Better error message from JSInterop when detecting an unconfigured module import

CHANGELOG.md

@@ -29,6 +29,8 @@ List of added functionality in this release.
 
 List of fixes in this release.
 
+- Fixed JSInterop error message when trying to import an unconfigured module (#398).
+
 - Fixed issue where a registered fall-back service provider was not made available to resolve service dependencies of components under test. Thanks to [@dady8889](https://github.com/dady8889) for the reporting the issue.
 
 ## [1.1.5] - 2021-04-30

src/bunit.web/JSInterop/JSRuntimeUnhandledInvocationException.cs

@@ -2,6 +2,7 @@
 using System.Linq;
 using System.Runtime.Serialization;
 using System.Text;
+using Microsoft.JSInterop;
 
 namespace Bunit
 {
@@ -13,6 +14,10 @@ namespace Bunit
 	[Serializable]
 	public sealed class JSRuntimeUnhandledInvocationException : Exception
 	{
+#if NET5_0_OR_GREATER
+		private const string DefaultImportIdentifier = "import";
+#endif
+
 		/// <summary>
 		/// Gets the unplanned invocation.
 		/// </summary>
@@ -53,22 +58,29 @@ private static string CreateErrorMessage(JSRuntimeInvocation invocation)
 			sb.AppendLine("Configure bUnit's JSInterop to handle the call with following:");
 			sb.AppendLine();
 
-			if (invocation.IsVoidResultInvocation)
+			if (IsImportModuleInvocation(invocation))
 			{
-				sb.AppendLine($"    SetupVoid({GetArguments(invocation)})");
+				sb.AppendLine($"    SetupModule({GetArguments(invocation, includeIdentifier: false)})");
 			}
 			else
 			{
-				sb.AppendLine($"    Setup<{GetReturnTypeName(invocation.ResultType)}>({GetArguments(invocation)})");
-			}
-
-			if (invocation.Arguments.Any())
-			{
-				sb.AppendLine("or the following, to match any arguments:");
 				if (invocation.IsVoidResultInvocation)
-					sb.AppendLine($"    SetupVoid(\"{invocation.Identifier}\", _ => true)");
+				{
+					sb.AppendLine($"    SetupVoid({GetArguments(invocation)})");
+				}
 				else
-					sb.AppendLine($"    Setup<{GetReturnTypeName(invocation.ResultType)}>(\"{invocation.Identifier}\", _ => true)");
+				{
+					sb.AppendLine($"    Setup<{GetReturnTypeName(invocation.ResultType)}>({GetArguments(invocation)})");
+				}
+
+				if (invocation.Arguments.Any())
+				{
+					sb.AppendLine("or the following, to match any arguments:");
+					if (invocation.IsVoidResultInvocation)
+						sb.AppendLine($"    SetupVoid(\"{invocation.Identifier}\", _ => true)");
+					else
+						sb.AppendLine($"    Setup<{GetReturnTypeName(invocation.ResultType)}>(\"{invocation.Identifier}\", _ => true)");
+				}
 			}
 
 			sb.AppendLine();
@@ -113,11 +125,26 @@ private static string GetGenericInvocationArguments(JSRuntimeInvocation invocati
 			}
 		}
 
-		private static string GetArguments(JSRuntimeInvocation invocation)
+#pragma warning disable S1172 // Unused method parameters should be removed
+		private static bool IsImportModuleInvocation(JSRuntimeInvocation invocation)
+#pragma warning restore S1172 // Unused method parameters should be removed
+		{
+#if NET5_0_OR_GREATER
+			return string.Equals(invocation.Identifier, DefaultImportIdentifier, StringComparison.Ordinal)
+				&& typeof(IJSObjectReference).IsAssignableFrom(invocation.ResultType);
+#else
+			return false;
+#endif
+		}
+
+		private static string GetArguments(JSRuntimeInvocation invocation, bool includeIdentifier = true)
 		{
 			var args = invocation.Arguments
-				.Select(x => x is string s ? $"\"{s}\"" : x?.ToString() ?? "null")
-				.Prepend($"\"{invocation.Identifier}\"");
+				.Select(x => x is string s ? $"\"{s}\"" : x?.ToString() ?? "null");
+			if (includeIdentifier)
+			{
+				args = args.Prepend($"\"{invocation.Identifier}\"");
+			}
 
 			return string.Join(", ", args);
 		}

tests/bunit.web.tests/JSInterop/JSRuntimeUnhandledInvocationExceptionTest.cs

@@ -1,13 +1,14 @@
 using System;
 using System.Diagnostics.CodeAnalysis;
 using AutoFixture.Xunit2;
+using Microsoft.JSInterop;
 using Xunit;
 
 namespace Bunit.JSInterop
 {
 	[SuppressMessage("StyleCop.CSharp.ReadabilityRules", "SA1118:Parameter should not span multiple lines", Justification = "Makes error message easier to read.")]
 	[SuppressMessage("Design", "CA1034:Nested types should not be visible", Justification = "Dummy types are visible for testing purposes.")]
-	public class JSRuntimeUnhandledInvocationExceptionTest
+	public partial class JSRuntimeUnhandledInvocationExceptionTest
 	{
 		private const string CodeIdent = "    ";
 

tests/bunit.web.tests/JSInterop/JSRuntimeUnhandledInvocationExceptionTest.net5.cs

@@ -0,0 +1,29 @@
+#if NET5_0_OR_GREATER
+using System;
+using System.Diagnostics.CodeAnalysis;
+using AutoFixture.Xunit2;
+using Microsoft.JSInterop;
+using Xunit;
+
+namespace Bunit.JSInterop
+{
+	public partial class JSRuntimeUnhandledInvocationExceptionTest
+	{
+		[Theory(DisplayName = "Message prints correctly when trying to import an unconfigured module")]
+		[AutoData]
+		public void Test036(string moduleName)
+		{
+			var identifier = "import";
+			var returnType = typeof(IJSObjectReference);
+			var invocationMethodName = "InvokeAsync";
+			var exectedErrorMessage = CreateExpectedErrorMessage(
+				$"{CodeIdent}{invocationMethodName}<{returnType.Name}>(\"{identifier}\", \"{moduleName}\")",
+				$"{CodeIdent}SetupModule(\"{moduleName}\")");
+
+			var sut = new JSRuntimeUnhandledInvocationException(new JSRuntimeInvocation(identifier, new object?[] { moduleName }, returnType, invocationMethodName));
+
+			Assert.Equal(exectedErrorMessage, sut.Message);
+		}
+	}
+}
+#endif