From 8c9e544b0d4c21562321d3dd4f46a65889e89c90 Mon Sep 17 00:00:00 2001
From: Radek Doulik <radek.doulik@gmail.com>
Date: Mon, 26 Oct 2026 21:08:54 +0100
Subject: [PATCH 1/2] [wasm][coreclr] Default browser R2R publishing to
 composite

Preserve per-assembly opt-outs across consumer and in-tree builds, including nested sample publishes.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 519ad6c4-3702-45c6-bb99-0e2ad8573d04
---
 .../testing/libraries/testing-wasm.md         | 28 +++++++++++--------
 src/mono/browser/build/WasmApp.InTree.props   |  2 ++
 ...bAssembly.Browser.CoreCLR.Defaults.targets | 14 ++++++++++
 ...ET.Sdk.WebAssembly.Browser.CoreCLR.targets |  6 ++--
 ...icrosoft.NET.Sdk.WebAssembly.Browser.props |  3 ++
 src/mono/sample/wasm/Directory.Build.props    |  1 +
 src/mono/sample/wasm/Directory.Build.targets  |  1 +
 .../Wasm.Build.Tests/NativeLibraryTests.cs    |  2 +-
 .../wasm/Wasm.Build.Tests/ReadyToRunTests.cs  |  3 +-
 9 files changed, 42 insertions(+), 18 deletions(-)
 create mode 100644 src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets

diff --git a/docs/workflow/testing/libraries/testing-wasm.md b/docs/workflow/testing/libraries/testing-wasm.md
index 557a85c7c7d27f..6969c5e83600e2 100644
--- a/docs/workflow/testing/libraries/testing-wasm.md
+++ b/docs/workflow/testing/libraries/testing-wasm.md
@@ -194,26 +194,30 @@ stale staged assets can otherwise cause assembly-loading failures before tests s
 The `LibraryTestsCoreCLR_R2R` CI jobs use the same configuration and archive the published
 tests for execution on Helix. The existing interpreter jobs remain separate.
 
-To run a library suite with a single composite ReadyToRun image instead of per-assembly
-images, add `PublishReadyToRunComposite=true`:
+CoreCLR browser ReadyToRun tests publish a single composite image
+(`<test assembly>.r2r.wasm`) by default. It is staged into `wwwroot/_framework` beside
+the component WebCIL stubs and listed in the boot config.
+
+To run a library suite with per-assembly ReadyToRun images instead, add
+`PublishReadyToRunComposite=false`:
 
 ```bash
 XHARNESS_COMMAND=test-browser ./build.sh libs.tests -test -os browser -c Release \
   --projects $PWD/src/libraries/System.Memory/tests/System.Memory.Tests.csproj \
-  /p:RuntimeFlavor=CoreCLR /p:TestWasmReadyToRun=true /p:PublishReadyToRunComposite=true \
+  /p:RuntimeFlavor=CoreCLR /p:TestWasmReadyToRun=true /p:PublishReadyToRunComposite=false \
   /p:EnableAggressiveTrimming=true /p:Scenario=WasmTestOnChrome /p:InstallChromeForTests=true
 ```
 
-The composite image (`<test assembly>.r2r.wasm`) is staged into `wwwroot/_framework` beside
-the component WebCIL stubs and listed in the boot config. As with other mode switches, clean
-the project-specific `bin` and `obj` outputs when switching between composite and per-assembly
-images.
+As with other mode switches, clean the project-specific `bin` and `obj` outputs when
+switching between composite and per-assembly images.
 
-For CoreCLR browser applications, set `PublishReadyToRun=true` and
-`PublishReadyToRunComposite=true` to publish a single composite ReadyToRun image and
-component WebCIL stubs instead of per-assembly images. Publishing requires a wasm-capable
-crossgen2 and WebCIL enabled; the composite is loaded before the runtime starts.
-`ReadyToRunTests.PublishRunAllPagesComposite` exercises trimmed, untrimmed, and
+For CoreCLR browser applications, ReadyToRun remains opt-in: set
+`PublishReadyToRun=true` to publish a single composite ReadyToRun image and component
+WebCIL stubs. Set `PublishReadyToRunComposite=false` to retain per-assembly images.
+Publishing requires a wasm-capable crossgen2. Composite publishing additionally requires
+ReadyToRun SDK tasks that support wasm composite output naming and WebCIL enabled;
+the composite is loaded before the runtime starts.
+`ReadyToRunTests.PublishRunAllPagesComposite` exercises the default mode with trimmed, untrimmed, and
 native-relinked publishes in a browser, including asset fingerprinting when
 `USE_FINGERPRINTING_FOR_TESTS=true`.
 
diff --git a/src/mono/browser/build/WasmApp.InTree.props b/src/mono/browser/build/WasmApp.InTree.props
index 2eb17ec0c0f94c..4634f534918b3e 100644
--- a/src/mono/browser/build/WasmApp.InTree.props
+++ b/src/mono/browser/build/WasmApp.InTree.props
@@ -17,6 +17,8 @@
 
   <PropertyGroup Condition="'$(RuntimeFlavor)' == 'CoreCLR'">
     <UseMonoRuntime>false</UseMonoRuntime>
+    <!-- Library tests import these props after the SDK's early-defaults hook has run. -->
+    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">true</PublishReadyToRunComposite>
     <!-- TODO-WASM https://github.com/dotnet/runtime/issues/120226 (CoreCLR on wasm defaults) -->
     <InvariantGlobalization Condition="'$(InvariantGlobalization)' == ''">false</InvariantGlobalization>
   </PropertyGroup>
diff --git a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
new file mode 100644
index 00000000000000..57b8aeaea309d3
--- /dev/null
+++ b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
@@ -0,0 +1,14 @@
+<!--
+***********************************************************************************************
+Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
+
+CoreCLR browser-wasm defaults applied before Microsoft.NET.Sdk targets.
+
+Copyright (c) .NET Foundation. All rights reserved.
+***********************************************************************************************
+-->
+<Project>
+  <PropertyGroup Condition="'$(UseMonoRuntime)' == 'false'">
+    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">true</PublishReadyToRunComposite>
+  </PropertyGroup>
+</Project>
diff --git a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.targets b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.targets
index 3c08f87116f957..ff459ebc3a15a2 100644
--- a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.targets
+++ b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.targets
@@ -21,8 +21,6 @@ Copyright (c) .NET Foundation. All rights reserved.
     <!-- Override only the incompatible SDK default: net11+ defaults ContainerFormat=pe (unloadable on wasm).
          An explicit unsupported value is left as-is and rejected by _WasmCoreClrValidateReadyToRun. -->
     <PublishReadyToRunContainerFormat Condition="'$(PublishReadyToRunContainerFormat)' == '' or '$(PublishReadyToRunContainerFormat)' == 'pe'">wasm</PublishReadyToRunContainerFormat>
-    <!-- Keep the existing per-assembly behavior unless composite is explicitly requested. -->
-    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">false</PublishReadyToRunComposite>
     <!-- Compile every assembly into one shared (large) version bubble. -->
     <PublishReadyToRunCrossgen2ExtraArgs>$(PublishReadyToRunCrossgen2ExtraArgs);--opt-cross-module:*</PublishReadyToRunCrossgen2ExtraArgs>
   </PropertyGroup>
@@ -56,7 +54,7 @@ Copyright (c) .NET Foundation. All rights reserved.
           Condition="'$(PublishReadyToRun)' == 'true'"
           BeforeTargets="_WasmCoreClrSelectR2RDirectories;_ResolveWasmOutputs">
     <Error Condition="'$(PublishReadyToRunComposite)' == 'true' and '$(_WasmEnableWebcil)' != 'true'"
-           Text="PublishReadyToRunComposite for CoreCLR browser-wasm requires WebCIL-in-Wasm assemblies; enable WasmEnableWebcil." />
+           Text="PublishReadyToRunComposite for CoreCLR browser-wasm requires WebCIL-in-Wasm assemblies; enable WasmEnableWebcil. To opt out of composite mode, set PublishReadyToRunComposite=false." />
     <Error Condition="'$(PublishReadyToRunContainerFormat)' != 'wasm'"
            Text="PublishReadyToRunContainerFormat '$(PublishReadyToRunContainerFormat)' is not supported for CoreCLR browser-wasm; only 'wasm' is supported." />
     <!-- CPU sampling observes only interpreted frames, so R2R (native wasm) methods are missing from traces until #130521. -->
@@ -77,7 +75,7 @@ Copyright (c) .NET Foundation. All rights reserved.
       <_WasmCompositeOwnerEntry Include="@(_ReadyToRunCompileList->WithMetadataValue('CreateCompositeImage', 'true'))" />
     </ItemGroup>
     <Error Condition="'@(_WasmCompositeOwnerEntry)' != '' and !$([System.String]::Copy('%(_WasmCompositeOwnerEntry.OutputR2RImage)').EndsWith('.r2r.wasm'))"
-           Text="PublishReadyToRunComposite for CoreCLR browser-wasm requires ReadyToRun SDK tasks that name the composite image '&lt;entry&gt;.r2r.wasm', but they planned '$([System.IO.Path]::GetFileName('%(_WasmCompositeOwnerEntry.OutputR2RImage)'))'. Use an SDK with wasm ReadyToRun output naming (dotnet/sdk#56395), or set Crossgen2SdkOverridePropsPath and Crossgen2SdkOverrideTargetsPath to the dotnet/runtime Crossgen2Tasks." />
+           Text="PublishReadyToRunComposite for CoreCLR browser-wasm requires ReadyToRun SDK tasks that name the composite image '&lt;entry&gt;.r2r.wasm', but they planned '$([System.IO.Path]::GetFileName('%(_WasmCompositeOwnerEntry.OutputR2RImage)'))'. Use an SDK with wasm ReadyToRun output naming (dotnet/sdk#56395), or set Crossgen2SdkOverridePropsPath and Crossgen2SdkOverrideTargetsPath to the dotnet/runtime Crossgen2Tasks. To opt out of composite mode, set PublishReadyToRunComposite=false." />
   </Target>
 
   <!-- PublishTrimmed selects the staged closure (untrimmed pack vs linker output) exactly like
diff --git a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
index 902c930716bcf8..eece829596ecb3 100644
--- a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
+++ b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
@@ -38,6 +38,9 @@ Copyright (c) .NET Foundation. All rights reserved.
     <StaticWebAssetsAdditionalPublishPropertiesToRemove>$(StaticWebAssetsAdditionalPublishPropertiesToRemove);NoBuild;RuntimeIdentifier</StaticWebAssetsAdditionalPublishPropertiesToRemove>
     <StaticWebAssetStandaloneHosting Condition="'$(StaticWebAssetStandaloneHosting)' == '' and '$(StaticWebAssetProjectMode)' == 'Root'">true</StaticWebAssetStandaloneHosting>
     <StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute Condition="'$(StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute)' == ''">true</StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute>
+
+    <!-- Apply CoreCLR defaults after project properties but before the SDK defaults R2R to per-assembly. -->
+    <BeforeMicrosoftNETSdkTargets>$(BeforeMicrosoftNETSdkTargets);$(MSBuildThisFileDirectory)Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets</BeforeMicrosoftNETSdkTargets>
   </PropertyGroup>
 
   <!-- CoreCLR browser-wasm ReadyToRun wiring, isolated from Mono; active only with an in-build crossgen2.
diff --git a/src/mono/sample/wasm/Directory.Build.props b/src/mono/sample/wasm/Directory.Build.props
index b63362260ba5e2..03138cf9ff35a0 100644
--- a/src/mono/sample/wasm/Directory.Build.props
+++ b/src/mono/sample/wasm/Directory.Build.props
@@ -53,6 +53,7 @@
   <PropertyGroup>
     <RuntimeFlavor Condition="'$(Nested_RuntimeFlavor)' != ''">$(Nested_RuntimeFlavor)</RuntimeFlavor>
     <PublishReadyToRun Condition="'$(PublishReadyToRun)' == '' and '$(Nested_PublishReadyToRun)' != ''">$(Nested_PublishReadyToRun)</PublishReadyToRun>
+    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == '' and '$(Nested_PublishReadyToRunComposite)' != ''">$(Nested_PublishReadyToRunComposite)</PublishReadyToRunComposite>
     <PublishReadyToRun Condition="'$(PublishReadyToRun)' == ''">false</PublishReadyToRun>
   </PropertyGroup>
 
diff --git a/src/mono/sample/wasm/Directory.Build.targets b/src/mono/sample/wasm/Directory.Build.targets
index bd4f2de1aa2de6..e7f33cf2022e0a 100644
--- a/src/mono/sample/wasm/Directory.Build.targets
+++ b/src/mono/sample/wasm/Directory.Build.targets
@@ -34,6 +34,7 @@
     <NestedBuildProperty Include="InvariantTimezone" />
     <NestedBuildProperty Include="PublishTrimmed" />
     <NestedBuildProperty Include="PublishReadyToRun" />
+    <NestedBuildProperty Include="PublishReadyToRunComposite" />
     <NestedBuildProperty Include="RunAOTCompilation" />
     <NestedBuildProperty Include="UsingNativeAOT" />
     <NestedBuildProperty Include="WasmBuildNative" />
diff --git a/src/mono/wasm/Wasm.Build.Tests/NativeLibraryTests.cs b/src/mono/wasm/Wasm.Build.Tests/NativeLibraryTests.cs
index 21307e7197e75b..62a102cc0e5e1a 100644
--- a/src/mono/wasm/Wasm.Build.Tests/NativeLibraryTests.cs
+++ b/src/mono/wasm/Wasm.Build.Tests/NativeLibraryTests.cs
@@ -41,7 +41,7 @@ private async Task ProjectWithNativeReferenceCore(Configuration config, bool aot
             string extraItems = $"<NativeFileReference Include=\"{objectFilename}\" />";
             string extraProperties = "<WasmBuildNative>true</WasmBuildNative>";
             if (readyToRun)
-                extraProperties += "<PublishReadyToRun>true</PublishReadyToRun>";
+                extraProperties += "<PublishReadyToRun>true</PublishReadyToRun><PublishReadyToRunComposite>false</PublishReadyToRunComposite>";
             string insertAtEnd = readyToRun
                 ? """
                     <Target Name="PrintReadyToRunPInvokeModules" AfterTargets="_WasmConfigureReadyToRunPInvokes">
diff --git a/src/mono/wasm/Wasm.Build.Tests/ReadyToRunTests.cs b/src/mono/wasm/Wasm.Build.Tests/ReadyToRunTests.cs
index 84f705655670cd..1a75b5de7fe501 100644
--- a/src/mono/wasm/Wasm.Build.Tests/ReadyToRunTests.cs
+++ b/src/mono/wasm/Wasm.Build.Tests/ReadyToRunTests.cs
@@ -82,8 +82,9 @@ private async Task PublishRunAllPagesCore(Configuration config, bool trimmed, bo
             string extraItems = composite
                 ? """<ProjectReference Include="../R2rSuffixLibrary/R2rSuffixLibrary.csproj" />"""
                 : string.Empty;
+            string compositeProperty = composite ? string.Empty : "<PublishReadyToRunComposite>false</PublishReadyToRunComposite>";
             ProjectInfo info = CopyTestAsset(config, aot: false, TestAsset.BlazorBasicTestApp, label,
-                extraProperties: $"<PublishReadyToRun>true</PublishReadyToRun><PublishReadyToRunComposite>{(composite ? "true" : "false")}</PublishReadyToRunComposite><PublishTrimmed>{(trimmed ? "true" : "false")}</PublishTrimmed>",
+                extraProperties: $"<PublishReadyToRun>true</PublishReadyToRun>{compositeProperty}<PublishTrimmed>{(trimmed ? "true" : "false")}</PublishTrimmed>",
                 extraItems: extraItems);
             if (composite)
                 LogR2RSuffixLibraryMarker();

From 6493669cb10554aeedf4a221155387fae2dc5a09 Mon Sep 17 00:00:00 2001
From: Radek Doulik <radek.doulik@gmail.com>
Date: Tue, 3 Nov 2026 16:41:06 +0100
Subject: [PATCH 2/2] [wasm] Simplify composite ReadyToRun default

Set PublishReadyToRunComposite directly in browser props whenever it is unset, without depending on runtime selection. Remove the early-target import, separate defaults file, and duplicate in-tree assignment.

Preserve explicit overrides and keep ReadyToRun itself opt-in.

Co-authored-by: Copilot App <223556219+Copilot@users.noreply.github.com>
Copilot-Session: 519ad6c4-3702-45c6-bb99-0e2ad8573d04
---
 src/mono/browser/build/WasmApp.InTree.props        |  2 --
 ...dk.WebAssembly.Browser.CoreCLR.Defaults.targets | 14 --------------
 .../Microsoft.NET.Sdk.WebAssembly.Browser.props    |  5 ++---
 3 files changed, 2 insertions(+), 19 deletions(-)
 delete mode 100644 src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets

diff --git a/src/mono/browser/build/WasmApp.InTree.props b/src/mono/browser/build/WasmApp.InTree.props
index 4634f534918b3e..2eb17ec0c0f94c 100644
--- a/src/mono/browser/build/WasmApp.InTree.props
+++ b/src/mono/browser/build/WasmApp.InTree.props
@@ -17,8 +17,6 @@
 
   <PropertyGroup Condition="'$(RuntimeFlavor)' == 'CoreCLR'">
     <UseMonoRuntime>false</UseMonoRuntime>
-    <!-- Library tests import these props after the SDK's early-defaults hook has run. -->
-    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">true</PublishReadyToRunComposite>
     <!-- TODO-WASM https://github.com/dotnet/runtime/issues/120226 (CoreCLR on wasm defaults) -->
     <InvariantGlobalization Condition="'$(InvariantGlobalization)' == ''">false</InvariantGlobalization>
   </PropertyGroup>
diff --git a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
deleted file mode 100644
index 57b8aeaea309d3..00000000000000
--- a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
+++ /dev/null
@@ -1,14 +0,0 @@
-<!--
-***********************************************************************************************
-Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets
-
-CoreCLR browser-wasm defaults applied before Microsoft.NET.Sdk targets.
-
-Copyright (c) .NET Foundation. All rights reserved.
-***********************************************************************************************
--->
-<Project>
-  <PropertyGroup Condition="'$(UseMonoRuntime)' == 'false'">
-    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">true</PublishReadyToRunComposite>
-  </PropertyGroup>
-</Project>
diff --git a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
index 2fcdc42126407b..3b44a521a85a16 100644
--- a/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
+++ b/src/mono/nuget/Microsoft.NET.Sdk.WebAssembly.Pack/build/Microsoft.NET.Sdk.WebAssembly.Browser.props
@@ -24,6 +24,8 @@ Copyright (c) .NET Foundation. All rights reserved.
     <!-- Turn off symbol publishing by default -->
     <CopyOutputSymbolsToPublishDirectory>false</CopyOutputSymbolsToPublishDirectory>
 
+    <PublishReadyToRunComposite Condition="'$(PublishReadyToRunComposite)' == ''">true</PublishReadyToRunComposite>
+
     <!-- Trimmer defaults -->
     <TrimMode Condition="'$(TrimMode)' == '' and '$(UsingMicrosoftNETSdkBlazorWebAssembly)' == 'true'">partial</TrimMode>
     <TrimMode Condition="'$(TrimMode)' == '' and '$(UsingMicrosoftNETSdkBlazorWebAssembly)' != 'true'">full</TrimMode>
@@ -38,9 +40,6 @@ Copyright (c) .NET Foundation. All rights reserved.
     <StaticWebAssetsAdditionalPublishPropertiesToRemove>$(StaticWebAssetsAdditionalPublishPropertiesToRemove);NoBuild;RuntimeIdentifier</StaticWebAssetsAdditionalPublishPropertiesToRemove>
     <StaticWebAssetStandaloneHosting Condition="'$(StaticWebAssetStandaloneHosting)' == '' and '$(StaticWebAssetProjectMode)' == 'Root'">true</StaticWebAssetStandaloneHosting>
     <StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute Condition="'$(StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute)' == ''">true</StaticWebAssetMakeReferencedAssetOriginalItemSpecAbsolute>
-
-    <!-- Apply CoreCLR defaults after project properties but before the SDK defaults R2R to per-assembly. -->
-    <BeforeMicrosoftNETSdkTargets>$(BeforeMicrosoftNETSdkTargets);$(MSBuildThisFileDirectory)Microsoft.NET.Sdk.WebAssembly.Browser.CoreCLR.Defaults.targets</BeforeMicrosoftNETSdkTargets>
   </PropertyGroup>
 
   <!-- Import the optional in-build crossgen2 task shim before appending the wasm ReadyToRun override.