aggregate errors

Author: mhoeger

src/DotNetWorker/Context/Features/DefaultModelBindingFeature.cs

@@ -1,9 +1,12 @@
-// Copyright (c) .NET Foundation. All rights reserved.
+g// Copyright (c) .NET Foundation. All rights reserved.
 // Licensed under the MIT License. See License.txt in the project root for license information.
 
 using System;
 using System.Collections.Generic;
+using System.Linq;
 using Microsoft.Azure.Functions.Worker.Converters;
+using Microsoft.Azure.Functions.Worker.Definition;
+using Microsoft.Azure.Functions.Worker.Diagnostics.Exceptions;
 
 namespace Microsoft.Azure.Functions.Worker.Context.Features
 {
@@ -31,6 +34,7 @@ public DefaultModelBindingFeature(IEnumerable<IConverter> converters)
             _parameterValues = new object?[context.FunctionDefinition.Parameters.Length];
             _inputBound = true;
 
+            List<string>? errors = null;
             for (int i = 0; i < _parameterValues.Length; i++)
             {
                 FunctionParameter param = context.FunctionDefinition.Parameters[i];
@@ -51,9 +55,21 @@ public DefaultModelBindingFeature(IEnumerable<IConverter> converters)
                 }
                 else if (source is not null)
                 {
-                    throw new InvalidCastException($"Cannot convert input parameter '{param.Name}' for Function '{context.FunctionDefinition.Name}' to type '{param.Type.FullName}' from type '{source.GetType().FullName}'.");
+                    // Don't initialize this list unless we have to
+                    if (errors is null)
+                    {
+                        errors = new List<string>();
+                    }
+
+                    errors.Add($"Cannot convert input parameter '{param.Name}' to type '{param.Type.FullName}' from type '{source.GetType().FullName}'.");
                 }
             }
+            
+            // found errors
+            if (errors is not null)
+            {
+                throw new FunctionInputConverterException($"Error converting {errors.Count} input parameters for Function '{context.FunctionDefinition.Name}': {string.Join(" ", errors)}");
+            }
 
             return _parameterValues;
         }

src/DotNetWorker/Diagnostics/Exceptions/FunctionInputConverterException.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.Azure.Functions.Worker.Diagnostics.Exceptions
+{
+    internal class FunctionInputConverterException : FunctionWorkerException
+    {
+        internal FunctionInputConverterException(string message) : base(message) { }
+
+        internal FunctionInputConverterException(string message, Exception innerException) : base(message, innerException) { }
+    }
+}

src/DotNetWorker/Diagnostics/Exceptions/FunctionWorkerException.cs

@@ -0,0 +1,18 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace Microsoft.Azure.Functions.Worker.Diagnostics
+{
+    /// <summary>
+    /// Internal exception that is surfaced to the user
+    /// </summary>
+    internal class FunctionWorkerException : Exception
+    {
+        internal FunctionWorkerException(string message) : base(message) { }
+
+        internal FunctionWorkerException(string message, Exception innerException) : base(message, innerException) { }
+    }
+}