ARCCHR0021: Use event source definition routing

Rule

Legacy EventSourceType / EventStreamType strings on EventForEventSourceId spell out a declared event source stream. The route still works, but Arc appends by those strings rather than through the definition: EventContext.EventSource and the selected definition’s concurrency dimensions are lost.

When the strings equal the enclosing command’s [EventSource<T>(stream)] route, the message also says the override is redundant. A different declared route remains supported; this suggestion is about retaining the definition, not making every event follow the command.

Severity

Info

Example

This wrapper names the declared Account.Transactions stream using legacy strings:

using Cratis.Chronicle.Events;
using Cratis.Chronicle.EventSequences;
using Cratis.Chronicle.EventSources;

[EventSource]
[EventStream("Transactions")]
public class AccountEventSource : IEventSource;

public static class AccountEvents
{
    public static EventForEventSourceId Route(EventSourceId id, object fact) =>
        new(id, fact)
        {
            EventSourceType = "Account",
            EventStreamType = "Transactions" // ARCCHR0021
        };
}

Replace the initializer’s routing assignments with:

EventSource = typeof(AccountEventSource),
EventStream = "Transactions"

This initializer excerpt uses the definition above. It preserves the source and stream names while retaining the definition for the append.

Quick fix

Use event source definition routing replaces the legacy assignments with EventSource = typeof(Definition) and EventStream = "stream". It keeps unrelated wrapper values, including stream id, subject, occurrence time, and tags. Fix All is supported.

Review concurrency before applying the fix: the definition’s policy now participates in ordinary derived guards. Explicit command concurrency: true choices still win, and returned exact scopes still replace derived scopes. The fix does not remove command attributes or rewrite legacy routes automatically at runtime.

Boundaries

The analyzer recognizes literal strings, including routing-concept constructors around literals, on object-creation and with initializers. Legacy source-name lookup covers definitions in the same compilation only; ambiguous names, unknown names, undeclared streams, computed values, sentinels, and unknown inherited routing are left alone. If only a stream is set, the enclosing [Command]’s [EventSource<T>] supplies the source. Typed routing and IEventRoutes / route.Route(...) need no migration diagnostic.