---
title: Chronicle code analysis
editUrl: https://github.com/Cratis/Arc.TypeScript/edit/main/Documentation/chronicle/code-analysis.md
description: Arc on .NET's Chronicle diagnostics mapped to TypeScript lint rules, runtime checks, and inapplicable C# patterns.
---


As of .NET v22.23.0, Arc shipped ten Chronicle analyzers (`ARCCHR0001`–`ARCCHR0010`); this mapping covers that set.
Five have bounded TypeScript ESLint analogs in `@cratis/eslint-plugin-arc-core`.
Configure the plugin as described in [Code analysis](/arc/backend/typescript/code-analysis/).
Both presets enable `arcchr0003`, `arcchr0007`, and `arcchr0009`.
`arcchr0006` and `arcchr0010` need type information and are enabled by `recommended-type-checked`.
ESLint reports enabled rules as errors, including analogs of .NET warnings.

## ARCCHR mapping

| .NET diagnostic | .NET default | TypeScript status |
| --- | --- | --- |
| ARCCHR0001, aggregate handler signature | Error | N/A |
| ARCCHR0002, ambiguous command identity | Warning | N/A / runtime |
| [ARCCHR0003](/arc/backend/typescript/code-analysis/arcchr0003/), reactor reaches default log | Warning | ESLint analog |
| ARCCHR0004, redundant `[EventType]` id | Warning | N/A |
| ARCCHR0005, Chronicle used but not configured | Warning | Partly caught at runtime |
| [ARCCHR0006](/arc/backend/typescript/code-analysis/arcchr0006/), reactor returns a command without a replay decision | Warning | Type-checked ESLint analog |
| [ARCCHR0007](/arc/backend/typescript/code-analysis/arcchr0007/), command injects event log | Warning | ESLint analog |
| ARCCHR0008, data annotations `[Key]` | Warning | N/A |
| [ARCCHR0009](/arc/backend/typescript/code-analysis/arcchr0009/), secret-looking command property | Warning | ESLint analog for names not masked at runtime |
| [ARCCHR0010](/arc/backend/typescript/code-analysis/arcchr0010/), raw GUID response | Warning | Type-checked ESLint analog |

- **ARCCHR0001:** `this.on(EventClass, handler)` registers a typed callback; duplicate handlers throw.
  No `On` method-signature convention exists.
- **ARCCHR0002:** `getEventSourceId()`, `getKey()`, or one `@key()` determines the key.
  A second `@key()` throws when the class is defined.
- **ARCCHR0003:** The rule finds direct `eventLog.append` or `appendMany` calls through a `this` field
  initialized from `this.client.getEventStore` or `this.runtime.getStore`. It cannot prove the field's
  store belongs to the reactor; it ignores fields initialized from another client. Return events instead.
- **ARCCHR0004:** An explicit TypeScript SDK ID equal to the class name stabilizes persisted type identity
  across minification or renaming. Removing it changes guarantees.
- **ARCCHR0005:** `commandReadModel(Type)` without an owner fails `build()`.
  A returned event without `withChronicle` becomes an ordinary response and is not caught.
  A per-file ESLint rule cannot prove registration in a separate host module.
- **ARCCHR0006:** TypeScript reactors return Arc commands rather than calling .NET's
  `ICommandPipeline.Execute`. The type-checked rule follows same-class helper calls back to live
  handlers and warns when none has a replay decision. Class- or handler-level `@onceOnly()` and an
  `@replay()` handler for the same event silence it. Dispatch matches the camel-cased event class
  name, not the parameter annotation. See [the rule's bounds](/arc/backend/typescript/code-analysis/arcchr0006/).
- **ARCCHR0007:** The rule finds direct `eventLog.append` or `appendMany` calls from a command's
  `handle()` or `provide()` through an artifact store or a `@inject(ChronicleReadModels | ChronicleRuntime)`
  parameter, including local and inline `getStore()` calls. Indirect appends remain a review concern.
- **ARCCHR0008:** TypeScript has only Arc's `@key()`; there is no competing data-annotations decorator.
- **ARCCHR0009:** Arc withholds names containing `password`, `secret`, `token`, `credential`, or `apiKey`,
  and fields marked `@notAudited()` or `@pii()`. The rule checks the remaining .NET secret words,
  including Passphrase, PrivateKey, and AuthorizationHeader, without falsely claiming masked names
  are written to causation.
- **ARCCHR0010:** A keyless command returning `tuple(Guid.create(), new DecoratedEvent())` returns
  an ordinary response instead of selecting the event source. The type-checked rule also recognizes
  Guid variables and `Guid.parse(...)`; it does not infer plain strings, indirect event factories,
  inherited event-type decorators, or other tuple shapes.

As of .NET v22.23.0, there was no ARCCHR analyzer for nullable event properties or past-tense event names;
this mapping does not add either rule.

## What to check in review

- Appends through helper methods or stores not held directly by a command or reactor can bypass the return-value pipeline.
- Commands executed manually inside a reactor (for example through an Arc server) are not detected.
  They still need a replay decision; `@onceOnly()` skips replay but does not prevent failed-partition
  re-delivery. See [Returning commands from a reactor](/arc/backend/typescript/chronicle/reactors/command-side-effects/#when-a-command-fails).
- An app that returns events must install `withChronicle`; check the host, not just the artifact file.
- A tuple carrying an ordinary string instead of `eventSourceIdResponse(id)` does not select an event source;
  see [Resolving the event source ID](/arc/backend/typescript/chronicle/resolving-event-source-id/#return-the-id-to-the-caller).

## Related

- [Code analysis](/arc/backend/typescript/code-analysis/)
- [Chronicle](/arc/backend/typescript/chronicle/)