Module History

What is it?

If a repository has been set up, the pipeline attempts to save successful module results and failure results whose failures are ignored (FailureIgnored). An ignored failure still contains an exception and has no successful value.

This can be used later on if you want to re-run the pipeline but skip certain categories or modules.

If a module is skipped and a historical result is available, the pipeline restores that result with status RestoredFromHistory. Restoration changes the status, not the result variant: a stored failure remains a failure, and reading its .Value throws. Dependent modules must inspect the outcome before consuming the value; the restored status alone does not prove success.

For example, when a dependency returns ModuleResult<string>, handle each variant:

switch (result)
{
    case ModuleResult<string>.Success { Value: var value }:
        // Consume value.
        break;
    case ModuleResult<string>.Failure { Exception: var exception }:
        // Handle the stored failure.
        break;
    case ModuleResult<string>.Skipped { Decision: var decision }:
        // Handle the skipped outcome.
        break;
}

Alternatively, use TryGetValue(out var value) to check for a successful value without throwing. ValueOrDefault also avoids throwing, but cannot distinguish a failure from a successful default value.

It's recommended to store and retrieve results using the Git commit SHA, as then you'll only be using the results from that previous commit's run. And other commits remain unaffected. You have access to a context object that gives you access to things like the git information.

Example Repository Class using Azure Blobs

var builder = Pipeline.CreateBuilder(args);

builder
    .AddModule<Module1>()
    .AddModule<Module2>()
    .AddModule<Module3>();

builder.AddResultsRepository<MyModuleRepository>();

await builder.RunAsync();

Result history resolves type-erased module results at runtime and is not supported for trimmed or Native AOT applications. AddResultsRepository<TRepository>() emits the corresponding trim and dynamic-code warnings.

The example below keys each result by commit SHA, so it requires a Git checkout. Outside one, GetRequiredInfoAsync throws, so the example neither stores nor restores history there. To keep history outside Git, call GetInfoAsync instead and choose a fallback key when it returns null.

public class MyModuleRepository : IModuleResultRepository
{
    private readonly BlobContainerClient _blobContainerClient;

    public MyModuleRepository(BlobContainerClient blobContainerClient)
    {
        _blobContainerClient = blobContainerClient;
    }
    
    public async Task SaveResultAsync<T>(
        Module<T> module,
        ModuleResult<T> moduleResult,
        IPipelineContext pipelineContext,
        CancellationToken cancellationToken = default)
    {
        var repositoryInfo = await pipelineContext.Tools.Git.Information.GetRequiredInfoAsync(cancellationToken);
        var commit = repositoryInfo.LastCommitSha;
        await _blobContainerClient.UploadBlobAsync(
            module.GetType().FullName + commit,
            new BinaryData(JsonSerializer.Serialize(moduleResult)),
            cancellationToken);
    }

    public async Task<ModuleResult<T>?> GetResultAsync<T>(
        Module<T> module,
        IPipelineContext pipelineContext,
        CancellationToken cancellationToken = default)
    {
        var repositoryInfo = await pipelineContext.Tools.Git.Information.GetRequiredInfoAsync(cancellationToken);
        var commit = repositoryInfo.LastCommitSha;

        var blobContent = await _blobContainerClient
            .GetBlobClient(module.GetType().FullName + commit)
            .DownloadContentAsync(cancellationToken);

        return JsonSerializer.Deserialize<ModuleResult<T>>(blobContent.Value.Content.ToString());
    }
}

Behavior

• Restored results have the RestoredFromHistory status and retain their success, failure, or skipped variant. Dependent modules can inspect them, but only a success variant has a value.
• Repository failures are best-effort: exceptions from SaveResultAsync and GetResultAsync are logged, and the module runs (or is skipped) as if no result was stored.
• IsEnabled defaults to true; return false to switch the repository off without removing it.
• Result history is separate from module caching, which restores results by input fingerprint, and from the time estimator, which stores durations.