Eternet.Mediator.Generator 3.1.56

Eternet.Mediator.Generator

Source generator package for production pipeline execution in Eternet.Mediator.

Installation

dotnet add package Eternet.Mediator.Generator

Use it as an analyzer/source-generator package in projects that generate mediator pipelines.

Runtime Ownership

Each assembly that declares [GenerateExecutePipeline<...>] must reference a pipeline generator so it can emit its own pipeline executors and StepsResults partials. In multi-assembly hosts, only one assembly should own the concrete mediator runtime (Mediator.Mediator, MediatorOptions, and AddMediator).

Prefer Eternet.Mediator.Pipeline.Generator for assemblies that need pipeline generation but should not own the runtime:

dotnet add package Eternet.Mediator.Pipeline.Generator

It emits pipeline executors, StepsResults, and pipeline registration extensions only.

The host/runtime owner can then include the pipeline-only assembly in TargetAssemblies:

services.AddMediator(options =>
{
    options.TargetAssemblies =
    [
        typeof(HostServiceRegistration).Assembly,
        typeof(FeatureFromPipelineOnlyAssembly).Assembly
    ];
});

TargetAssemblies controls handler discovery for the generated runtime. It does not generate pipeline code for other assemblies.

Step Execution Policies

[UseStepExecutionPolicy<TPolicy>] marks a step whose raw Handle(...) call is wrapped by a policy-managed input and outcome flow while the generated executor keeps owning retry, exception recovery, duration measurement, publication, and stateful resume.

Use it when the pipeline graph should keep the business step visible, but the app needs reusable per-step decisions such as skip rules, input construction, and mapping raw responses or failures to a domain outcome.

The step signature must expose exactly one domain input plus an optional CancellationToken:

[UseStepExecutionPolicy<RunExternalSyncPolicy>]
public sealed class RunExternalSyncAsync
{
    public Task<ExternalSyncResponse> Handle(
        ExternalSyncInput input,
        CancellationToken cancellationToken)
    {
        return client.RunAsync(input, cancellationToken);
    }
}

The policy implements the exact closed contract:

public sealed class RunExternalSyncPolicy
    : IStepExecutionPolicy<
        RunSynchronization.Request,
        ExternalSyncInput,
        ExternalSyncResponse,
        ScheduledSynchronizationOutcome>
{
    public ValueTask<StepExecutionInput<ExternalSyncInput>> BuildInputAsync(
        RunSynchronization.Request request,
        StepExecutionPolicyContext context,
        CancellationToken cancellationToken)
    {
        return request.Options.Enabled
            ? ValueTask.FromResult(StepExecutionInput<ExternalSyncInput>.Execute(new(request.ExecutionId)))
            : ValueTask.FromResult(StepExecutionInput<ExternalSyncInput>.Skip("External sync is disabled."));
    }

    public ValueTask<ScheduledSynchronizationOutcome> MapAsync(
        RunSynchronization.Request request,
        StepExecutionResult<ExternalSyncResponse> result,
        StepExecutionPolicyContext context,
        CancellationToken cancellationToken)
    {
        return ValueTask.FromResult(ScheduledSynchronizationOutcome.From(result));
    }
}

For policy-managed steps, StepsResults publishes the mapped TStepOutcome, not the raw TStepResponse. Stateful pipelines persist the mapped outcome and reuse it on resume when ReExecutionPolicy = ReuseIfAvailable.

Diagnostics:

• EM105: unsupported policy-managed step signature.
• EM106: policy type does not implement the exact closed IStepExecutionPolicy<...> contract.

Full consumer guide: ../doc/StepExecutionPolicies.md.

Breaking Changes in 3.0.0

Eternet.Mediator.Generator 3.0.0 emits code against the new generated runtime facade.

• Generated executors no longer declare or pass ScopedStates.
• Generated code uses an assembly-local generated runtime helper backed by GeneratedBindingRuntime.
• request.StepsResults is the supported developer-facing result model.
• Applications or tests that still depend on public ScopedStates-based generated output must stay on 2.x until migrated.

Migration guide: ../docs/scoped-states-breaking-change-v3.md