added Tap extensions generator

Railway.SourceGenerator/ResultMethodGenerator.cs

@@ -16,6 +16,7 @@ public class ResultMethodGenerator : IIncrementalGenerator
         new ResultMatchExecutor(),
         new ResultMapExecutor(),
         new ResultBindExecutor(),
+        new ResultTapExecutor(),
     };
 
     public void Initialize(IncrementalGeneratorInitializationContext context)

Railway.SourceGenerator/ResultTapExecutor.cs

@@ -0,0 +1,112 @@
+using System.Collections.Immutable;
+using System.Linq;
+using System.Text;
+using Microsoft.CodeAnalysis;
+
+namespace Just.Railway.SourceGen;
+
+internal sealed class ResultTapExecutor : ResultExtensionsExecutor
+{
+    protected override string ExtensionType => "Tap";
+
+    protected override void GenerateMethodsForArgCount(StringBuilder sb, int argCount)
+    {
+        var templateArgNames = Enumerable.Range(1, argCount)
+            .Select(i => $"T{i}")
+            .ToImmutableArray();
+        string separatedTemplateArgs = string.Join(", ", templateArgNames);
+
+        sb.AppendLine($"#region <{separatedTemplateArgs}>");
+
+        string resultValueType = templateArgNames.Length == 1 ? separatedTemplateArgs : $"({separatedTemplateArgs})";
+        string resultValueExpansion = GenerateResultValueExpansion(templateArgNames);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
+        public static ref readonly Result<{{resultValueType}}> Tap<{{separatedTemplateArgs}}>(this in Result<{{resultValueType}}> result, Action<{{separatedTemplateArgs}}>? onSuccess = null, Action<Error>? onFailure = null)
+        {
+            switch (result.State)
+            {
+                case ResultState.Success:
+                    onSuccess?.Invoke({{resultValueExpansion}});
+                    break;
+                case ResultState.Error:
+                    onFailure?.Invoke(result.Error!);
+                    break;
+
+                default: throw new ResultNotInitializedException(nameof(result));
+            }
+            return ref result;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
+        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Task<Result<{{resultValueType}}>> resultTask, Action<{{separatedTemplateArgs}}>? onSuccess = null, Action<Error>? onFailure = null)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            switch (result.State)
+            {
+                case ResultState.Success:
+                    onSuccess?.Invoke({{resultValueExpansion}});
+                    break;
+                case ResultState.Error:
+                    onFailure?.Invoke(result.Error!);
+                    break;
+
+                default: throw new ResultNotInitializedException(nameof(resultTask));
+            }
+            return result;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
+        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Result<{{resultValueType}}> result, Func<{{separatedTemplateArgs}}, Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
+        {
+            switch (result.State)
+            {
+                case ResultState.Success:
+                    if (onSuccess is not null)
+                        await onSuccess.Invoke({{resultValueExpansion}}).ConfigureAwait(false);
+                    break;
+                case ResultState.Error:
+                    if (onFailure is not null)
+                        await onFailure.Invoke(result.Error!).ConfigureAwait(false);
+                    break;
+
+                default: throw new ResultNotInitializedException(nameof(result));
+            }
+            return result;
+        }
+        """);
+
+        sb.AppendLine($$"""
+        [PureAttribute]
+        [GeneratedCodeAttribute("{{nameof(ResultTapExecutor)}}", "1.0.0.0")]
+        public static async Task<Result<{{resultValueType}}>> Tap<{{separatedTemplateArgs}}>(this Task<Result<{{resultValueType}}>> resultTask, Func<{{separatedTemplateArgs}}, Task>? onSuccess = null, Func<Error, Task>? onFailure = null)
+        {
+            var result = await resultTask.ConfigureAwait(false);
+            switch (result.State)
+            {
+                case ResultState.Success:
+                    if (onSuccess is not null)
+                        await onSuccess.Invoke({{resultValueExpansion}}).ConfigureAwait(false);
+                    break;
+                case ResultState.Error:
+                    if (onFailure is not null)
+                        await onFailure.Invoke(result.Error!).ConfigureAwait(false);
+                    break;
+
+                default: throw new ResultNotInitializedException(nameof(resultTask));
+            }
+            return result;
+        }
+        """);
+
+        sb.AppendLine("#endregion");
+    }
+}