LS2004: Command Handler Writes Through a Document Session

LS2004 is a compiler check that reports a command handler, the type that runs the state change, writing through a document session or database context instead of a repository, which bypasses the boundary that guards the business record. This page states what the rule reports, where the warning sits, and how to reach stored data through a Domain repository.

Reference#

What the rule enforces#

LS2004 enforces Stage aggregate writes through repositories (litespec/backend/dotnet/persistence#stage-aggregate-writes-through-repositories). It runs in Application and Infrastructure. Its category is LiteSpec.Layers. It reports a warning and is enabled by default, as the Analyzers overview describes.

What the rule reports#

The rule reports a command handler, recognized as in LS2002: Command Handler Dispatches Another Command, that holds IDocumentSession, DbContext, or a DbContext subclass in a field, property, constructor parameter, or local, or that calls a member through such a receiver. In a declaration the diagnostic sits on the type. In a call it sits on the invoked member name.

Failing example#

internal sealed class PlaceOrderCommandHandler
{
    private readonly IDocumentSession _session = null!;
}

Passing example#

internal sealed class PlaceOrderCommandHandler(IOrderRepository orders)
{
    public void Handle(PlaceOrderCommand command) => orders.Store(command);
}

How to fix#

Reach persistence only through a Domain repository that the handler takes as a constructor parameter.

Notes#

What the rule ignores#

The rule does not report handlers that reach persistence only through a Domain repository, or query handlers. It does not run in Domain, Application.Abstractions, or WebApi.