# Code Review — Driver.FOCAS.Contracts

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| Field | Value |
|---|---|
| Module | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts` |
| Reviewer | Claude Code |
| Review date | 2026-06-19 |
| Commit reviewed | `7286d320` |
| Status | Reviewed |
| Open findings | 0 |

## Checklist coverage

A comprehensive review completes every category, recording "No issues found" where
a category produced nothing rather than leaving it blank.

| # | Category | Result |
|---|---|---|
| 1 | Correctness & logic bugs | 1 finding (Driver.FOCAS.Contracts-001) |
| 2 | OtOpcUa conventions | No issues found |
| 3 | Concurrency & thread safety | No issues found |
| 4 | Error handling & resilience | No issues found |
| 5 | Security | No issues found |
| 6 | Performance & resource management | No issues found |
| 7 | Design-document adherence | 1 finding (Driver.FOCAS.Contracts-002) |
| 8 | Code organization & conventions | No issues found |
| 9 | Testing coverage | No test project — findings recorded, deferred by task scope |
| 10 | Documentation & comments | 2 findings (Driver.FOCAS.Contracts-003, Driver.FOCAS.Contracts-004) |

## Findings

<!-- One ### entry per finding. IDs are <Module>-NNN, numbered sequentially within the module,
     never reused. Findings are never deleted — close them by changing Status and
     completing Resolution. -->

### Driver.FOCAS.Contracts-001

| Field | Value |
|---|---|
| Severity | Low |
| Category | Correctness & logic bugs |
| Location | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts/FocasDriverOptions.cs:144` |
| Status | Won't Fix |

**Description:** `FocasTagDefinition`'s positional parameter `Writable` defaults to `true`. The original review hypothesised that FOCAS is read-only by design (claiming `WireFocasClient.WriteAsync` always returns `BadNotWritable` and the `def.Writable` gate is dead code) and that the default should therefore be `false`. **That premise was wrong** — FOCAS supports PMC/data writes, the `def.Writable` gate is live, and six `Driver.FOCAS.Tests` write tests (`FocasPmcBitRmwTests`, `FocasReadWriteTests`) rely on `Writable` defaulting to `true`.

**Recommendation:** Leave the default at `true`. (The original recommendation to flip it to `false` is withdrawn.)

**Resolution:** Won't Fix (re-triaged 2026-06-19). The "FOCAS is read-only" premise was incorrect — the consuming `Driver.FOCAS.Tests` write suites failed when the default was flipped to `false`. The default `Writable = true` is intentional and correct; the change was reverted. The accompanying `<param>` doc was kept but corrected to describe the live write path. (Caught by the orchestrator's consuming-driver-test safety net, which the no-test-project Contracts build could not exercise.)

---

### Driver.FOCAS.Contracts-002

| Field | Value |
|---|---|
| Severity | Low |
| Category | Design-document adherence |
| Location | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts/FocasDriverOptions.cs:139-145` |
| Status | Resolved |

**Description:** `FocasTagDefinition` carries a `WriteIdempotent` field (default `false`) that the FOCAS driver never reads anywhere — neither in `DiscoverAsync`, `ReadAsync`, nor `WriteAsync`. `DiscoverAsync` always passes `WriteIdempotent: false` to `DriverAttributeInfo` (hardcoded), so the field has no runtime effect. `docs/drivers/FOCAS.md` does not mention `WriteIdempotent` in its configuration tables, making its purpose undiscoverable to operators.

**Recommendation:** Either (a) thread `FocasTagDefinition.WriteIdempotent` through to `DriverAttributeInfo` in `DiscoverAsync` so the field has runtime effect and matches the pattern of other drivers, or (b) remove it from the record and the `FocasDriverConfigDto` wire DTO. Option (a) is the safer fix and matches the design of Modbus and other drivers. This is deferred because the fix touches `FocasDriver.DiscoverAsync` outside this module and requires a driver-level test change.

**Resolution:** Fixed (option a). In `FocasDriver.DiscoverAsync` the hardcoded `WriteIdempotent: false` was replaced with `tag.WriteIdempotent` so each user-authored tag's per-tag value is now threaded through to `DriverAttributeInfo`. The `<param name="WriteIdempotent">` doc on `FocasTagDefinition` was updated to state it is now threaded through `DiscoverAsync` to `DriverAttributeInfo`. A new test `DiscoverAsync_surfaces_WriteIdempotent_from_tag_definition` was added to `FocasDriverMediumFindingsTests` asserting both the `true` and `false` cases surface correctly. The full `Driver.FOCAS.Tests` suite (including `FocasPmcBitRmwTests` and `FocasReadWriteTests` write tests) passes.

---

### Driver.FOCAS.Contracts-003

| Field | Value |
|---|---|
| Severity | Low |
| Category | Documentation & comments |
| Location | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts/FocasDriverOptions.cs:147-155` |
| Status | Resolved |

**Description:** `FocasProbeOptions` is the only class in this module without a class-level XML `<summary>` comment. All other options classes (`FocasDriverOptions`, `FocasFixedTreeOptions`, `FocasHandleRecycleOptions`, `FocasAlarmProjectionOptions`) have class-level summaries. This inconsistency causes IDE tooltips and XML-doc generators to produce a blank description for `FocasProbeOptions`.

**Recommendation:** Add a class-level `<summary>` consistent with the pattern of the other options types: `Controls periodic connectivity probing. One <c>cnc_rdcncstat</c> call per configured device per tick; transitions fire <c>OnHostStatusChanged</c>.`

**Resolution:** Fixed in the same commit as this review. Added XML `<summary>` to `FocasProbeOptions`. Verified by build (no test project).

---

### Driver.FOCAS.Contracts-004

| Field | Value |
|---|---|
| Severity | Low |
| Category | Documentation & comments |
| Location | `src/Drivers/ZB.MOM.WW.OtOpcUa.Driver.FOCAS.Contracts/FocasDriverOptions.cs:107-131` |
| Status | Resolved |

**Description:** `FocasDeviceOptions`'s class-level `<summary>` references `<paramref name="Series"/>` but there is no corresponding `<param name="Series">` documentation block. Only `PositionDecimalPlaces` has a `<param>` entry; `HostAddress`, `DeviceName`, and `Series` are all undocumented at the parameter level. This leaves the expected URI form of `HostAddress` (`focas://{ip}[:{port}]`) and the valid values of `Series` undiscoverable from the XML doc.

**Recommendation:** Add `<param>` entries for `HostAddress`, `DeviceName`, and `Series` documenting the expected URI form for `HostAddress` and referring to `FocasCncSeries.Unknown` as the permissive default for `Series`.

**Resolution:** Fixed in the same commit as this review. Added `<param>` doc entries for `HostAddress`, `DeviceName`, and `Series` to `FocasDeviceOptions`. Verified by build (no test project).
