Inbox Accept Rules

Header

• ID: analyzers.inbox-result-command-guard
• Diagnostic: LB1004 (Error)
• Maturity: GA
• Summary: Reports result-bearing commands passed to inbox accept APIs because inbox persistence discards handler return values.

Trigger Conditions

LB1004 reports when:

• Invocation target is AcceptAsync or AcceptBatchAsync.
• Receiver type is IInbox, ITransactionalInbox, or a type implementing either.
• Message type implements ICommand<TResult>.

Batch detection includes:

• Implicit arrays, explicit arrays, and collection expressions.
• InboxAcceptItem<T> and InboxAcceptItem.From(...) item shapes.
• Explicit generic calls such as AcceptAsync<CreateUserCommand>(...).

Bad Example

using System.Threading;
using System.Threading.Tasks;
using LiteBus.Commands.Abstractions;
using LiteBus.Inbox.Abstractions;

public sealed record CreateUserCommand(string Name) : ICommand<int>;

public sealed class UserService
{
    public Task ScheduleAsync(IInbox inbox, CreateUserCommand command, CancellationToken cancellationToken)
        => inbox.AcceptAsync(command, cancellationToken: cancellationToken);
}

Expected diagnostic:

• LB1004 on AcceptAsync(...).

Good Example

using System.Threading;
using System.Threading.Tasks;
using LiteBus.Commands.Abstractions;
using LiteBus.Inbox.Abstractions;

public sealed record ProcessPaymentCommand(int PaymentId) : ICommand;

public sealed class PaymentService
{
    public Task ScheduleAsync(IInbox inbox, ProcessPaymentCommand command, CancellationToken cancellationToken)
        => inbox.AcceptAsync(command, cancellationToken: cancellationToken);
}

Suppression Guidance

• Do not suppress for production code paths, convert stored commands to result-less ICommand.
• If a result is required immediately, send with ICommandMediator instead of storing through inbox.
• Keep any suppression local to migrations where old message contracts cannot be changed yet.

Test Coverage

Source: tests/LiteBus.Analyzers.UnitTests/CommandWithResultScheduledToInboxAnalyzerTests.cs

Untested in this suite:

• AcceptBatchAsync fixture coverage for mixed item sources and collection expressions.