IWritable shipped behind write.enabled and docs/drivers/MTConnect.md told the operator to
set it, but MTConnectDriverForm — the only editor DriverFormMaps maps for this type, with
no raw-JSON escape hatch and no driver-instance API — exposed no write section, so the
documented enablement path was a hand edit of DriverInstance.DriverConfig in the config DB.
- Write-back section: switch + form text stating it is observation injection, that the
Agent's AllowPut is an independent second gate, and that it does not by itself make a
node writable over OPC UA (Tag.AccessLevel still composes CurrentWrite).
- Write added to the mirrored MTConnectConfigDto and to the form model, written in BOTH
states — an omitted block would leave a previously-authored true standing, so the switch
could never turn writing off again.
- The false 'MTConnect is read-only' header comment is gone; the doc names the new section.
No bUnit here, so the model/serialization seam is unit-tested both sides: the AdminUI test
pins the emitted bytes, and MTConnectFactoryTests parses that same document and asserts
MTConnectDriverOptions.Write.Enabled. Live page verification remains a rig step.
MTConnectDriver now implements IWritable over the Task-1 agent-client seam
(WriteObservationAsync -> the Agent's AllowPut POST surface). A write is
OBSERVATION INJECTION, not machine command: it sets what the Agent reports for
a DataItem, is visible to every consumer of that Agent, and is overwritten by
the next adapter/SHDR update. Off at two independent gates, both off by default
- the Agent's own AllowPut and the driver's write.enabled (Task 0).
Per-slot refusal order (never throws, strict N-in/N-out batch shape):
write disabled -> BadNotWritable
no live client -> BadNotConnected (ReadAsync's existing convention)
reference unresolved -> BadNodeIdUnknown
no resolvable device -> BadNodeIdUnknown
CONDITION category -> BadNotWritable
null / non-scalar value -> BadTypeMismatch
agent refusal OR throw -> BadCommunicationError
OperationCanceledException fills the remaining slots and returns. The Agent's
refusal text is logged at Warning and never enters DriverHealth.LastError
(type-only discipline); a refused write leaves health untouched.
Device-name resolution: TagBinding gains WriteTargetsByDataItemId, built in
BuildBinding from a probe-model walk that remembers which device each DataItem
was declared under (name, or id when nameless) plus its category. Falls back to
options.DeviceName; unresolvable -> BadNodeIdUnknown rather than a guess.
Values render via Convert.ToString(..., InvariantCulture) - so a Boolean writes
the invariant string "True"/"False", NOT "1"/"0". Arrays are refused rather
than rendered: Convert.ToString would emit the literal "System.Double[]", which
the Agent stores happily and which is invisible until read-back.
FINDING - the CurrentWrite bit does NOT key on SecurityClassification, and the
discovery stamping below is therefore cosmetic. Traced end to end: a browsed
leaf's SecurityClass survives into the browse session's AttributeInfo
(CapturedTreeBrowseSession.cs:53) and stops there - RawBrowseModal never reads
it, RawBrowseCommitMapper.MapLeaf hardcodes TagAccessLevel.Read, and Tag has no
SecurityClass column. AddressSpaceComposer:746/:809 sets Writable purely from
Tag.AccessLevel == ReadWrite; AddressSpaceApplier ANDs !IsArray;
OtOpcUaNodeManager.ComposeAccessLevel:2002 composes CurrentWrite from that
alone. Driver capability is never consulted at compose time either - IWritable
is checked only at runtime in DriverInstanceActor:755. Consequences: (a) raw
tags already committed keep their authored AccessLevel, so nothing this commit
does makes an existing node writable; (b) an operator must still set the tag to
ReadWrite for an MTConnect write to be reachable over OPC UA; (c) conversely a
ReadWrite tag on a non-IWritable driver has always advertised CurrentWrite and
failed only at the actor - pre-existing, not touched here.
Discovery stamps CanWrite(writeEnabled, dataItem) = write.enabled && !CONDITION
-> Operate, else ViewOnly - kept honest so the browse never advertises a tier
the write path would refuse (MQTT's CanWrite principle), with the caveat above
recorded verbatim at the call site.
Status-code constants are spelled WITHOUT MqttDriver's "Status" prefix, to
match the two this file already declares (BadCommunicationError,
BadNotConnected). StatusCodeParityTests strips either spelling and passes.
TDD: WriteAsync landed first as a NotImplementedException scaffold - 19 of 20
new tests red on behaviour, 1 (the capability assertion) green on the scaffold
- then implemented. MTConnectFactoryTests' "not_writable" characterization test
is rewritten to pin the new truth, and is the guard for the concrete-return
contract the factory remark explains.
Tests: 532 passed / 0 failed (was ~509). Full solution build: 0 errors,
0 warnings; OTOPCUA0001 clean.
The factory carries NO config DTO of its own: CreateInstance delegates to
MTConnectDriver.ParseOptions, the single authority for the config document.
A second DTO would drift from the parse the runtime's ReinitializeAsync path
uses, and the drift would only surface at deploy time.
Construction is connection-free (agentClientFactory: null) because the Wave-0
universal browser builds a throwaway instance per browse probe, and the
returned instance is never narrowed — its five capability interfaces ARE the
runtime's dispatch surface. Pinned by tests asserting all five plus the
deliberate absence of IWritable.
DriverTypeName is the literal "MTConnect"; Task 16 adds DriverTypeNames.MTConnect
and the host registration that must equal it.
Joseph Doherty