CHR0029: Redundant .Set(...).To(...) with matching property names

Rule Description

AutoMap is enabled by default and maps event properties to identically named read model properties. A .Set(x => x.P).To(e => e.P) mapping where the source and target property names are the same duplicates what AutoMap already does. Remove the redundant mapping and rely on AutoMap.

Severity

Warning

Example

C#

using Cratis.Chronicle.Events;
using Cratis.Chronicle.Projections;

public record Chr0029Customer(string Name);

[EventType]
public record Chr0029CustomerRegistered(string Name);

public class Chr0029CustomerProjection : IProjectionFor<Chr0029Customer>
{
    public void Define(IProjectionBuilderFor<Chr0029Customer> builder) =>
        builder.From<Chr0029CustomerRegistered>(customer => customer
            // Warning CHR0029: '.Set(x => x.Name).To(e => e.Name)' is redundant — AutoMap already maps
            // identically named properties. Remove the mapping.
            .Set(x => x.Name).To(e => e.Name));
}

Why This Rule Exists

.Set(...).To(...) is for the cases AutoMap cannot infer — a read model property whose name differs from the event property that feeds it. When both lambdas name the same property, the mapping restates the default AutoMap already applies, so the line carries no information and only obscures the mappings that do matter.

The analyzer is deliberately conservative: it fires only when both lambdas are simple param => param.Member member accesses and the two names are identical. A mapping that renames (Set(x => x.DisplayName).To(e => e.Name)) or transforms the value is doing real work and is left alone.

Related Rules

• CHR0028 — an explicit .AutoMap() call, which is redundant for the same reason.
• Model-bound projections — the full reference.