Improve error message when binding a command with arguments into normal button

Author: exyi

src/Framework/Framework/Compilation/Javascript/ParametrizedCode.cs

@@ -50,9 +50,14 @@ public ParametrizedCode(string code, OperatorPrecedence precedence = default)
 
         // TODO(exyi): add WriteTo(StringBuilder)
         /// <summary>
-        /// Converts this to string and assigns all parameters using `parameterAssignment`. If there is any missing, exception is thrown.
+        /// Converts this to string and assigns all parameters using `parameterAssignment`.
         /// </summary>
+        /// <exception cref="MissingAssignmentException">Thrown when some parameter is not assigned and has no default value.</exception>
         public string ToString(Func<CodeSymbolicParameter, CodeParameterAssignment> parameterAssignment) => ToString(parameterAssignment, out var _);
+        /// <summary>
+        /// Converts this to string and assigns all parameters using `parameterAssignment`.
+        /// </summary>
+        /// <exception cref="MissingAssignmentException">Thrown when some parameter is not assigned and has no default value.</exception>
         public string ToString(Func<CodeSymbolicParameter, CodeParameterAssignment> parameterAssignment, out bool allIsDefault)
         {
             allIsDefault = true;
@@ -205,7 +210,7 @@ private CodeParameterAssignment[] FindAssignment(Func<CodeSymbolicParameter, Cod
                     {
                         pp[i] = parameters[i].DefaultAssignment;
                         if (pp[i].Code == null)
-                            throw new InvalidOperationException($"Assignment of parameter '{parameters[i].Parameter}' was not found.");
+                            throw new MissingAssignmentException(parameters[i], this);
                     }
                 }
                 else
@@ -229,6 +234,11 @@ public IEnumerable<CodeSymbolicParameter> EnumerateAllParameters()
             }
         }
 
+        public record MissingAssignmentException(CodeParameterInfo Parameter, ParametrizedCode FullCode): RecordExceptions.RecordException
+        {
+            public override string Message => $"Assignment of parameter '{Parameter.Parameter}' was not found.";
+        }
+
         /// <summary>
         /// Builder class with reasonably fast Add operation. Use Build method to convert it to immutable ParametrizedCode
         /// </summary>

src/Framework/Framework/Controls/KnockoutHelper.cs

@@ -9,6 +9,7 @@
 using DotVVM.Framework.Compilation.Javascript.Ast;
 using DotVVM.Framework.Configuration;
 using DotVVM.Framework.Utils;
+using FastExpressionCompiler;
 using Newtonsoft.Json;
 
 namespace DotVVM.Framework.Controls
@@ -263,18 +264,26 @@ options.KoContext is object ?
 
             string SubstituteArguments(ParametrizedCode parametrizedCode)
             {
-                return parametrizedCode.ToString(p =>
-                    p == JavascriptTranslator.CurrentElementParameter ? options.ElementAccessor :
-                    p == CommandBindingExpression.CurrentPathParameter ? CodeParameterAssignment.FromIdentifier(getContextPath(control)) :
-                    p == CommandBindingExpression.ControlUniqueIdParameter ? uniqueControlId?.GetParametrizedJsExpression(control) ?? CodeParameterAssignment.FromLiteral("") :
-                    p == JavascriptTranslator.KnockoutContextParameter ? knockoutContext :
-                    p == JavascriptTranslator.KnockoutViewModelParameter ? viewModel :
-                    p == CommandBindingExpression.OptionalKnockoutContextParameter ? optionalKnockoutContext :
-                    p == CommandBindingExpression.CommandArgumentsParameter ? options.CommandArgs ?? default :
-                    p == CommandBindingExpression.PostbackHandlersParameter ? CodeParameterAssignment.FromIdentifier(getHandlerScript()) :
-                    p == CommandBindingExpression.AbortSignalParameter ? abortSignal :
-                    default
-                );
+                try
+                {
+                    return parametrizedCode.ToString(p =>
+                        p == JavascriptTranslator.CurrentElementParameter ? options.ElementAccessor :
+                        p == CommandBindingExpression.CurrentPathParameter ? CodeParameterAssignment.FromIdentifier(getContextPath(control)) :
+                        p == CommandBindingExpression.ControlUniqueIdParameter ? uniqueControlId?.GetParametrizedJsExpression(control) ?? CodeParameterAssignment.FromLiteral("") :
+                        p == JavascriptTranslator.KnockoutContextParameter ? knockoutContext :
+                        p == JavascriptTranslator.KnockoutViewModelParameter ? viewModel :
+                        p == CommandBindingExpression.OptionalKnockoutContextParameter ? optionalKnockoutContext :
+                        p == CommandBindingExpression.CommandArgumentsParameter ? options.CommandArgs ?? default :
+                        p == CommandBindingExpression.PostbackHandlersParameter ? CodeParameterAssignment.FromIdentifier(getHandlerScript()) :
+                        p == CommandBindingExpression.AbortSignalParameter ? abortSignal :
+                        default
+                    );
+                }
+                catch (ParametrizedCode.MissingAssignmentException e) when (e.Parameter.Parameter == CommandBindingExpression.CommandArgumentsParameter)
+                {
+                    var returnType = expression.GetProperty<ResultTypeBindingProperty>(ErrorHandlingMode.ReturnNull)?.Type;
+                    throw new DotvvmControlException(control, $"The binding {expression} of type {returnType?.ToCode(stripNamespace: true) ?? "?"} requires arguments, but none were provided to the KnockoutHelper.GenerateClientPostback method.", innerException: e) { RelatedBinding = expression };
+                }
             }
         }