[wasm] marshling call to assembly entrypoint via new interop (#73156)

- added JavaScriptExports.CallEntrypoint replacing legacy mono_bind_assembly_entry_point
- moved legacy imports and split RuntimeHelpers
- simplified dotnet-legacy.d.ts
- set_arg_type on manually written JavaScriptExports calls

Co-authored-by: Katelyn Gadd <kg@luminance.org>
Co-authored-by: Marek Fišera <mara@neptuo.com>

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptExports.cs

@@ -1,14 +1,94 @@
 // Licensed to the .NET Foundation under one or more agreements.
 // The .NET Foundation licenses this file to you under the MIT license.
 
+using System.Reflection;
 using System.Runtime.CompilerServices;
+using System.Threading.Tasks;
 
 namespace System.Runtime.InteropServices.JavaScript
 {
     // this maps to src\mono\wasm\runtime\corebindings.ts
     // the methods are protected from trimming by DynamicDependency on JSFunctionBinding.BindJSFunction
     internal static unsafe partial class JavaScriptExports
     {
+        [MethodImpl(MethodImplOptions.NoInlining)] // https://github.com/dotnet/runtime/issues/71425
+        // the marshaled signature is:
+        // Task<int>? CallEntrypoint(MonoMethod* entrypointPtr, string[] args)
+        public static void CallEntrypoint(JSMarshalerArgument* arguments_buffer)
+        {
+            ref JSMarshalerArgument arg_exc = ref arguments_buffer[0]; // initialized by caller in alloc_stack_frame()
+            ref JSMarshalerArgument arg_result = ref arguments_buffer[1]; // initialized by caller in alloc_stack_frame()
+            ref JSMarshalerArgument arg_1 = ref arguments_buffer[2]; // initialized and set by caller
+            ref JSMarshalerArgument arg_2 = ref arguments_buffer[3]; // initialized and set by caller
+            try
+            {
+                arg_1.ToManaged(out IntPtr entrypointPtr);
+                if (entrypointPtr == IntPtr.Zero)
+                {
+                    throw new MissingMethodException("Missing entrypoint");
+                }
+
+                RuntimeMethodHandle methodHandle = JSHostImplementation.GetMethodHandleFromIntPtr(entrypointPtr);
+                // this would not work for generic types. But Main() could not be generic, so we are fine.
+                MethodInfo? method = MethodBase.GetMethodFromHandle(methodHandle) as MethodInfo;
+                if (method == null)
+                {
+                    throw new InvalidProgramException("Can't resolve entrypoint handle");
+                }
+
+                arg_2.ToManaged(out string?[]? args);
+                object[] argsToPass = System.Array.Empty<object>();
+                Task<int>? result = null;
+                var parameterInfos = method.GetParameters();
+                if (parameterInfos.Length > 0 && parameterInfos[0].ParameterType == typeof(string[]))
+                {
+                    argsToPass = new object[] { args ?? System.Array.Empty<string>() };
+                }
+                if (method.ReturnType == typeof(void))
+                {
+                    method.Invoke(null, argsToPass);
+                }
+                else if (method.ReturnType == typeof(int))
+                {
+                    int intResult = (int)method.Invoke(null, argsToPass)!;
+                    result = Task.FromResult(intResult);
+                }
+                else if (method.ReturnType == typeof(Task))
+                {
+                    Task methodResult = (Task)method.Invoke(null, argsToPass)!;
+                    TaskCompletionSource<int> tcs = new TaskCompletionSource<int>();
+                    result = tcs.Task;
+                    methodResult.ContinueWith((t) =>
+                    {
+                        if (t.IsFaulted)
+                        {
+                            tcs.SetException(t.Exception!);
+                        }
+                        else
+                        {
+                            tcs.SetResult(0);
+                        }
+                    }, TaskScheduler.Default);
+                }
+                else if (method.ReturnType == typeof(Task<int>))
+                {
+                    result = (Task<int>)method.Invoke(null, argsToPass)!;
+                }
+                else
+                {
+                    throw new InvalidProgramException($"Return type '{method.ReturnType.FullName}' from main method in not supported");
+                }
+                arg_result.ToJS(result, (ref JSMarshalerArgument arg, int value) =>
+                {
+                    arg.ToJS(value);
+                });
+            }
+            catch (Exception ex)
+            {
+                arg_exc.ToJS(ex);
+            }
+        }
+
 
         // The JS layer invokes this method when the JS wrapper for a JS owned object
         //  has been collected by the JS garbage collector

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Marshaling/JSMarshalerArgument.Task.cs

@@ -175,9 +175,9 @@ static void MarshalResult(ref JSMarshalerArgument arg, object? taskResult)
         /// Implementation of the argument marshaling.
         /// It's used by JSImport code generator and should not be used by developers in source code.
         /// </summary>
-        public void ToJS(Task value)
+        public void ToJS(Task? value)
         {
-            Task task = value;
+            Task? task = value;
 
             if (task == null)
             {

src/mono/wasm/runtime/debug.ts

@@ -2,10 +2,11 @@
 // The .NET Foundation licenses this file to you under the MIT license.
 
 import Configuration from "consts:configuration";
-import { INTERNAL, Module, MONO, runtimeHelpers } from "./imports";
+import { INTERNAL, Module, runtimeHelpers } from "./imports";
 import { toBase64StringImpl } from "./base64";
 import cwraps from "./cwraps";
 import { VoidPtr, CharPtr } from "./types/emscripten";
+import { MONO } from "./net6-legacy/imports";
 const commands_received: any = new Map<number, CommandResponse>();
 const wasm_func_map = new Map<number, string>();
 commands_received.remove = function (key: number): CommandResponse { const value = this.get(key); this.delete(key); return value; };
@@ -34,7 +35,7 @@ regexes.push(/(?<replaceSection>[a-z]+:\/\/[^ )]*:wasm-function\[(?<funcNum>\d+)
 regexes.push(/(?<replaceSection><[^ >]+>[.:]wasm-function\[(?<funcNum>[0-9]+)\])/);
 
 export function mono_wasm_runtime_ready(): void {
-    runtimeHelpers.mono_wasm_runtime_is_ready = true;
+    INTERNAL.mono_wasm_runtime_is_ready = runtimeHelpers.mono_wasm_runtime_is_ready = true;
 
     // FIXME: where should this go?
     _next_call_function_res_id = 0;