Requirements

Requirements fail a pipeline before module execution when an environment prerequisite is not satisfied. Register built-in requirements through the Require factory:

builder.AddRequirement(Require.Windows());
builder.AddRequirement(Require.EnvironmentVariable("NUGET_API_KEY"));
builder.AddRequirement(Require.Ci("Publishing can only run in CI"));

The platform shortcuts are Require.Windows(), Require.Linux(), Require.MacOS(), and Require.WindowsAdmin(). Use Require.Platform(...) for another OSPlatform value.

For custom asynchronous checks, implement IPipelineRequirement or derive from PipelineRequirement. Evaluation receives the pipeline cancellation token:

public sealed class HasDotNetSdkRequirement : PipelineRequirement
{
    public override async Task<RequirementDecision> EvaluateAsync(
        IPipelineContext context,
        CancellationToken cancellationToken)
    {
        var result = await context.Shell.RunAsync(
            "dotnet",
            ["--version"],
            cancellationToken: cancellationToken);

        return result.ExitCode == 0
            ? RequirementDecision.Passed
            : RequirementDecision.Failed(".NET SDK is not installed");
    }
}

For synchronous checks, return a completed task from EvaluateAsync:

public sealed class Is64BitRequirement : PipelineRequirement
{
    public override Task<RequirementDecision> EvaluateAsync(
        IPipelineContext context,
        CancellationToken cancellationToken)
        => Task.FromResult(
            Environment.Is64BitProcess
                ? RequirementDecision.Passed
                : RequirementDecision.Failed("A 64-bit process is required"));
}

RequirementDecision.IsSatisfied reports the outcome. Construct decisions with Passed or Failed(reason); a bool can also convert implicitly. A bare string does not imply failure.

Requirements and run conditions receive IPipelineContext, giving them the same shared capability surface as global hooks. Use IModuleContext only inside modules.