Do not suppress original exceptions in ConfigureBuilder, Fix #695

src/Microsoft.AspNetCore.Hosting/Startup/ConfigureBuilder.cs

@@ -37,14 +37,14 @@ namespace Microsoft.AspNetCore.Hosting.Startup
                     {
                         parameters[index] = serviceProvider.GetRequiredService(parameterInfo.ParameterType);
                     }
-                    catch (Exception)
+                    catch (Exception ex)
                     {
                         throw new Exception(string.Format(
                             "Could not resolve a service of type '{0}' for the parameter '{1}' of method '{2}' on type '{3}'.",
                             parameterInfo.ParameterType.FullName,
                             parameterInfo.Name,
                             MethodInfo.Name,
-                            MethodInfo.DeclaringType.FullName));
+                            MethodInfo.DeclaringType.FullName), ex);
                     }
                 }
             }

test/Microsoft.AspNetCore.Hosting.Tests/Startup/ConfigureBuilderTests.cs

@@ -0,0 +1,54 @@
+// Copyright (c) .NET Foundation. All rights reserved.
+// Licensed under the Apache License, Version 2.0. See License.txt in the project root for license information.
+
+using System;
+using System.Reflection;
+using Microsoft.AspNetCore.Builder;
+using Microsoft.AspNetCore.Builder.Internal;
+using Microsoft.Extensions.DependencyInjection;
+using Xunit;
+
+namespace Microsoft.AspNetCore.Hosting.Startup.Tests 
+{
+    public class ConfigureBuilderTests
+    {
+        [Fact]
+        public void CapturesServiceExceptionDetails()
+        {
+            var methodInfo = GetType().GetMethod(nameof(InjectedMethod), BindingFlags.NonPublic | BindingFlags.Static);
+            Assert.NotNull(methodInfo);
+
+            var services = new ServiceCollection()
+                .AddSingleton<CrasherService>()
+                .BuildServiceProvider();
+
+            var applicationBuilder = new ApplicationBuilder(services);
+
+            var builder = new ConfigureBuilder(methodInfo);
+            Action<IApplicationBuilder> action = builder.Build(instance:null);
+            var ex = Assert.Throws<Exception>(() => action.Invoke(applicationBuilder));
+
+            Assert.NotNull(ex);
+            Assert.Equal($"Could not resolve a service of type '{typeof(CrasherService).FullName}' for the parameter"
+                + $" 'service' of method '{methodInfo.Name}' on type '{methodInfo.DeclaringType.FullName}'.", ex.Message);
+
+            // the inner exception contains the root cause
+            Assert.NotNull(ex.InnerException);
+            Assert.Equal("Service instantiation failed", ex.InnerException.Message);
+            Assert.Contains(nameof(CrasherService), ex.InnerException.StackTrace);
+        }
+
+        private static void InjectedMethod(CrasherService service)
+        {
+            Assert.NotNull(service);
+        }
+
+        private class CrasherService
+        {
+            public CrasherService()
+            {
+                throw new Exception("Service instantiation failed");
+            }
+        }
+    }
+}