[browser] legacy JS interop optional via WasmEnableLegacyJsInterop - …

…managed (#82826) * WasmEnableLegacyJsInterop and ILLink.Descriptors.LegacyJsInterop.xml * revert back to USE_PTHREADS symbol * feedback
dotnet · Mar 8, 2023 · 6c836e8 · 6c836e8
1 parent ceb2344
commit 6c836e8
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Showing 21 changed files with 99 additions and 37 deletions.
diff --git a/eng/testing/tests.browser.targets b/eng/testing/tests.browser.targets
@@ -30,6 +30,7 @@
 
     <GetNuGetsToBuildForWorkloadTestingDependsOn>_GetRuntimePackNuGetsToBuild;_GetNugetsForAOT;$(GetNuGetsToBuildForWorkloadTestingDependsOn)</GetNuGetsToBuildForWorkloadTestingDependsOn>
     <_BundleAOTTestWasmAppForHelixDependsOn>$(_BundleAOTTestWasmAppForHelixDependsOn);PrepareForWasmBuildApp;_PrepareForAOTOnHelix</_BundleAOTTestWasmAppForHelixDependsOn>
+    <WasmEnableLegacyJsInterop Condition="'$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
   </PropertyGroup>
 
   <!-- We expect WASM users to indicate they would like to have bigger download size by adding WasmIncludeFullIcuData, -->
@@ -126,6 +127,11 @@
   <PropertyGroup Condition="'$(BuildAOTTestsOnHelix)' == 'true'">
     <!-- wasm targets are not imported at all, in this case, because we run the wasm build on helix -->
   </PropertyGroup>
+  <ItemGroup Condition="'$(BuildAOTTestsOn)' == 'helix'">
+    <TrimmerRootDescriptor
+      Condition="'$(WasmEnableLegacyJsInterop)' == 'true'"
+      Include="$(MonoProjectRoot)\wasm\build\ILLink.Descriptors.LegacyJsInterop.xml" />
+  </ItemGroup>
 
   <PropertyGroup Condition="'$(IsWasmProject)' == 'true' and '$(BuildAOTTestsOnHelix)' != 'true'">
     <WasmBuildOnlyAfterPublish>true</WasmBuildOnlyAfterPublish>

diff --git a/src/installer/pkg/sfx/Microsoft.NETCore.App/Directory.Build.props b/src/installer/pkg/sfx/Microsoft.NETCore.App/Directory.Build.props
@@ -252,6 +252,7 @@
     <PlatformManifestFileEntry Include="emcc-props.json" IsNative="true" />
     <PlatformManifestFileEntry Include="ILLink.Substitutions.WasmIntrinsics.xml" IsNative="true" />
     <PlatformManifestFileEntry Include="ILLink.Substitutions.NoWasmIntrinsics.xml" IsNative="true" />
+    <PlatformManifestFileEntry Include="ILLink.Descriptors.LegacyJsInterop.xml" IsNative="true" />
     <!-- wasi specific -->
     <PlatformManifestFileEntry Include="main.c" IsNative="true" />
     <PlatformManifestFileEntry Include="driver.h" IsNative="true" />

diff --git a/...m.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj b/...m.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj
@@ -2,15 +2,20 @@
   <PropertyGroup>
     <TargetFrameworks>$(NetCoreAppCurrent)-browser;$(NetCoreAppCurrent)</TargetFrameworks>
     <AllowUnsafeBlocks>true</AllowUnsafeBlocks>
-    <FeatureWasmThreads Condition="'$(TargetOS)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
-    <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'" >$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
     <EnableAOTAnalyzer>false</EnableAOTAnalyzer>
   </PropertyGroup>
 
   <!-- DesignTimeBuild requires all the TargetFramework Derived Properties to not be present in the first property group. -->
   <PropertyGroup>
     <TargetPlatformIdentifier>$([MSBuild]::GetTargetPlatformIdentifier('$(TargetFramework)'))</TargetPlatformIdentifier>
     <GeneratePlatformNotSupportedAssemblyMessage Condition="'$(TargetPlatformIdentifier)' != 'browser'">SR.SystemRuntimeInteropServicesJavaScript_PlatformNotSupported</GeneratePlatformNotSupportedAssemblyMessage>
+    <FeatureWasmThreads Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(MonoWasmBuildVariant)' == 'multithread'">true</FeatureWasmThreads>
+    <WasmEnableLegacyJsInterop Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
+    <DefineConstants Condition="'$(FeatureWasmThreads)' == 'true'" >$(DefineConstants);FEATURE_WASM_THREADS</DefineConstants>
+    <DefineConstants Condition="'$(WasmEnableLegacyJsInterop)' == 'true'" >$(DefineConstants);ENABLE_LEGACY_JS_INTEROP</DefineConstants>
+    <ILLinkDescriptorsLibraryBuildXml
+      Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableLegacyJsInterop)' == 'true'"
+      >$(MonoProjectRoot)wasm\build\ILLink.Descriptors.LegacyJsInterop.xml</ILLinkDescriptorsLibraryBuildXml>
   </PropertyGroup>
 
   <ItemGroup>
@@ -22,15 +27,6 @@
     <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\JavaScriptImports.Generated.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\JavaScriptExports.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\JavaScriptImports.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\LegacyExports.cs" />
-
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Runtime.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Array.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\ArrayBuffer.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\DataView.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Function.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Uint8Array.cs" />
-    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\LegacyHostImplementation.cs" />
 
     <Compile Include="System\Runtime\InteropServices\JavaScript\JSHost.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\JSMarshalerType.cs" />
@@ -69,6 +65,18 @@
     <Compile Include="System\Runtime\InteropServices\JavaScript\JSSynchronizationContext.cs" />
   </ItemGroup>
 
+  <!-- only include legacy interop when WasmEnableLegacyJsInterop is enabled -->
+  <ItemGroup Condition="'$(TargetPlatformIdentifier)' == 'browser' and '$(WasmEnableLegacyJsInterop)' == 'true'">
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Interop\LegacyExports.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Runtime.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Array.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\ArrayBuffer.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\DataView.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Function.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\Uint8Array.cs" />
+    <Compile Include="System\Runtime\InteropServices\JavaScript\Legacy\LegacyHostImplementation.cs" />
+  </ItemGroup>
+
   <ItemGroup>
     <Reference Include="System.Collections" />
     <Reference Include="System.Memory" />

diff --git a/...ces.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.cs b/...ces.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptImports.cs
@@ -20,6 +20,7 @@ public static void MarshalPromise(Span<JSMarshalerArgument> arguments)
             }
         }
 
+#if ENABLE_LEGACY_JS_INTEROP
         #region legacy
 
         public static object GetGlobalObject(string? str = null)
@@ -30,7 +31,7 @@ public static object GetGlobalObject(string? str = null)
             if (exception != 0)
                 throw new JSException(SR.Format(SR.ErrorResolvingFromGlobalThis, str));
 
-            JSHostImplementation.ReleaseInFlight(jsObj);
+            LegacyHostImplementation.ReleaseInFlight(jsObj);
             return jsObj;
         }
 
@@ -44,5 +45,6 @@ public static IntPtr CreateCSOwnedObject(string typeName, object[] parms)
         }
 
         #endregion
+#endif
     }
 }
diff --git a/...ervices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/LegacyExports.cs b/...ervices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/LegacyExports.cs
@@ -9,8 +9,7 @@
 
 namespace System.Runtime.InteropServices.JavaScript
 {
-    // this maps to src\mono\wasm\runtime\legacy\corebindings.ts
-    // the public methods are protected from trimming by DynamicDependency on JSFunctionBinding.BindJSFunction
+    // the public methods are protected from trimming by ILLink.Descriptors.LegacyJsInterop.xml
     internal static unsafe partial class LegacyExports
     {
         public static void GetCSOwnedObjectByJSHandleRef(nint jsHandle, int shouldAddInflight, out JSObject? result)

diff --git a/...ropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSFunctionBinding.cs b/...ropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSFunctionBinding.cs
@@ -142,8 +142,6 @@ public static void InvokeJS(JSFunctionBinding signature, Span<JSMarshalerArgumen
         /// <exception cref="PlatformNotSupportedException">The method is executed on an architecture other than WebAssembly.</exception>
         // JavaScriptExports need to be protected from trimming because they are used from C/JS code which IL linker can't see
         [DynamicDependency(DynamicallyAccessedMemberTypes.PublicMethods, "System.Runtime.InteropServices.JavaScript.JavaScriptExports", "System.Runtime.InteropServices.JavaScript")]
-        // TODO make this DynamicDependency conditional
-        [DynamicDependency(DynamicallyAccessedMemberTypes.PublicMethods, "System.Runtime.InteropServices.JavaScript.LegacyExports", "System.Runtime.InteropServices.JavaScript")]
         public static JSFunctionBinding BindJSFunction(string functionName, string moduleName, ReadOnlySpan<JSMarshalerType> signatures)
         {
             if (RuntimeInformation.OSArchitecture != Architecture.Wasm)

diff --git a/...Services.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.cs b/...Services.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.cs
@@ -42,13 +42,6 @@ public static void ReleaseCSOwnedObject(nint jsHandle)
             throw new InvalidOperationException();
         }
 
-        [MethodImpl(MethodImplOptions.AggressiveInlining)]
-        public static void ReleaseInFlight(object obj)
-        {
-            JSObject? jsObj = obj as JSObject;
-            jsObj?.ReleaseInFlight();
-        }
-
         // A JSOwnedObject is a managed object with its lifetime controlled by javascript.
         // The managed side maintains a strong reference to the object, while the JS side
         //  maintains a weak reference and notifies the managed side if the JS wrapper object

diff --git a/...pServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSObject.References.cs b/...pServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSObject.References.cs
@@ -10,17 +10,18 @@ public partial class JSObject
     {
         internal nint JSHandle;
 
+#if ENABLE_LEGACY_JS_INTEROP
         internal GCHandle? InFlight;
         internal int InFlightCounter;
+#endif
         private bool _isDisposed;
 
         internal JSObject(IntPtr jsHandle)
         {
             JSHandle = jsHandle;
-            InFlight = null;
-            InFlightCounter = 0;
         }
 
+#if ENABLE_LEGACY_JS_INTEROP
         internal void AddInFlight()
         {
             ObjectDisposedException.ThrowIf(IsDisposed, this);
@@ -53,6 +54,7 @@ internal void ReleaseInFlight()
                 }
             }
         }
+#endif
 
         /// <inheritdoc />
         public override bool Equals([NotNullWhen(true)] object? obj) => obj is JSObject other && JSHandle == other.JSHandle;

diff --git a/....InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/Array.cs b/....InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/Array.cs
@@ -91,7 +91,7 @@ public object this[int i]
 
                 if (exception != 0)
                     throw new JSException((string)indexValue);
-                JSHostImplementation.ReleaseInFlight(indexValue);
+                LegacyHostImplementation.ReleaseInFlight(indexValue);
                 return indexValue;
             }
             set

diff --git a/...vaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/LegacyHostImplementation.cs b/...vaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/LegacyHostImplementation.cs
@@ -10,6 +10,13 @@ namespace System.Runtime.InteropServices.JavaScript
     [SupportedOSPlatform("browser")]
     internal static class LegacyHostImplementation
     {
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public static void ReleaseInFlight(object obj)
+        {
+            JSObject? jsObj = obj as JSObject;
+            jsObj?.ReleaseInFlight();
+        }
+
         [MethodImpl(MethodImplOptions.AggressiveInlining)]
         public static void RegisterCSOwnedObject(JSObject proxy)
         {

diff --git a/...nteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/Runtime.cs b/...nteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Legacy/Runtime.cs
@@ -39,7 +39,7 @@ public static object Invoke(this JSObject self, string method, params object?[]
             Interop.Runtime.InvokeJSWithArgsRef(self.JSHandle, method, args, out int exception, out object res);
             if (exception != 0)
                 throw new JSException((string)res);
-            JSHostImplementation.ReleaseInFlight(res);
+            LegacyHostImplementation.ReleaseInFlight(res);
             return res;
         }
 
@@ -74,7 +74,7 @@ public static object GetObjectProperty(this JSObject self, string name)
             Interop.Runtime.GetObjectPropertyRef(self.JSHandle, name, out int exception, out object propertyValue);
             if (exception != 0)
                 throw new JSException((string)propertyValue);
-            JSHostImplementation.ReleaseInFlight(propertyValue);
+            LegacyHostImplementation.ReleaseInFlight(propertyValue);
             return propertyValue;
         }
 

diff --git a/...Script.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj b/...Script.Legacy.UnitTests/System.Runtime.InteropServices.JavaScript.Legacy.UnitTests.csproj
@@ -5,8 +5,11 @@
     <TestRuntime>true</TestRuntime>
     <WasmXHarnessArgs>$(WasmXHarnessArgs) --engine-arg=--expose-gc --web-server-use-cop</WasmXHarnessArgs>
     <NoWarn>0612</NoWarn>
+    <WasmEnableLegacyJsInterop Condition="'$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
+    <DefineConstants Condition="'$(WasmEnableLegacyJsInterop)' == 'true'">$(DefineConstants);ENABLE_LEGACY_JS_INTEROP</DefineConstants>
   </PropertyGroup>
-  <ItemGroup>
+
+  <ItemGroup Condition="'$(WasmEnableLegacyJsInterop)' == 'true'">
     <Compile Include="System\Runtime\InteropServices\JavaScript\JavaScriptTests.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\DataViewTests.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\MemoryTests.cs" />
@@ -16,9 +19,12 @@
     <Compile Include="System\Runtime\InteropServices\JavaScript\DelegateTests.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\HelperMarshal.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\Http\HttpRequestMessageTest.cs" />
+    <Compile Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\tests\System.Runtime.InteropServices.JavaScript.UnitTests\System\Runtime\InteropServices\JavaScript\Utils.cs" Link="System\Runtime\InteropServices\JavaScript\Utils.cs" />
+  </ItemGroup>
+
+  <ItemGroup>
     <Compile Include="System\Runtime\InteropServices\JavaScript\ParallelTests.cs" />
     <Compile Include="System\Runtime\InteropServices\JavaScript\TimerTests.cs" />
-    <Compile Include="$(LibrariesProjectRoot)System.Runtime.InteropServices.JavaScript\tests\System.Runtime.InteropServices.JavaScript.UnitTests\System\Runtime\InteropServices\JavaScript\Utils.cs" Link="System\Runtime\InteropServices\JavaScript\Utils.cs" />
   </ItemGroup>
 
   <ItemGroup>

diff --git a/...teropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj b/...teropServices.JavaScript.UnitTests/System.Runtime.InteropServices.JavaScript.Tests.csproj
@@ -4,6 +4,8 @@
     <TargetFrameworks>$(NetCoreAppCurrent)-browser</TargetFrameworks>
     <TestRuntime>true</TestRuntime>
     <WasmXHarnessArgs>$(WasmXHarnessArgs) --engine-arg=--expose-gc --web-server-use-cop</WasmXHarnessArgs>
+    <WasmEnableLegacyJsInterop Condition="'$(WasmEnableLegacyJsInterop)' == ''">true</WasmEnableLegacyJsInterop>
+    <DefineConstants Condition="'$(WasmEnableLegacyJsInterop)' == 'true'">$(DefineConstants);ENABLE_LEGACY_JS_INTEROP</DefineConstants>
     <!-- Use following lines to write the generated files to disk. -->
     <EmitCompilerGeneratedFiles>true</EmitCompilerGeneratedFiles>
   </PropertyGroup>

diff --git a/...ices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportExportTest.cs b/...ices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportExportTest.cs
@@ -58,8 +58,10 @@ public unsafe void GlobalThis()
         [Fact]
         public unsafe void DotnetInstance()
         {
+#if ENABLE_LEGACY_JS_INTEROP
             Assert.True(JSHost.DotnetInstance.HasProperty("MONO"));
             Assert.Equal("object", JSHost.DotnetInstance.GetTypeOfProperty("MONO"));
+#endif
 
             JSHost.DotnetInstance.SetProperty("testBool", true);
             Assert.Equal("boolean", JSHost.DotnetInstance.GetTypeOfProperty("testBool"));

diff --git a/...nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/Microsoft.NET.Runtime.WebAssembly.Sdk.pkgproj b/...nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/Microsoft.NET.Runtime.WebAssembly.Sdk.pkgproj
@@ -13,6 +13,7 @@
     <PackageFile Include="Sdk\AutoImport.props" TargetPath="Sdk" />
     <PackageFile Include="Sdk\Sdk.props" TargetPath="Sdk" />
     <PackageFile Include="$(RepoRoot)\src\mono\wasm\build\ILLink.Substitutions.*.xml" TargetPath="Sdk" />
+    <PackageFile Include="$(RepoRoot)\src\mono\wasm\build\ILLink.Descriptors.*.xml" TargetPath="Sdk" />
     <PackageFile Include="$(RepoRoot)\src\mono\wasm\build\WasmApp.props" TargetPath="Sdk" />
     <PackageFile Include="$(RepoRoot)\src\mono\wasm\build\WasmApp.targets" TargetPath="Sdk" />
     <PackageFile Include="$(RepoRoot)\src\mono\wasm\build\WasmApp.Native.*" TargetPath="Sdk" />

diff --git a/src/mono/wasm/build/ILLink.Descriptors.LegacyJsInterop.xml b/src/mono/wasm/build/ILLink.Descriptors.LegacyJsInterop.xml
@@ -0,0 +1,24 @@
+<linker>
+  <!-- LegacyExports need to be protected from trimming because methods are used from C/JS code which IL linker can't see -->
+  <assembly fullname="System.Runtime.InteropServices.JavaScript">
+    <type fullname="System.Runtime.InteropServices.JavaScript.LegacyExports">
+        <method name="GetCSOwnedObjectByJSHandleRef" />
+        <method name="GetCSOwnedObjectJSHandleRef" />
+        <method name="TryGetCSOwnedObjectJSHandleRef" />
+        <method name="CreateCSOwnedProxyRef" />
+        <method name="GetJSOwnedObjectByGCHandleRef" />
+        <method name="GetJSOwnedObjectGCHandleRef" />
+        <method name="CreateTaskSource" />
+        <method name="SetTaskSourceResultRef" />
+        <method name="SetTaskSourceFailure" />
+        <method name="GetTaskSourceTaskRef" />
+        <method name="SetupJSContinuationRef" />
+        <method name="ObjectToStringRef" />
+        <method name="GetDateValueRef" />
+        <method name="CreateDateTimeRef" />
+        <method name="CreateUriRef" />
+        <method name="IsSimpleArrayRef" />
+        <method name="GetCallSignatureRef" />
+    </type>
+  </assembly>
+</linker>
diff --git a/src/mono/wasm/build/WasmApp.Native.targets b/src/mono/wasm/build/WasmApp.Native.targets
@@ -258,7 +258,6 @@
       <EmscriptenEnvVars Include="PYTHONHOME=" Condition="'$(OS)' == 'Windows_NT'" />
       <EmscriptenEnvVars Include="EM_CACHE=$(WasmCachePath)" Condition="'$(WasmCachePath)' != ''" />
       <EmscriptenEnvVars Include="WasmEnableLegacyJsInterop=$(WasmEnableLegacyJsInterop)"/>
-      <EmscriptenEnvVars Include="MonoWasmThreads=$(MonoWasmThreads)"/>
     </ItemGroup>
 
     <ItemGroup Condition="'$(WasmAllowUndefinedSymbols)' == 'true'">

diff --git a/src/mono/wasm/build/WasmApp.targets b/src/mono/wasm/build/WasmApp.targets
@@ -135,6 +135,10 @@
 
     <SupportedPlatform Condition="'$(IsBrowserWasmProject)' == 'true'" Remove="@(SupportedPlatform)" />
     <SupportedPlatform Condition="'$(IsBrowserWasmProject)' == 'true'" Include="browser" />
+
+    <TrimmerRootDescriptor
+      Condition="'$(WasmEnableLegacyJsInterop)' == 'true'"
+      Include="$(MSBuildThisFileDirectory)ILLink.Descriptors.LegacyJsInterop.xml" />
   </ItemGroup>
 
   <PropertyGroup Label="Identify app bundle directory to run from">

diff --git a/src/mono/wasm/runtime/es6/dotnet.es6.lib.js b/src/mono/wasm/runtime/es6/dotnet.es6.lib.js
@@ -4,9 +4,17 @@
 
 "use strict";
 
-const monoWasmThreads = process.env.MonoWasmThreads == "true";
-const WasmEnableLegacyJsInterop = process.env.WasmEnableLegacyJsInterop === "true";
-const isPThread = monoWasmThreads ? "ENVIRONMENT_IS_PTHREAD" : "false";
+// USE_PTHREADS is emscripten's define symbol, which is passed to acorn optimizer, so we could use it here
+#if USE_PTHREADS
+const monoWasmThreads = true;
+const isPThread = `ENVIRONMENT_IS_PTHREAD`;
+#else
+const monoWasmThreads = false;
+const isPThread = "false";
+#endif
+
+// because we can't pass custom define symbols to acorn optimizer, we use environment variables to pass other build options
+const WasmEnableLegacyJsInterop = process.env.WasmEnableLegacyJsInterop !== "false";
 
 const DotnetSupportLib = {
     $DOTNET: {},

diff --git a/src/mono/wasm/runtime/net6-legacy/corebindings.ts b/src/mono/wasm/runtime/net6-legacy/corebindings.ts
@@ -88,7 +88,7 @@ export function init_legacy_exports(): void {
     legacyHelpers.runtime_legacy_exports_classname = "LegacyExports";
     legacyHelpers.runtime_legacy_exports_class = cwraps.mono_wasm_assembly_find_class(runtimeHelpers.runtime_interop_module, runtimeHelpers.runtime_interop_namespace, legacyHelpers.runtime_legacy_exports_classname);
     if (!legacyHelpers.runtime_legacy_exports_class)
-        throw "Can't find " + runtimeHelpers.runtime_interop_namespace + "." + runtimeHelpers.runtime_interop_exports_classname + " class";
+        throw "Can't find " + runtimeHelpers.runtime_interop_namespace + "." + legacyHelpers.runtime_legacy_exports_classname + " class";
 
     for (const sig of fn_signatures) {
         const wf: any = legacyManagedExports;