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feat(arrays): Modbus String[]/BitInRegister[] array writes reachable; table follows the resolver

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The Modbus lane (#741 U3) gave the driver String[] and BitInRegister[] holding-register array encoders, and
moved address resolution to ModbusTagAddressResolution (keys first, a bit region coerced to Bool, strict key
reads), but DriverArrayWriteSupport still listed both array shapes read-only (follow-up F1), so a client
write was BadNotWritable before it reached the driver.

Modbus row now mirrors the driver end to end:
- Keys shape only (region + address both present). A string-only addressString tag is resolved by the
  driver with its own family through a parser Core.Abstractions cannot reference, so it stays read-only
  (pinned: the conservative direction).
- Strict reads as the resolver: address an integer 0-65535; a present region / dataType / byteOrder /
  stringByteOrder string must name a member.
- Coils: any dataType (coerced to Bool), <= 1968 coils (FC15).
- HoldingRegisters (FC16, never Bool): numeric, String ((stringLength+1)/2 registers, stringLength >= 1),
  BitInRegister (1 register, bitIndex 0-15, span ending <= 65535), all within maxRegistersPerWrite.
  FC23 is opt-in and never changes the answer.
- Elements convert (ScadaBridge int[] -> Int16 stays writable); only a String / DateTime node over a
  numeric or bit element is left out, since such an element never converts.

Tests: the parity test's PendingF1 exemption and its guard are gone; the parity matrix is now region x
element type x node type against the real WriteAsync with a spec-conformant device (FC15 > 1968 refused),
plus shape edges at every cap boundary (numeric, String, BitInRegister, coil), strict key reads, FC23
on/off, string-only, the ScadaBridge int[] shape and U3 wire bytes. Core.Abstractions row tests and a
composer test (String[] and BitInRegister[] writable; over-cap, no-stringLength and string-only read-only).
Docs: table XML doc, Uns.md, modbus-addressing.md, drivers/Modbus.md, data-plane rules.

Refs #741

Claude-Session: https://claude.ai/code/session_01Ub9hGmYLQvn9XETzw7CMsT
This commit is contained in:
Joseph Doherty
2026-10-22 17:10:00 -04:00
parent 92dea29547
commit 5533de6281
8 changed files with 597 additions and 130 deletions
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.claude/rules/data-plane-auth.md
+3 -2
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@@ -148,8 +148,9 @@ Two things to know before relying on any of this:
`refuseArrayOnScalar` — pass-through drivers keep their browse-committed scalar-shaped array tags writable;
a new sink wrapper must forward that argument, and the reflection guard checks only that the call arrives);
`IndexRange` writes ⇒ `BadWriteNotSupported`, `ValueRank > 1` out of scope. An
array node is writable only when the driver can write the array (`DriverArrayWriteSupport`: Modbus bounded
by `maxRegistersPerWrite`/coil cap, S7 non-Bool/non-wide types, OpcUaClient, Galaxy signed types **with a
array node is writable only when the driver can write the array (`DriverArrayWriteSupport`: Modbus keys-addressed tags bounded
by `maxRegistersPerWrite`/coil cap incl. String/BitInRegister arrays (#741; a string-only `addressString` tag
stays read-only — family unknown at compose time), S7 non-Bool/non-wide types, OpcUaClient, Galaxy signed types **with a
declared `arrayLength`** — an undeclared length stays read-only because a short whole-array write would
resize the Galaxy attribute; AbCip atomic non-BOOL types, AbLegacy Int/Long/Float on the matching data file
(no `/bit`/`.sub`/indirect/`S:`/`I:`/`O:`, not native PLC-5, ≤ 256), TwinCAT every codec type but a BOOL