[WIP] Enable wasm-tools workload for CoreCLR WASM targets by lewing · Pull Request #130226 · dotnet/runtime

lewing · 2026-07-05T23:22:06Z

Summary

Prototype enabling the wasm-tools workload infrastructure for CoreCLR browser-wasm targets. This allows CoreCLR WASM apps to use the same native relinking pipeline (emcc compile/link, PInvokeTableGenerator) that Mono uses today, without bundling the Mono runtime pack or AOT compiler.

Architecture

Slim workload: wasm-tools-coreclr extends only microsoft-net-sdk-emscripten (Emscripten SDK + build targets). No Mono runtime pack or AOT cross-compiler.
Runtime pack: Resolved by SDK via standard KnownRuntimePack — no workload override needed (unlike Mono, which must keep runtime pack in lockstep with AOT compiler).
Opt-in: UseMonoRuntime=false in external projects; RuntimeFlavor=CoreCLR in-tree.
CoreCLR WASM uses interpreter, not JIT.

Changes

File	Description
`WorkloadManifest.json.in`	Added `wasm-tools-coreclr` workload definition
`WorkloadManifest.targets.in`	CoreCLR import group, guarded Mono imports
`Sdk.targets.in`	Conditional CoreCLR targets import when `UseMonoRuntime=false`
`BrowserWasmApp.CoreCLR.targets`	Guarded imports, inlined GenerateEmccExports, fixed BeforeTargets ordering for static web assets, added satellite assembly handling for nested publish
`eng/liveBuilds.targets`	Fixed `libminipal.a` exclusion from CoreCLR browser-wasm runtime pack
`PInvokeTableGeneratorTests.cs`	Fixed CoreCLR pinvoke table filename (`callhelpers-pinvoke.cpp`)
`WebAssembly.Sdk.pkgproj`	Added `BrowserWasmApp.CoreCLR.targets` to SDK package

CI Context

The existing CoreCLR_WasmBuildTests CI legs (added by #127073, #128296, #128762) already run DllImportTests, PInvokeTableGeneratorTests, NativeBuildTests, NativeLibraryTests, SatelliteAssembliesTests, IcuTests and more on CoreCLR — all currently passing on main without workloads (using in-tree build targets). The env vars (RUNTIME_FLAVOR_FOR_TESTS, CORECLR_VM_WASM_INCLUDE_DIR, MINIPAL_INCLUDE_DIR, etc.) are properly wired via Wasm.Build.Tests.csproj RunScriptCommands + RunScriptTemplate.sh.

This PR adds the workload packaging so that external consumers (outside the repo) can use the same native relinking pipeline. It also fixes several build pipeline bugs found during validation:

libminipal.a missing from runtime pack — only existed in sharedFramework/ subdir, was excluded by the glob in eng/liveBuilds.targets
Static web asset ordering — _ComputeWasmBuildCandidates ran before native relink completed, freezing stale candidates
Satellite assemblies in nested publish — _GatherWasmFilesToBuild overwrote WasmAssembliesToBundle during nested publish, dropping app satellite assemblies

Related Work

[wasm][wasi] CoreCLR wasi draft #130051 — WASI enabling PR with PInvokeTableGenerator and dlopen changes that are relevant to the WasmImportLinkage / native thunk generation pipeline shared between browser-wasm and WASI targets

Test Results (local validation, non-AOT)

Test Suite	CoreCLR	Notes
DllImportTests	12/12 ✅	Full parity with Mono
PInvokeTableGeneratorTests	23/24 ✅	1 debug-only assert (Release works)
BuildPublishTests	2/2 ✅	Full parity
NativeBuildTests	2/2 ✅	Template tests pass with proper env setup
NativeLibraryTests	4/4 ✅	SkiaSharp skipped (ActiveIssue#103566, pre-existing, fails Mono too)
SatelliteAssembliesTests	24/24 ✅	Full parity (after fix #3 above)

Known expected failures (not regressions)

AOT (12 tests) — out of scope, no AOT compiler for CoreCLR WASM
Mono ICall (2 tests) — HandleRef uses Mono-specific ICalls, N/A for CoreCLR
runtime#120897 (2 tests) — PORTABILITY_ASSERT: Indirect struct return (known limitation)
Debug assert (1 test) — precode_portable.cpp:35 with [UnmanagedCallersOnly] in namespaced types; Release works

Future Work

Enable category=workload tests on CoreCLR (currently excluded via -notrait filter in csproj line 109)
Blazor WebAssembly integration path with CoreCLR
_WasmNativeWorkloadNeeded detection (currently has Mono-specific triggers)

Note

This PR description was generated with assistance from GitHub Copilot.

Add a new 'wasm-tools-coreclr' workload that provides native relinking support for CoreCLR browser-wasm projects without pulling in Mono dependencies (MonoAOTCompiler, MonoTargets.Sdk, Mono runtime pack). Unlike Mono, CoreCLR doesn't need its runtime pack bundled in the workload — the SDK resolves it via the standard KnownRuntimePack mechanism. The workload only provides: - Build targets for native relinking (BrowserWasmApp.CoreCLR.targets) - Emscripten SDK (shared via microsoft-net-sdk-emscripten) Changes: - Package BrowserWasmApp.CoreCLR.targets into WebAssembly.Sdk NuGet pack - Add conditional import in Sdk.targets.in (UseMonoRuntime switches path) - Add wasm-tools-coreclr workload to manifest (no Mono deps) - Add CoreCLR import group in WorkloadManifest.targets.in - Skip MonoAOTCompiler import when UseMonoRuntime=false Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Guard the native.wasm.targets import with a condition so it only loads when RepositoryEngineeringDir is set (in-tree builds). For the workload path, inline the GenerateEmccExports target with the required exported runtime methods and functions. Emscripten SDK acquisition is already handled by EmSdkRepo.Defaults.props + the emscripten workload extension. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

- Include libminipal.a in browser-wasm CoreCLR runtime pack. It was excluded from LibrariesSharedFrameworkDir glob but unlike libz.a and libSystem.IO.Compression.Native.a it only exists in sharedFramework/ (not the parent LibrariesNativeArtifactsPath), so the exclusion prevented it from shipping at all. libminipal.a is a distinct library from libcoreclrminipal.a and is needed by the emcc linker. - Fix PInvokeTableGeneratorTests to use correct CoreCLR output filename callhelpers-pinvoke.cpp instead of pinvoke-table.cpp. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

The _CoreCLRWasmNativeForBuild target must run before _ComputeWasmBuildCandidates (not just _ResolveWasmOutputs) so the relinked dotnet.native.wasm replaces the runtime pack version in the static web assets pipeline. Without this, the runtime pack binary is served and user P/Invoke modules fail with DllNotFoundException. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

During nested publish, _GatherWasmFilesToPublish populates WasmAssembliesToBundle from ResolvedFileToPublish (which includes app satellite assemblies). The CoreCLR build pipeline was calling _GatherWasmFilesToBuild which overwrites this list with build-time items that omit app satellites, causing ComputeWasmPublishAssets to fail. Introduce _CoreCLRGatherWasmFiles wrapper that skips _GatherWasmFilesToBuild during nested publish, preserving the publish-time assembly list. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Copilot

Pull request overview

This PR prototypes enabling a “CoreCLR browser-wasm” path to use the existing WebAssembly workload/tooling pipeline (Emscripten + relinking + P/Invoke table generation) without pulling in Mono runtime/AOT components, primarily by routing imports/targets based on UseMonoRuntime=false.

Changes:

Added a new wasm-tools-coreclr workload and updated workload target imports to avoid Mono/AOT packs when UseMonoRuntime == false.
Updated the WebAssembly SDK target selection to import a CoreCLR-specific BrowserWasmApp.CoreCLR.targets when UseMonoRuntime == false.
Adjusted CoreCLR WASM build/publish orchestration and fixed a CoreCLR test expectation for the generated P/Invoke table filename.

Reviewed changes

Copilot reviewed 7 out of 7 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
src/mono/wasm/Wasm.Build.Tests/PInvokeTableGeneratorTests.cs	Updates CoreCLR expectation to `callhelpers-pinvoke.cpp` for the generated P/Invoke table file.
src/mono/nuget/Microsoft.NET.Workload.Mono.Toolchain.Current.Manifest/WorkloadManifest.targets.in	Guards Mono/AOT imports behind `UseMonoRuntime != false` and adds a CoreCLR browser-wasm import group for WebAssembly.Sdk only.
src/mono/nuget/Microsoft.NET.Workload.Mono.Toolchain.Current.Manifest/WorkloadManifest.json.in	Adds the `wasm-tools-coreclr` workload definition (slimmed to SDK/emscripten packs).
src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/Sdk/Sdk.targets.in	Selects Mono vs CoreCLR browser targets based on `UseMonoRuntime`.
src/mono/nuget/Microsoft.NET.Runtime.WebAssembly.Sdk/Microsoft.NET.Runtime.WebAssembly.Sdk.pkgproj	Ensures `BrowserWasmApp.CoreCLR.targets` is packed into the SDK.
src/mono/browser/build/BrowserWasmApp.CoreCLR.targets	Adds in-tree import guards, inlines emcc exports for workload scenarios, fixes target ordering for build/static web assets, and avoids overwriting publish-time assembly lists during nested publish.
eng/liveBuilds.targets	Stops excluding `libminipal.a` from the CoreCLR browser-wasm runtime pack live-build file set.

lewing · 2026-07-05T23:56:16Z

We don't really need anything but emsdk for coreclr but I went ahead and matched the wasmsdk logic to avoid getting different versions for the same workload for now.

Remove the PORTABILITY_ASSERT for indirect struct returns in the CoreCLR WASM interp-to-native thunk generator. For struct return types (S<N> tokens), emit C typedefs of the correct size so emcc generates the proper sret ABI calling convention. This fixes the runtime crash when CoreCLR WASM code calls native functions that return structs. Also remove the native-mono test category filter from EnsureWasmAbiRulesAreFollowedInInterpreter since it now works on CoreCLR. Fixes dotnet#120897 Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Restore the exclusion of libminipal.a from the LibrariesSharedFrameworkDir glob. The file is already included via CoreCLRSharedFrameworkDir (line 111), so including it from both locations causes NU5118 duplicate file error during nupkg creation. Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

akoeplinger · 2026-07-06T08:06:31Z

+      "packs": [
+        "Microsoft.NET.Runtime.WebAssembly.Sdk.${NetVersion}",
+        "Microsoft.NET.Sdk.WebAssembly.Pack.${NetVersion}"
+      ],


should probably add the coreclr browser-wasm runtime pack here
(and as you know this will need to actually be done in the sdk repo as well)

pavelsavara · 2026-07-06T10:20:31Z

             TaskFactory="TaskHostFactory"
             Condition="'$(WasmAppBuilderTasksAssemblyPath)' != ''" />

+  <!-- Exported runtime methods and functions for the emcc link step.


In Mono we store some of the build/link flags as json file and restore it into MSBuild properties. I don't remember what was our original motivation for that. Maybe DRY ?

lewing and others added 5 commits July 5, 2026 12:18

Copilot AI review requested due to automatic review settings July 5, 2026 23:22

github-actions Bot added the area-Build-mono label Jul 5, 2026

Copilot started reviewing on behalf of lewing July 5, 2026 23:22 View session

Copilot AI reviewed Jul 5, 2026

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lewing requested a review from pavelsavara July 5, 2026 23:41

lewing added this to the 11.0.0 milestone Jul 5, 2026

lewing and others added 2 commits July 5, 2026 18:57

akoeplinger reviewed Jul 6, 2026

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pavelsavara reviewed Jul 6, 2026

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[WIP] Enable wasm-tools workload for CoreCLR WASM targets#130226

[WIP] Enable wasm-tools workload for CoreCLR WASM targets#130226
lewing wants to merge 7 commits into
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Summary

Architecture

Changes

CI Context

Related Work

Test Results (local validation, non-AOT)

Known expected failures (not regressions)

Future Work

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lewing commented Jul 5, 2026

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lewing commented Jul 5, 2026 •

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