Introduce FaultGenerator and OutcomeGenerator<T>

src/Polly.Core/PublicAPI.Unshipped.txt

@@ -20,6 +20,11 @@ Polly.Simmy.EnabledGeneratorArguments
 Polly.Simmy.EnabledGeneratorArguments.Context.get -> Polly.ResilienceContext!
 Polly.Simmy.EnabledGeneratorArguments.EnabledGeneratorArguments() -> void
 Polly.Simmy.EnabledGeneratorArguments.EnabledGeneratorArguments(Polly.ResilienceContext! context) -> void
+Polly.Simmy.Fault.FaultGenerator
+Polly.Simmy.Fault.FaultGenerator.AddException(System.Func<Polly.ResilienceContext!, System.Exception!>! generator, int weight = 100) -> Polly.Simmy.Fault.FaultGenerator!
+Polly.Simmy.Fault.FaultGenerator.AddException(System.Func<System.Exception!>! generator, int weight = 100) -> Polly.Simmy.Fault.FaultGenerator!
+Polly.Simmy.Fault.FaultGenerator.AddException<TException>(int weight = 100) -> Polly.Simmy.Fault.FaultGenerator!
+Polly.Simmy.Fault.FaultGenerator.FaultGenerator() -> void
 Polly.Simmy.Fault.FaultGeneratorArguments
 Polly.Simmy.Fault.FaultGeneratorArguments.Context.get -> Polly.ResilienceContext!
 Polly.Simmy.Fault.FaultGeneratorArguments.FaultGeneratorArguments() -> void
@@ -84,12 +89,17 @@ Polly.Simmy.Outcomes.OnOutcomeInjectedArguments<TResult>.Context.get -> Polly.Re
 Polly.Simmy.Outcomes.OnOutcomeInjectedArguments<TResult>.OnOutcomeInjectedArguments() -> void
 Polly.Simmy.Outcomes.OnOutcomeInjectedArguments<TResult>.OnOutcomeInjectedArguments(Polly.ResilienceContext! context, Polly.Outcome<TResult> outcome) -> void
 Polly.Simmy.Outcomes.OnOutcomeInjectedArguments<TResult>.Outcome.get -> Polly.Outcome<TResult>
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.AddException(System.Func<Polly.ResilienceContext!, System.Exception!>! generator, int weight = 100) -> Polly.Simmy.Outcomes.OutcomeGenerator<TResult>!
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.AddException(System.Func<System.Exception!>! generator, int weight = 100) -> Polly.Simmy.Outcomes.OutcomeGenerator<TResult>!
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.AddException<TException>(int weight = 100) -> Polly.Simmy.Outcomes.OutcomeGenerator<TResult>!
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.AddResult(System.Func<Polly.ResilienceContext!, TResult>! generator, int weight = 100) -> Polly.Simmy.Outcomes.OutcomeGenerator<TResult>!
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.AddResult(System.Func<TResult>! generator, int weight = 100) -> Polly.Simmy.Outcomes.OutcomeGenerator<TResult>!
+Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.OutcomeGenerator() -> void
 Polly.Simmy.Outcomes.OutcomeGeneratorArguments
 Polly.Simmy.Outcomes.OutcomeGeneratorArguments.Context.get -> Polly.ResilienceContext!
 Polly.Simmy.Outcomes.OutcomeGeneratorArguments.OutcomeGeneratorArguments() -> void
 Polly.Simmy.Outcomes.OutcomeGeneratorArguments.OutcomeGeneratorArguments(Polly.ResilienceContext! context) -> void
-Polly.Simmy.Outcomes.OutcomeStrategyOptions
-Polly.Simmy.Outcomes.OutcomeStrategyOptions.OutcomeStrategyOptions() -> void
 Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>
 Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>.OnOutcomeInjected.get -> System.Func<Polly.Simmy.Outcomes.OnOutcomeInjectedArguments<TResult>, System.Threading.Tasks.ValueTask>?
 Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>.OnOutcomeInjected.set -> void
@@ -98,9 +108,11 @@ Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>.OutcomeGenerator.set -> voi
 Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>.OutcomeStrategyOptions() -> void
 static Polly.Simmy.BehaviorPipelineBuilderExtensions.AddChaosBehavior<TBuilder>(this TBuilder! builder, double injectionRate, System.Func<System.Threading.Tasks.ValueTask>! behavior) -> TBuilder!
 static Polly.Simmy.BehaviorPipelineBuilderExtensions.AddChaosBehavior<TBuilder>(this TBuilder! builder, Polly.Simmy.Behavior.BehaviorStrategyOptions! options) -> TBuilder!
+static Polly.Simmy.Fault.FaultGenerator.implicit operator System.Func<Polly.Simmy.Fault.FaultGeneratorArguments, System.Threading.Tasks.ValueTask<System.Exception?>>!(Polly.Simmy.Fault.FaultGenerator! generator) -> System.Func<Polly.Simmy.Fault.FaultGeneratorArguments, System.Threading.Tasks.ValueTask<System.Exception?>>!
 static Polly.Simmy.FaultPipelineBuilderExtensions.AddChaosFault<TBuilder>(this TBuilder! builder, double injectionRate, System.Func<System.Exception?>! faultGenerator) -> TBuilder!
 static Polly.Simmy.FaultPipelineBuilderExtensions.AddChaosFault<TBuilder>(this TBuilder! builder, Polly.Simmy.Fault.FaultStrategyOptions! options) -> TBuilder!
 static Polly.Simmy.LatencyPipelineBuilderExtensions.AddChaosLatency<TBuilder>(this TBuilder! builder, double injectionRate, System.TimeSpan latency) -> TBuilder!
 static Polly.Simmy.LatencyPipelineBuilderExtensions.AddChaosLatency<TBuilder>(this TBuilder! builder, Polly.Simmy.Latency.LatencyStrategyOptions! options) -> TBuilder!
 static Polly.Simmy.OutcomePipelineBuilderExtensions.AddChaosResult<TResult>(this Polly.ResiliencePipelineBuilder<TResult>! builder, double injectionRate, System.Func<TResult?>! resultGenerator) -> Polly.ResiliencePipelineBuilder<TResult>!
 static Polly.Simmy.OutcomePipelineBuilderExtensions.AddChaosResult<TResult>(this Polly.ResiliencePipelineBuilder<TResult>! builder, Polly.Simmy.Outcomes.OutcomeStrategyOptions<TResult>! options) -> Polly.ResiliencePipelineBuilder<TResult>!
+static Polly.Simmy.Outcomes.OutcomeGenerator<TResult>.implicit operator System.Func<Polly.Simmy.Outcomes.OutcomeGeneratorArguments, System.Threading.Tasks.ValueTask<Polly.Outcome<TResult>?>>!(Polly.Simmy.Outcomes.OutcomeGenerator<TResult>! generator) -> System.Func<Polly.Simmy.Outcomes.OutcomeGeneratorArguments, System.Threading.Tasks.ValueTask<Polly.Outcome<TResult>?>>!

src/Polly.Core/Simmy/Fault/FaultGenerator.cs

@@ -0,0 +1,84 @@
+using System.ComponentModel;
+using Polly.Simmy.Utils;
+
+namespace Polly.Simmy.Fault;
+
+#pragma warning disable CA2225 // Operator overloads have named alternates
+#pragma warning disable RS0026 // Do not add multiple public overloads with optional parameters
+
+/// <summary>
+/// A generator for creating faults (exceptions) using registered delegate functions.
+/// </summary>
+/// <remarks>
+/// An instance of this class can be assigned to the <see cref="FaultStrategyOptions.FaultGenerator"/> property.
+/// </remarks>
+public sealed class FaultGenerator
+{
+    private const int DefaultWeight = 100;
+
+    private readonly GeneratorHelper<VoidResult> _helper;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="FaultGenerator"/> class.
+    /// </summary>
+    public FaultGenerator()
+        => _helper = new GeneratorHelper<VoidResult>(RandomUtil.Instance.Next);
+
+    /// <summary>
+    /// Registers an exception generator delegate.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the exception.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="FaultGenerator"/>.</returns>
+    public FaultGenerator AddException(Func<Exception> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(_ => Outcome.FromException<VoidResult>(generator()), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers an exception generator delegate that accepts a <see cref="ResilienceContext"/>.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the exception, accepting a <see cref="ResilienceContext"/>.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="FaultGenerator"/>.</returns>
+    public FaultGenerator AddException(Func<ResilienceContext, Exception> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(context => Outcome.FromException<VoidResult>(generator(context)), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers an exception generator for a specific exception type, using the default constructor of that exception.
+    /// </summary>
+    /// <typeparam name="TException">The type of the exception to generate.</typeparam>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="FaultGenerator"/>.</returns>
+    public FaultGenerator AddException<TException>(int weight = DefaultWeight)
+        where TException : Exception, new()
+    {
+        _helper.AddOutcome(_ => Outcome.FromException<VoidResult>(new TException()), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Provides an implicit conversion from <see cref="FaultGenerator"/> to a delegate compatible with <see cref="FaultStrategyOptions.FaultGenerator"/>.
+    /// </summary>
+    /// <param name="generator">The instance of <see cref="FaultGenerator"/>.</param>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public static implicit operator Func<FaultGeneratorArguments, ValueTask<Exception?>>(FaultGenerator generator)
+    {
+        Guard.NotNull(generator);
+
+        var generatorDelegate = generator._helper.CreateGenerator();
+
+        return args => new ValueTask<Exception?>(generatorDelegate(args.Context)!.Value.Exception);
+    }
+}

src/Polly.Core/Simmy/Outcomes/OutcomeGenerator.cs

@@ -0,0 +1,120 @@
+using System.ComponentModel;
+using Polly.Simmy.Utils;
+
+namespace Polly.Simmy.Outcomes;
+
+#pragma warning disable CA2225 // Operator overloads have named alternates
+#pragma warning disable RS0026 // Do not add multiple public overloads with optional parameters
+
+/// <summary>
+/// Generator that produces faults such as exceptions or results.
+/// </summary>
+/// <typeparam name="TResult">The type of the result.</typeparam>
+/// <remarks>
+/// An instance of this class is assignable to <see cref="OutcomeStrategyOptions{TResult}.OutcomeGenerator"/>.
+/// </remarks>
+public sealed class OutcomeGenerator<TResult>
+{
+    private const int DefaultWeight = 100;
+    private readonly GeneratorHelper<TResult> _helper;
+
+    /// <summary>
+    /// Initializes a new instance of the <see cref="OutcomeGenerator{TResult}"/> class.
+    /// </summary>
+    public OutcomeGenerator()
+        : this(RandomUtil.Instance.Next)
+    {
+    }
+
+    internal OutcomeGenerator(Func<int, int> weightGenerator)
+        => _helper = new GeneratorHelper<TResult>(weightGenerator);
+
+    /// <summary>
+    /// Registers an exception generator delegate.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the exception.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="OutcomeGenerator{TResult}"/>.</returns>
+    public OutcomeGenerator<TResult> AddException(Func<Exception> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(_ => Outcome.FromException<TResult>(generator()), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers an exception generator delegate that accepts a <see cref="ResilienceContext"/>.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the exception, accepting a <see cref="ResilienceContext"/>.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="OutcomeGenerator{TResult}"/>.</returns>
+    public OutcomeGenerator<TResult> AddException(Func<ResilienceContext, Exception> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(context => Outcome.FromException<TResult>(generator(context)), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers an exception generator for a specific exception type, using the default constructor of that exception.
+    /// </summary>
+    /// <typeparam name="TException">The type of the exception to generate.</typeparam>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="OutcomeGenerator{TResult}"/>.</returns>
+    public OutcomeGenerator<TResult> AddException<TException>(int weight = DefaultWeight)
+        where TException : Exception, new()
+    {
+        _helper.AddOutcome(_ => Outcome.FromException<TResult>(new TException()), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers a result generator.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the result.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="OutcomeGenerator{TResult}"/>.</returns>
+    public OutcomeGenerator<TResult> AddResult(Func<TResult> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(_ => Outcome.FromResult(generator()), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Registers a result generator.
+    /// </summary>
+    /// <param name="generator">The delegate that generates the result, accepting a <see cref="ResilienceContext"/>.</param>
+    /// <param name="weight">The weight assigned to this generator. Defaults to <c>100</c>.</param>
+    /// <returns>The current instance of <see cref="OutcomeGenerator{TResult}"/>.</returns>
+    public OutcomeGenerator<TResult> AddResult(Func<ResilienceContext, TResult> generator, int weight = DefaultWeight)
+    {
+        Guard.NotNull(generator);
+
+        _helper.AddOutcome(context => Outcome.FromResult(generator(context)), weight);
+
+        return this;
+    }
+
+    /// <summary>
+    /// Implicit conversion to <see cref="OutcomeStrategyOptions{TResult}.OutcomeGenerator"/>.
+    /// </summary>
+    /// <param name="generator">The generator instance.</param>
+    [EditorBrowsable(EditorBrowsableState.Never)]
+    public static implicit operator Func<OutcomeGeneratorArguments, ValueTask<Outcome<TResult>?>>(OutcomeGenerator<TResult> generator)
+    {
+        Guard.NotNull(generator);
+
+        var generatorDelegate = generator._helper.CreateGenerator();
+
+        return args => new ValueTask<Outcome<TResult>?>(generatorDelegate(args.Context));
+    }
+}
+

src/Polly.Core/Simmy/Outcomes/OutcomeStrategyOptions.cs

@@ -1,6 +1,24 @@
-namespace Polly.Simmy.Outcomes;
+using System.ComponentModel.DataAnnotations;
 
-/// <inheritdoc/>
-public class OutcomeStrategyOptions : OutcomeStrategyOptions<object>
+namespace Polly.Simmy.Outcomes;
+
+/// <summary>
+/// Represents the options for the Outcome chaos strategy.
+/// </summary>
+/// <typeparam name="TResult">The type of the outcome that was injected.</typeparam>
+public class OutcomeStrategyOptions<TResult> : MonkeyStrategyOptions
 {
+    /// <summary>
+    /// Gets or sets the delegate that's invoked when the outcome is injected.
+    /// </summary>
+    /// <remarks>
+    /// Defaults to <see langword="null"/>.
+    /// </remarks>
+    public Func<OnOutcomeInjectedArguments<TResult>, ValueTask>? OnOutcomeInjected { get; set; }
+
+    /// <summary>
+    /// Gets or sets the outcome generator to be injected for a given execution.
+    /// </summary>
+    [Required]
+    public Func<OutcomeGeneratorArguments, ValueTask<Outcome<TResult>?>> OutcomeGenerator { get; set; } = default!;
 }

src/Polly.Core/Simmy/Utils/GeneratorHelper.cs

@@ -0,0 +1,52 @@
+namespace Polly.Simmy.Utils;
+
+internal sealed class GeneratorHelper<TResult>
+{
+    private readonly Func<int, int> _weightGenerator;
+
+    private readonly List<int> _weights = [];
+    private readonly List<Func<ResilienceContext, Outcome<TResult>>> _factories = [];
+    private int _totalWeight;
+
+    public GeneratorHelper(Func<int, int> weightGenerator) => _weightGenerator = weightGenerator;
+
+    public void AddOutcome(Func<ResilienceContext, Outcome<TResult>> generator, int weight)
+    {
+        Guard.NotNull(generator);
+
+        _totalWeight += weight;
+        _factories.Add(generator);
+        _weights.Add(weight);
+    }
+
+    internal Func<ResilienceContext, Outcome<TResult>?> CreateGenerator()
+    {
+        if (_factories.Count == 0)
+        {
+            return _ => null;
+        }
+
+        var totalWeight = _totalWeight;
+        var factories = _factories.ToArray();
+        var weights = _weights.ToArray();
+        var generator = _weightGenerator;
+
+        return context =>
+        {
+            var generatedWeight = generator(totalWeight);
+            var weight = 0;
+
+            for (var i = 0; i < factories.Length; i++)
+            {
+                weight += weights[i];
+                if (generatedWeight < weight)
+                {
+                    return factories[i](context);
+                }
+            }
+
+            return null;
+        };
+    }
+}
+

src/Polly.Core/Utils/RandomUtil.cs

@@ -13,4 +13,6 @@ internal sealed class RandomUtil
     public RandomUtil(int? seed) => _random = new ThreadLocal<Random>(() => seed == null ? new Random() : new Random(seed.Value));
 
     public double NextDouble() => _random.Value!.NextDouble();
+
+    public int Next(int maxValue) => _random.Value!.Next(maxValue);
 }