
returns an error rather than throwing, and that contract does not change.
A wildcard writeTopic was published verbatim. MQTT-3.3.2-2 forbids a wildcard in a
PUBLISH topic and a conformant broker answers a protocol violation by closing the
connection — which for this driver is the one connection every subscription lives
on, so a single write to a mis-authored tag took the whole driver dark. The
Sparkplug side had the same hole plus a worse one: the binding tuple IS the
NCMD/DCMD topic, so a '/' in groupId/edgeNodeId/deviceId silently addressed a
different edge node than the tag names.
MqttWriteEncoder now refuses both as NoWriteDestination (-> BadNotWritable); the
read path is untouched. metricName is exempt on purpose — it rides in the payload
and Sparkplug's own canonical names use '/'.
MqttTagDefinitionFactory.Inspect gained the matching ADVISORIES (never rejections
— the mappers accept these blobs, and the gate must never be stricter than the
runtime). Both rules were already hard errors in the AdminUI's typed editor, but
that is one authoring path of several: the raw-JSON textarea, CSV import and the
API all reach the deploy gate directly, so the authoring surface was stricter than
the gate — the drift class the #549-#559 arc exists to close.
Shared shape rules single-sourced in the new internal MqttAddressRules.
Driver.Mqtt.Tests 724 (was 708); AdminUI.Tests 1466; ControlPlane.Tests 261.
MqttDriver implemented no IWritable, so every MQTT node materialized read-only
regardless of what the operator authored. It now publishes.
Plain -> the tag's writeTopic; UTF-8 text (Raw/Scalar) or a bare JSON
literal (Json)
Sparkplug -> DCMD for a device metric, NCMD for an edge-node metric, carrying
the metric BY NAME with an explicit Datatype and no seq
Both at QoS 0, retain:false. Retain is deliberately not configurable — a retained
command is replayed by the broker on every future subscribe, including the
device's own reconnect, so one stale write would be re-applied forever.
writeTopic is a new, separate TagConfig key, and its ABSENCE is meaningful: the
write is refused BadNotWritable and the node is discovered ViewOnly. The issue's
"do not skip" warning drove the design — the one outcome worse than read-only
nodes is a node that looks writable, returns Good and publishes nothing. Reusing
the read topic would be worse still: it would echo back and read as a confirmed
device value. Browse-time writability is computed by the SAME encoder the write
path uses, so a node cannot advertise writability it would then refuse.
Good means published, not applied — MQTT has no application-level write ack, so
this is Galaxy's optimistic-Good posture and inherits its property: a failed
DEVICE write can never be surfaced. A failed PUBLISH is reported Bad; the
optimism covers what the device did with the command, never whether it was sent.
WriteIdempotent stays default-off.
The encoder is pure and lives in .Contracts, so both wire shapes are testable
without a broker. Unrepresentable values and types with no Sparkplug encoding are
refused rather than coerced — a Reference must not silently become a String on
the wire, and "not-a-number" must not become 0 on a live plant.
LIVE GATE PASSED against the real Mosquitto fixture on 10.100.0.35: 21/21
integration tests, including 6 new ones that observe the published message with
an INDEPENDENT broker subscriber — a fake asserting "publish was called" could
not tell the feature working from the feature publishing to the wrong topic.
The gate earned its keep: the NCMD test initially failed because NCMD is a SHARED
channel — the driver publishes its own rebirth request (Node Control/Rebirth) on
the very topic an edge-node metric write uses, and it arrived first. Correct
driver behaviour, wrong test; the watcher now matches on metric name. Documented,
because anything consuming that topic needs to know. DCMD has no contention.
Offline: 24 encoder + 9 driver tests. The four new status constants are NAMED so
StatusCodeParityTests can see them (#497/#519) — it went 258 -> 262 and validated
each against the pinned SDK.
Also corrects the Mqtt.md "Known gaps" table: prunes the six rows closed in this
round, and fixes the #507 row, which still described rediscovery as inert after
that issue was closed as superseded and its injection path deleted.
Claude-Session: https://claude.ai/code/session_015p7wGqy3YpZNCpDzTpGMKo
Joseph Doherty