Handle error conditions from Lambda function in Runtime API

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Extensions/InvokeResponseExtensions.cs

@@ -38,32 +38,48 @@ public static APIGatewayProxyResponse ToApiGatewayProxyResponse(this InvokeRespo
         }
         catch
         {
-            if (emulatorMode == ApiGatewayEmulatorMode.Rest)
+            return ToApiGatewayErrorResponse(emulatorMode);
+        }
+    }
+
+    /// <summary>
+    /// Creates an API Gateway error response based on the emulator mode.
+    /// </summary>
+    /// <param name="emulatorMode">The API Gateway emulator mode (Rest or Http).</param>
+    /// <returns>An APIGatewayProxyResponse object representing the error response.</returns>
+    /// <remarks>
+    /// This method generates different error responses based on the API Gateway emulator mode:
+    /// - For Rest mode: Returns a response with StatusCode 502 and a generic error message.
+    /// - For Http mode: Returns a response with StatusCode 500 and a generic error message.
+    /// Both responses include a Content-Type header set to application/json.
+    /// </remarks>
+    public static APIGatewayProxyResponse ToApiGatewayErrorResponse(ApiGatewayEmulatorMode emulatorMode)
+    {
+        if (emulatorMode == ApiGatewayEmulatorMode.Rest)
+        {
+            return new APIGatewayProxyResponse
             {
-                return new APIGatewayProxyResponse
-                {
-                    StatusCode = 502,
-                    Body = "{\"message\":\"Internal server error\"}",
-                    Headers = new Dictionary<string, string>
+                StatusCode = 502,
+                Body = "{\"message\":\"Internal server error\"}",
+                Headers = new Dictionary<string, string>
                 {
                     { "Content-Type", "application/json" }
                 },
-                    IsBase64Encoded = false
-                };
-            }
-            else
+                IsBase64Encoded = false
+            };
+        }
+        else
+        {
+            return new APIGatewayProxyResponse
             {
-                return new APIGatewayProxyResponse
-                {
-                    StatusCode = 500,
-                    Body = "{\"message\":\"Internal Server Error\"}",
-                    Headers = new Dictionary<string, string>
+                StatusCode = 500,
+                Body = "{\"message\":\"Internal Server Error\"}",
+                Headers = new Dictionary<string, string>
                 {
                     { "Content-Type", "application/json" }
                 },
-                    IsBase64Encoded = false
-                };
-            }
+                IsBase64Encoded = false
+            };
         }
     }
 
@@ -137,16 +153,7 @@ private static APIGatewayHttpApiV2ProxyResponse ToHttpApiV2Response(string respo
                 catch
                 {
                     // If deserialization fails, return Internal Server Error
-                    return new APIGatewayHttpApiV2ProxyResponse
-                    {
-                        StatusCode = 500,
-                        Body = "{\"message\":\"Internal Server Error\"}",
-                        Headers = new Dictionary<string, string>
-                    {
-                        { "Content-Type", "application/json" }
-                    },
-                        IsBase64Encoded = false
-                    };
+                    return ToHttpApiV2ErrorResponse();
                 }
             }
 
@@ -177,4 +184,29 @@ private static APIGatewayHttpApiV2ProxyResponse ToHttpApiV2Response(string respo
         };
     }
 
+    /// <summary>
+    /// Creates a standard HTTP API v2 error response.
+    /// </summary>
+    /// <returns>An APIGatewayHttpApiV2ProxyResponse object representing the error response.</returns>
+    /// <remarks>
+    /// This method generates a standard error response for HTTP API v2:
+    /// - StatusCode is set to 500 (Internal Server Error).
+    /// - Body contains a JSON string with a generic error message.
+    /// - Headers include a Content-Type set to application/json.
+    /// - IsBase64Encoded is set to false.
+    /// </remarks>
+    public static APIGatewayHttpApiV2ProxyResponse ToHttpApiV2ErrorResponse()
+    {
+        return new APIGatewayHttpApiV2ProxyResponse
+        {
+            StatusCode = 500,
+            Body = "{\"message\":\"Internal Server Error\"}",
+            Headers = new Dictionary<string, string>
+            {
+                { "Content-Type", "application/json" }
+            },
+            IsBase64Encoded = false
+        };
+    }
+
 }

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Processes/ApiGatewayEmulatorProcess.cs

@@ -99,24 +99,35 @@ public static ApiGatewayEmulatorProcess Startup(RunCommandSettings settings, Can
             using var lambdaClient = CreateLambdaServiceClient(routeConfig, settings);
             var response =  await lambdaClient.InvokeAsync(invokeRequest);
 
-            if (response.FunctionError != null)
+            if (response.FunctionError == null) // response is successful
             {
-                // TODO: Mimic API Gateway's behavior when Lambda function has an exception during invocation.
-                context.Response.StatusCode = 500;
-                return;
-            }
-
-            // Convert API Gateway response object returned from Lambda to ASP.NET Core response.
-            if (settings.ApiGatewayEmulatorMode.Equals(ApiGatewayEmulatorMode.HttpV2))
-            {
-                var lambdaResponse = response.ToApiGatewayHttpApiV2ProxyResponse();
-                await lambdaResponse.ToHttpResponseAsync(context);
+                if (settings.ApiGatewayEmulatorMode.Equals(ApiGatewayEmulatorMode.HttpV2))
+                {
+                    var lambdaResponse = response.ToApiGatewayHttpApiV2ProxyResponse();
+                    await lambdaResponse.ToHttpResponseAsync(context);
+                }
+                else
+                {
+                    var lambdaResponse = response.ToApiGatewayProxyResponse(settings.ApiGatewayEmulatorMode.Value);
+                    await lambdaResponse.ToHttpResponseAsync(context, settings.ApiGatewayEmulatorMode.Value);
+                }
             }
             else
             {
-                var lambdaResponse = response.ToApiGatewayProxyResponse(settings.ApiGatewayEmulatorMode.Value);
-                await lambdaResponse.ToHttpResponseAsync(context, settings.ApiGatewayEmulatorMode.Value);
+                // For function errors, api gateway just displays them as an internal server error, so we convert them to the correct error response here.
+
+                if (settings.ApiGatewayEmulatorMode.Equals(ApiGatewayEmulatorMode.HttpV2))
+                {
+                    var lambdaResponse = InvokeResponseExtensions.ToHttpApiV2ErrorResponse();
+                    await lambdaResponse.ToHttpResponseAsync(context);
+                }
+                else
+                {
+                    var lambdaResponse = InvokeResponseExtensions.ToApiGatewayErrorResponse(settings.ApiGatewayEmulatorMode.Value);
+                    await lambdaResponse.ToHttpResponseAsync(context, settings.ApiGatewayEmulatorMode.Value);
+                }
             }
+
         });
 
         var runTask = app.RunAsync(cancellationToken);

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Properties/AssemblyInfo.cs

@@ -0,0 +1,6 @@
+// Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
+// SPDX-License-Identifier: Apache-2.0
+
+using System.Runtime.CompilerServices;
+
+[assembly: InternalsVisibleTo("Amazon.Lambda.TestTool.UnitTests")]

Tools/LambdaTestTool-v2/src/Amazon.Lambda.TestTool/Services/LambdaRuntimeAPI.cs

@@ -1,7 +1,6 @@
 // Copyright Amazon.com, Inc. or its affiliates. All Rights Reserved.
 // SPDX-License-Identifier: Apache-2.0
 
-using System.Collections.Concurrent;
 using System.Text;
 using Amazon.Lambda.TestTool.Models;
 using Microsoft.AspNetCore.Mvc;
@@ -15,7 +14,7 @@ public class LambdaRuntimeApi
 
     private readonly IRuntimeApiDataStoreManager _runtimeApiDataStoreManager;
 
-    private LambdaRuntimeApi(WebApplication app)
+    internal LambdaRuntimeApi(WebApplication app)
     {
         _runtimeApiDataStoreManager = app.Services.GetRequiredService<IRuntimeApiDataStoreManager>();
 
@@ -63,16 +62,31 @@ public async Task PostEvent(HttpContext ctx, string functionName)
         if (isRequestResponseMode)
         {
             evnt.WaitForCompletion();
-            var result = Results.Ok(evnt.Response);
-            ctx.Response.StatusCode = 200;
 
-            if (!string.IsNullOrEmpty(evnt.Response))
+            if (evnt.EventStatus == EventContainer.Status.Success)
             {
-                var responseData = Encoding.UTF8.GetBytes(evnt.Response);
-                ctx.Response.Headers.ContentType = "application/json";
-                ctx.Response.Headers.ContentLength = responseData.Length;
-
-                await ctx.Response.Body.WriteAsync(responseData);
+                var result = Results.Ok(evnt.Response);
+                ctx.Response.StatusCode = 200;
+
+                if (!string.IsNullOrEmpty(evnt.Response))
+                {
+                    var responseData = Encoding.UTF8.GetBytes(evnt.Response);
+                    ctx.Response.Headers.ContentType = "application/json";
+                    ctx.Response.Headers.ContentLength = responseData.Length;
+                    await ctx.Response.Body.WriteAsync(responseData);
+                }
+            }
+            else
+            {
+                ctx.Response.StatusCode = 200;
+                ctx.Response.Headers["X-Amz-Function-Error"] = evnt.ErrorType;
+                if (!string.IsNullOrEmpty(evnt.ErrorResponse))
+                {
+                    var errorData = Encoding.UTF8.GetBytes(evnt.ErrorResponse);
+                    ctx.Response.Headers.ContentType = "application/json";
+                    ctx.Response.Headers.ContentLength = errorData.Length;
+                    await ctx.Response.Body.WriteAsync(errorData);
+                }
             }
             evnt.Dispose();
         }