Support async main #17673
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| Original file line number | Diff line number | Diff line change |
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| @@ -0,0 +1,89 @@ | ||
| // 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. | ||
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| using System; | ||
| using System.Linq; | ||
| using System.Reflection; | ||
| using System.Threading.Tasks; | ||
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| namespace Microsoft.AspNetCore.Blazor.Hosting | ||
| { | ||
| internal static class EntrypointInvoker | ||
| { | ||
| // This method returns void because currently the JS side is not listening to any result, | ||
| // nor will it handle any exceptions. We handle all exceptions internally to this method. | ||
| // In the future we may want Blazor.start to return something that exposes the possibly-async | ||
| // entrypoint result to the JS caller. There's no requirement to do that today, and if we | ||
| // do change this it will be non-breaking. | ||
| public static void InvokeEntrypoint(string assemblyName, string[] args) | ||
| { | ||
| object entrypointResult; | ||
| try | ||
| { | ||
| var assembly = Assembly.Load(assemblyName); | ||
| var entrypoint = FindUnderlyingEntrypoint(assembly); | ||
| var @params = entrypoint.GetParameters().Length == 1 ? new object[] { args } : new object[] { }; | ||
| entrypointResult = entrypoint.Invoke(null, @params); | ||
| } | ||
| catch (Exception syncException) | ||
| { | ||
| HandleStartupException(syncException); | ||
| return; | ||
| } | ||
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| // If the entrypoint is async, handle async exceptions in the same way that we would | ||
| // have handled sync ones | ||
| if (entrypointResult is Task entrypointTask) | ||
| { | ||
| entrypointTask.ContinueWith(task => | ||
| { | ||
| if (task.Exception != null) | ||
| { | ||
| HandleStartupException(task.Exception); | ||
| } | ||
| }); | ||
| } | ||
| } | ||
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| private static MethodBase FindUnderlyingEntrypoint(Assembly assembly) | ||
| { | ||
| // This is the entrypoint declared in .NET metadata. In the case of async main, it's the | ||
| // compiler-generated wrapper method. Otherwise it's the developer-defined method. | ||
| var metadataEntrypointMethodBase = assembly.EntryPoint; | ||
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| // For "async Task Main", the C# compiler generates a method called "<Main>" | ||
| // that is marked as the assembly entrypoint. Detect this case, and instead of | ||
| // calling "<Whatever>", call the sibling "Whatever". | ||
| if (metadataEntrypointMethodBase.IsSpecialName) | ||
| { | ||
| var origName = metadataEntrypointMethodBase.Name; | ||
| var origNameLength = origName.Length; | ||
| if (origNameLength > 2) | ||
| { | ||
| var candidateMethodName = origName.Substring(1, origNameLength - 2); | ||
| var candidateMethod = metadataEntrypointMethodBase.DeclaringType.GetMethod( | ||
| candidateMethodName, | ||
| BindingFlags.Static | BindingFlags.Public | BindingFlags.NonPublic, | ||
| null, | ||
| metadataEntrypointMethodBase.GetParameters().Select(p => p.ParameterType).ToArray(), | ||
| null); | ||
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| if (candidateMethod != null) | ||
| { | ||
| return candidateMethod; | ||
| } | ||
| } | ||
| } | ||
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| // Either it's not async main, or for some reason we couldn't locate the underlying entrypoint, | ||
| // so use the one from assembly metadata. | ||
| return metadataEntrypointMethodBase; | ||
| } | ||
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| private static void HandleStartupException(Exception exception) | ||
| { | ||
| // Logs to console, and causes the error UI to appear | ||
| Console.Error.WriteLine(exception); | ||
| } | ||
| } | ||
| } | ||
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -0,0 +1,153 @@ | ||
| // 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. | ||
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| using System; | ||
| using System.IO; | ||
| using System.Reflection; | ||
| using System.Runtime.Loader; | ||
| using System.Threading.Tasks; | ||
| using Microsoft.CodeAnalysis; | ||
| using Microsoft.CodeAnalysis.CSharp; | ||
| using Xunit; | ||
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| namespace Microsoft.AspNetCore.Blazor.Hosting | ||
| { | ||
| public class EntrypointInvokerTest | ||
| { | ||
| [Theory] | ||
| [InlineData(false, false)] | ||
| [InlineData(false, true)] | ||
| [InlineData(true, false)] | ||
| [InlineData(true, true)] | ||
| public void InvokesEntrypoint_Sync_Success(bool hasReturnValue, bool hasParams) | ||
| { | ||
| // Arrange | ||
| var returnType = hasReturnValue ? "int" : "void"; | ||
| var paramsDecl = hasParams ? "string[] args" : string.Empty; | ||
| var returnStatement = hasReturnValue ? "return 123;" : "return;"; | ||
| var assembly = CompileToAssembly(@" | ||
| static " + returnType + @" Main(" + paramsDecl + @") | ||
| { | ||
| DidMainExecute = true; | ||
| " + returnStatement + @" | ||
| }", out var didMainExecute); | ||
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| // Act | ||
| EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }); | ||
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| // Assert | ||
| Assert.True(didMainExecute()); | ||
| } | ||
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| [Theory] | ||
| [InlineData(false, false)] | ||
| [InlineData(false, true)] | ||
| [InlineData(true, false)] | ||
| [InlineData(true, true)] | ||
| public void InvokesEntrypoint_Async_Success(bool hasReturnValue, bool hasParams) | ||
| { | ||
| // Arrange | ||
| var returnTypeGenericParam = hasReturnValue ? "<int>" : string.Empty; | ||
| var paramsDecl = hasParams ? "string[] args" : string.Empty; | ||
| var returnStatement = hasReturnValue ? "return 123;" : "return;"; | ||
| var assembly = CompileToAssembly(@" | ||
| public static TaskCompletionSource<object> ContinueTcs { get; } = new TaskCompletionSource<object>(); | ||
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| static async Task" + returnTypeGenericParam + @" Main(" + paramsDecl + @") | ||
| { | ||
| await ContinueTcs.Task; | ||
| DidMainExecute = true; | ||
| " + returnStatement + @" | ||
| }", out var didMainExecute); | ||
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| // Act/Assert 1: Waits for task | ||
| // The fact that we're not blocking here proves that we're not executing the | ||
| // metadata-declared entrypoint, as that would block | ||
| EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }); | ||
| Assert.False(didMainExecute()); | ||
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| // Act/Assert 2: Continues | ||
| var tcs = (TaskCompletionSource<object>)assembly.GetType("SomeApp.Program").GetProperty("ContinueTcs").GetValue(null); | ||
| tcs.SetResult(null); | ||
| Assert.True(didMainExecute()); | ||
| } | ||
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| [Fact] | ||
| public void InvokesEntrypoint_Sync_Exception() | ||
| { | ||
| // Arrange | ||
| var assembly = CompileToAssembly(@" | ||
| public static void Main() | ||
| { | ||
| DidMainExecute = true; | ||
| throw new InvalidTimeZoneException(""Test message""); | ||
| }", out var didMainExecute); | ||
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| // Act/Assert | ||
| // The fact that this doesn't throw shows that EntrypointInvoker is doing something | ||
| // to handle the exception. We can't assert about what it does here, because that | ||
| // would involve capturing console output, which isn't safe in unit tests. Instead | ||
| // we'll check this in E2E tests. | ||
| EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }); | ||
| Assert.True(didMainExecute()); | ||
| } | ||
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| [Fact] | ||
| public void InvokesEntrypoint_Async_Exception() | ||
| { | ||
| // Arrange | ||
| var assembly = CompileToAssembly(@" | ||
| public static TaskCompletionSource<object> ContinueTcs { get; } = new TaskCompletionSource<object>(); | ||
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| public static async Task Main() | ||
| { | ||
| await ContinueTcs.Task; | ||
| DidMainExecute = true; | ||
| throw new InvalidTimeZoneException(""Test message""); | ||
| }", out var didMainExecute); | ||
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| // Act/Assert 1: Waits for task | ||
| EntrypointInvoker.InvokeEntrypoint(assembly.FullName, new string[] { }); | ||
| Assert.False(didMainExecute()); | ||
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| // Act/Assert 2: Continues | ||
| // As above, we can't directly observe the exception handling behavior here, | ||
| // so this is covered in E2E tests instead. | ||
| var tcs = (TaskCompletionSource<object>)assembly.GetType("SomeApp.Program").GetProperty("ContinueTcs").GetValue(null); | ||
| tcs.SetResult(null); | ||
| Assert.True(didMainExecute()); | ||
| } | ||
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| private static Assembly CompileToAssembly(string mainMethod, out Func<bool> didMainExecute) | ||
| { | ||
| var syntaxTree = CSharpSyntaxTree.ParseText(@" | ||
| using System; | ||
| using System.Threading.Tasks; | ||
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| namespace SomeApp | ||
| { | ||
| public static class Program | ||
| { | ||
| public static bool DidMainExecute { get; private set; } | ||
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| " + mainMethod + @" | ||
| } | ||
| }"); | ||
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| var compilation = CSharpCompilation.Create( | ||
| $"TestAssembly-{Guid.NewGuid().ToString("D")}", | ||
| new[] { syntaxTree }, | ||
| new[] { MetadataReference.CreateFromFile(typeof(object).GetTypeInfo().Assembly.Location) }, | ||
| new CSharpCompilationOptions(OutputKind.ConsoleApplication)); | ||
| using var ms = new MemoryStream(); | ||
| var compilationResult = compilation.Emit(ms); | ||
| ms.Seek(0, SeekOrigin.Begin); | ||
| var assembly = AssemblyLoadContext.Default.LoadFromStream(ms); | ||
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| var didMainExecuteProp = assembly.GetType("SomeApp.Program").GetProperty("DidMainExecute"); | ||
| didMainExecute = () => (bool)didMainExecuteProp.GetValue(null); | ||
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| return assembly; | ||
| } | ||
| } | ||
| } |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
| @@ -1,11 +1,12 @@ | ||
| <Project Sdk="Microsoft.NET.Sdk"> | ||
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| <PropertyGroup> | ||
| <TargetFramework>$(DefaultNetCoreTargetFramework)</TargetFramework> | ||
| </PropertyGroup> | ||
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| <ItemGroup> | ||
| <Reference Include="Microsoft.AspNetCore.Blazor" /> | ||
| <Reference Include="Microsoft.CodeAnalysis.CSharp" /> | ||
| </ItemGroup> | ||
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| </Project> |
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| Original file line number | Diff line number | Diff line change |
|---|---|---|
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@@ -11,8 +11,7 @@ let assembly_load: (assemblyName: string) => number; | |
| let find_class: (assemblyHandle: number, namespace: string, className: string) => number; | ||
| let find_method: (typeHandle: number, methodName: string, unknownArg: number) => MethodHandle; | ||
| let invoke_method: (method: MethodHandle, target: System_Object, argsArrayPtr: number, exceptionFlagIntPtr: number) => System_Object; | ||
| let mono_string_array_new: (length: number) => System_Array<System_String>; | ||
| let mono_string_get_utf8: (managedString: System_String) => Mono.Utf8Ptr; | ||
| let mono_string: (jsString: string) => System_String; | ||
| const appBinDirName = 'appBinDir'; | ||
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@@ -41,9 +40,18 @@ export const monoPlatform: Platform = { | |
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| findMethod: findMethod, | ||
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| callEntryPoint: function callEntryPoint(assemblyName: string) { | ||
| // Instead of using Module.mono_call_assembly_entry_point, we have our own logic for invoking | ||
| // the entrypoint which adds support for async main. | ||
| // Currently we disregard the return value from the entrypoint, whether it's sync or async. | ||
| // In the future, we might want Blazor.start to return a Promise<Promise<value>>, where the | ||
| // outer promise reflects the startup process, and the inner one reflects the possibly-async | ||
| // .NET entrypoint method. | ||
| const invokeEntrypoint = findMethod('Microsoft.AspNetCore.Blazor', 'Microsoft.AspNetCore.Blazor.Hosting', 'EntrypointInvoker', 'InvokeEntrypoint'); | ||
| this.callMethod(invokeEntrypoint, null, [ | ||
| this.toDotNetString(assemblyName), | ||
| mono_string_array_new(0) // In the future, we may have a way of supplying arg strings. For now, we always supply an empty string[]. | ||
| ]); | ||
| }, | ||
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| callMethod: function callMethod(method: MethodHandle, target: System_Object, args: System_Object[]): System_Object { | ||
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@@ -263,11 +271,9 @@ function createEmscriptenModuleInstance(loadAssemblyUrls: string[], onReady: () | |
| 'number', | ||
| ]); | ||
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There was a problem hiding this comment. You can image instead that There was a problem hiding this comment. If Mono adds native support for async main, I think they should create a new entrypoint API called something like
I don't think there's any problem on the JS side with needing to know the type in advance. There was a problem hiding this comment. Its possible to do this more reliably by calling the 'mono_assembly_get_object' mono API function which returns an MonoReflectionAssembly* mono_assembly_get_object (MonoDomain *domain, MonoAssembly *assembly); There was a problem hiding this comment. Thanks @vargaz - that's a great suggestion! I realised we don't need There was a problem hiding this comment. mono_assembly_get_object () would be a bit faster. Will look into adding it. |
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| mono_string_get_utf8 = Module.cwrap('mono_wasm_string_get_utf8', 'number', ['number']); | ||
| mono_string = Module.cwrap('mono_wasm_string_from_js', 'number', ['string']); | ||
| mono_string_array_new = Module.cwrap('mono_wasm_string_array_new', 'number', ['number']); | ||
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| MONO.loaded_files = []; | ||
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What's the reason why we need to call
Maininstead of<Main> ? Is this because<Main>(generated wrapper) contains aTask.GetAwaiter.GetResult()?There was a problem hiding this comment.
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Precisely