[wasm][draft] make JSObject dynamic

src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.cs

@@ -109,7 +109,7 @@ public sealed class Any : JSType
 }
 
 [Versioning.SupportedOSPlatformAttribute("browser")]
-public class JSObject : IDisposable
+public class JSObject : IDisposable, System.Dynamic.IDynamicMetaObjectProvider
 {
     internal JSObject() { throw null; }
     public bool IsDisposed { get { throw null; } }
@@ -131,6 +131,8 @@ public class JSObject : IDisposable
     public void SetProperty(string propertyName, string? value) { throw null; }
     public void SetProperty(string propertyName, JSObject? value) { throw null; }
     public void SetProperty(string propertyName, byte[]? value) { throw null; }
+
+    public System.Dynamic.DynamicMetaObject GetMetaObject(System.Linq.Expressions.Expression parameter) => throw null;
 }
 
 [Versioning.SupportedOSPlatformAttribute("browser")]

src/libraries/System.Runtime.InteropServices.JavaScript/ref/System.Runtime.InteropServices.JavaScript.csproj

@@ -10,5 +10,6 @@
   <ItemGroup>
     <ProjectReference Include="..\..\System.Collections\ref\System.Collections.csproj" />
     <ProjectReference Include="..\..\System.Runtime\ref\System.Runtime.csproj" />
+    <ProjectReference Include="..\..\System.Linq.Expressions\ref\System.Linq.Expressions.csproj" />
   </ItemGroup>
 </Project>

src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj

@@ -14,6 +14,7 @@
 
   <ItemGroup>
     <Compile Include="System.Runtime.InteropServices.JavaScript.SupportedOSPlatform.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\JSObject.Dynamic.cs" />
   </ItemGroup>
 
   <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'Browser'">
@@ -76,6 +77,7 @@
     <Reference Include="System.Threading" />
     <Reference Include="System.Threading.Thread" />
     <Reference Include="System.Threading.Channels" />
+    <Reference Include="System.Linq.Expressions" />
   </ItemGroup>
 
   <ItemGroup>

src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSObject.Dynamic.cs

@@ -0,0 +1,50 @@
+// Licensed to the .NET Foundation under one or more agreements.
+// The .NET Foundation licenses this file to you under the MIT license.
+
+using System.Dynamic;
+using System.Linq.Expressions;
+
+namespace System.Runtime.InteropServices.JavaScript
+{
+    public partial class JSObject : IDynamicMetaObjectProvider
+    {
+        public DynamicMetaObject GetMetaObject(Expression parameter)
+        {
+            return new MetaDynamic(parameter, this);
+        }
+
+        private sealed class MetaDynamic : DynamicMetaObject
+        {
+            private JSObject proxy;
+
+            internal MetaDynamic(Expression expression, JSObject value)
+                : base(expression, BindingRestrictions.GetTypeRestriction(expression, typeof(JSObject)), value)
+            {
+                proxy = value;
+            }
+
+            public override DynamicMetaObject BindGetMember(GetMemberBinder binder)
+            {
+                var typeOf = proxy.GetTypeOfProperty(binder.Name);
+                switch (typeOf)
+                {
+                    case "undefined":
+                    case "null":
+                        return new DynamicMetaObject(Expression.Constant(null), Restrictions);
+                    case "string":
+                        var str = proxy.GetPropertyAsString(binder.Name);
+                        return new DynamicMetaObject(Expression.Constant(str), Restrictions);
+                    case "number":
+                        var num = proxy.GetPropertyAsDouble(binder.Name);
+                        return new DynamicMetaObject(Expression.Constant(num), Restrictions);
+                    case "object":
+                        var obj = proxy.GetPropertyAsJSObject(binder.Name)!;
+                        return new MetaDynamic(Expression.Constant(obj), obj);
+                    case "function":
+                    default:
+                        throw new NotImplementedException(typeOf);
+                }
+            }
+        }
+    }
+}

src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportExportTest.cs

@@ -31,6 +31,27 @@ public async Task MultipleImportAsync()
             Assert.Same(instance1, instance2);
         }
 
+        [Fact]
+        public async Task Dynamic()
+        {
+            dynamic globalThis = JSHost.GlobalThis;
+            Console.WriteLine("Hello from " + globalThis.os?.d8Path);
+            Console.WriteLine("Hello from " + globalThis.location?.href);
+
+            var first = await JSHost.ImportAsync("JavaScriptTestHelper", "./JavaScriptTestHelper.mjs");
+            Assert.NotNull(first);
+            dynamic instance1 = first.GetPropertyAsJSObject("instance");
+
+            //Assert.Null((object)instance1.missing);
+            //Assert.Null((object)instance1.nnn);
+            Assert.Equal("xxx", (string)instance1.xxx);
+            var yyy = instance1.yyy;
+            Assert.IsType<JSObject>(yyy);
+            //double zzz = yyy.zzz;
+            //Assert.Equal(3.14d, (double)zzz);
+        }
+
+
         [Fact]
         public unsafe void GlobalThis()
         {

src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.mjs

@@ -363,7 +363,13 @@ export function backback(arg1, arg2, arg3) {
     }
 }
 
-export const instance = {}
+export const instance = {
+    nnn:null,
+    xxx:"xxx",
+    yyy:{
+        zzz:3.14
+    }
+}
 
 globalThis.javaScriptTestHelper = instance;
 globalThis.data = new JSData("i-n-s-t-a-n-c-e");