feat: catch error when cannot parse json input

Author: xavibel

src/Voxel.MiddyNet.HttpJsonBodyParserMiddleware/HttpJsonBodyParserMiddleware.cs

@@ -1,3 +1,4 @@
+using System;
 using Amazon.Lambda.APIGatewayEvents;
 using Newtonsoft.Json;
 using System.Threading.Tasks;
@@ -8,7 +9,16 @@ public class HttpJsonBodyParserMiddleware<T> : ILambdaMiddleware<APIGatewayProxy
     {
         public Task Before(APIGatewayProxyRequest lambdaEvent, MiddyNetContext context)
         {
-            var source = JsonConvert.DeserializeObject<T>(lambdaEvent.Body);
+            T source;
+            try
+            {
+                source = JsonConvert.DeserializeObject<T>(lambdaEvent.Body);
+            }
+            catch (JsonReaderException ex)
+            {
+                throw new Exception($"Error parsing \"{lambdaEvent.Body}\" to type {typeof(T)}");
+            }
+            
             context.AdditionalContext.Add("Body", source);
             return Task.CompletedTask;
         }

test/Voxel.MiddyNet.HttpJsonBodyParserMiddleware.Tests/HttpJsonBodyParserMiddlewareShould.cs

@@ -29,5 +29,22 @@ public async Task ProcessTheJsonRequest()
             context.AdditionalContext.ContainsKey("Body").Should().BeTrue();
             context.AdditionalContext["Body"].Should().BeEquivalentTo(expectation);
         }
+
+        [Fact]
+        public async Task ErrorWhenJsonNotMapsToObject()
+        {
+            var context = new MiddyNetContext(Substitute.For<ILambdaContext>());
+            var expectation = new TestObject("bar");
+            var source = "Not Mapped object" + JsonConvert.SerializeObject(expectation);
+            var request = new APIGatewayProxyRequest()
+            {
+                Headers = new Dictionary<string, string> { { "Content-Type", "application/json" } },
+                Body = source
+            };
+            var middleware = new HttpJsonBodyParserMiddleware<TestObject>();
+            Action action = () => middleware.Before(request, context);
+
+            action.Should().Throw<Exception>().WithMessage($"Error parsing \"{source}\" to type {typeof(TestObject)}");
+        }
     }
 }