refactor(source-generators): improve type casting and output generation

Directory.Build.props

@@ -1,6 +1,6 @@
 <Project>
   <PropertyGroup>
-    <Version>2.0.0-beta.9</Version>
+    <Version>2.0.0-beta.10</Version>
     <!-- SPDX license identifier for MIT -->
     <PackageLicenseExpression>MIT</PackageLicenseExpression>
     <!-- Other useful metadata -->

src/MinimalLambda.SourceGenerators/Extensions/DelegateInfoExtensions.cs

@@ -6,51 +6,12 @@ namespace MinimalLambda.SourceGenerators.Extensions;
 
 internal static class DelegateInfoExtensions
 {
-    internal static string BuildHandlerSignature(this DelegateInfo delegateInfo)
-    {
-        // build handler function signature
-        var signatureBuilder = new StringBuilder();
-        signatureBuilder.Append(delegateInfo.DelegateType);
-
-        // angle brackets needed for any parameters or a response type
-        if (
-            delegateInfo.Parameters.Count > 0
-            || delegateInfo.ReturnTypeInfo.FullyQualifiedType != TypeConstants.Void
-        )
-        {
-            signatureBuilder.Append("<");
-
-            // join parameters with comma
-            if (delegateInfo.Parameters.Count > 0)
-                signatureBuilder.Append(
-                    string.Join(
-                        ", ",
-                        delegateInfo.Parameters.Select(p => p.TypeInfo.FullyQualifiedType)
-                    )
-                );
-
-            if (delegateInfo.ReturnTypeInfo.FullyQualifiedType != TypeConstants.Void)
-            {
-                // add comma if there are parameters, i.e. this is the last in the list
-                if (delegateInfo.Parameters.Count > 0)
-                    signatureBuilder.Append(", ");
-                signatureBuilder.Append(delegateInfo.ReturnTypeInfo.FullyQualifiedType);
-            }
-
-            signatureBuilder.Append(">");
-        }
-
-        var handlerSignature = signatureBuilder.ToString();
-
-        return handlerSignature;
-    }
-
     extension(DelegateInfo delegateInfo)
     {
         internal string BuildHandlerCastCall()
         {
             var signatureBuilder = new StringBuilder();
-            signatureBuilder.Append("Cast(handler, ");
+            signatureBuilder.Append("Utilities.Cast(handler, ");
 
             signatureBuilder.Append(delegateInfo.ReturnTypeInfo.FullyQualifiedType);
 

src/MinimalLambda.SourceGenerators/OutputGenerators/LambdaHostOutputGenerator.cs

@@ -29,7 +29,23 @@ string generatorVersion
         var generatedCodeAttribute =
             $"[GeneratedCode(\"{generatorName}\", \"{generatorVersion}\")]";
 
-        List<string?> outputs = [CommonSources.Generate(generatedCodeAttribute)];
+        List<string?> outputs =
+        [
+            CommonSources.Generate(generatedCodeAttribute),
+            """
+                namespace MinimalLambda.Generated
+                {
+                    using System;
+                    using System.CodeDom.Compiler;
+                    using System.Runtime.CompilerServices;
+                    using System.Threading;
+                    using System.Threading.Tasks;
+                    using Microsoft.Extensions.DependencyInjection;
+                    using MinimalLambda;
+                    using MinimalLambda.Builder;
+
+                """,
+        ];
 
         // if MapHandler calls found, generate the source code.
         if (compilationInfo.MapHandlerInvocationInfos.Count >= 1)
@@ -67,6 +83,16 @@ string generatorVersion
                 )
             );
 
+        outputs.Add(
+            """
+                file static class Utilities
+                {
+                    internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+                }
+            }
+            """
+        );
+
         // join all the source code together and add it to the compilation context.
         var outCode = string.Join("\n", outputs.Where(s => s != null));
 

src/MinimalLambda.SourceGenerators/OutputGenerators/MapHandlerSources.cs

@@ -18,7 +18,7 @@ string generatedCodeAttribute
             var delegateInfo = mapHandlerInvocationInfo.DelegateInfo;
 
             // build handler function signature
-            var handlerSignature = delegateInfo.BuildHandlerSignature();
+            var handlerSignature = delegateInfo.BuildHandlerCastCall();
 
             // build out assignment statements for each handler parameter
             var handlerArgs = delegateInfo.BuildHandlerParameterAssignment();

src/MinimalLambda.SourceGenerators/Templates/GenericHandler.scriban

@@ -1,13 +1,3 @@
-namespace MinimalLambda.Generated
-{
-    using System;
-    using System.CodeDom.Compiler;
-    using System.Runtime.CompilerServices;
-    using System.Threading;
-    using System.Threading.Tasks;
-    using Microsoft.Extensions.DependencyInjection;
-    using MinimalLambda.Builder;
-
     {{ generated_code_attribute }}
     file static class GeneratedLambda{{ name }}BuilderExtensions
     {
@@ -50,7 +40,4 @@ namespace MinimalLambda.Generated
 
         {{~ end ~}}
         {{~ end ~}}
-
-        private static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
-    }
-}
+    }

src/MinimalLambda.SourceGenerators/Templates/MapHandler.scriban

@@ -1,13 +1,3 @@
-namespace MinimalLambda.Generated
-{
-    using System;
-    using System.CodeDom.Compiler;
-    using System.Runtime.CompilerServices;
-    using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
-    using Microsoft.Extensions.DependencyInjection;
-
     {{ generated_code_attribute }}
     file static class GeneratedLambdaInvocationBuilderExtensions
     {
@@ -21,7 +11,7 @@ namespace MinimalLambda.Generated
             Delegate handler
         )
         {
-            var castHandler = ({{ call.handler_signature }})handler;
+            var castHandler = {{ call.handler_signature }};
 
             application.Handle(InvocationDelegate);
             {{~ if call.is_event_feature_required ~}}
@@ -72,4 +62,3 @@ namespace MinimalLambda.Generated
         }
         {{~ end ~}}
     }
-}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_AllInputSources#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Action<string, global::Amazon.Lambda.Core.ILambdaContext, global::System.Threading.CancellationToken, global::IService, global::IService?, global::IService, global::IService?>)handler;
+            var castHandler = Utilities.Cast(handler, void (string arg0, global::Amazon.Lambda.Core.ILambdaContext arg1, global::System.Threading.CancellationToken arg2, global::IService arg3, global::IService? arg4, global::IService arg5, global::IService? arg6) => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -84,4 +85,9 @@ Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_Async_ReturnTaskString_TypeCast#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Func<global::System.Threading.Tasks.Task<string>>)handler;
+            var castHandler = Utilities.Cast(handler, global::System.Threading.Tasks.Task<string> () => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -70,4 +71,9 @@ async Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_NoReturn_TypeCast#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Action<string, global::IService>)handler;
+            var castHandler = Utilities.Cast(handler, void (string arg0, global::IService arg1) => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -70,4 +71,9 @@ Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_NoTypeInfo_TypeCast#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Func<global::IService, string, string>)handler;
+            var castHandler = Utilities.Cast(handler, string (global::IService arg0, string arg1) => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -75,4 +76,9 @@ Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_ReturnExplicitType#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Func<string, global::IService, global::IService>)handler;
+            var castHandler = Utilities.Cast(handler, global::IService (string arg0, global::IService arg1) => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -80,4 +81,9 @@ Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}

tests/MinimalLambda.SourceGenerators.UnitTests/Snapshots/BlockLambdaVerifyTests.Test_BlockLambda_ReturnImplicitNullable#LambdaHandler.g.verified.cs

@@ -31,10 +31,11 @@ namespace MinimalLambda.Generated
     using System;
     using System.CodeDom.Compiler;
     using System.Runtime.CompilerServices;
+    using System.Threading;
     using System.Threading.Tasks;
-    using MinimalLambda.Builder;
-    using MinimalLambda;
     using Microsoft.Extensions.DependencyInjection;
+    using MinimalLambda;
+    using MinimalLambda.Builder;
 
     [GeneratedCode("MinimalLambda.SourceGenerators", "0.0.0")]
     file static class GeneratedLambdaInvocationBuilderExtensions
@@ -48,7 +49,7 @@ internal static ILambdaInvocationBuilder MapHandlerInterceptor0(
             Delegate handler
         )
         {
-            var castHandler = (global::System.Func<string, global::IService, string?>)handler;
+            var castHandler = Utilities.Cast(handler, string? (string arg0, global::IService arg1) => throw null!);
 
             application.Handle(InvocationDelegate);
 
@@ -80,4 +81,9 @@ Task InvocationDelegate(ILambdaInvocationContext context)
             }
         }
     }
-}
+
+    file static class Utilities
+    {
+        internal static T Cast<T>(Delegate d, T _) where T : Delegate => (T)d;
+    }
+}