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Pull request overview
This PR refactors Browser/WASM scheduling and JS interop entrypoints, moving away from legacy mono internal-call/reflection-based paths toward LibraryImport/UnmanagedCallersOnly-style exports, and introduces new scheduling hooks for finalization and diagnostic server work.
Changes:
- Update Browser/WASM scheduling to use idempotent scheduling (
SystemJS_Schedule*) and a unifiedrunBackgroundTimers()runner. - Restructure JS interop exports/binding to use handle-based JSExport invocation (
SystemInteropJS_CallJSExport) and add new native entrypoints (e.g.,BrowserHost_ExecuteAssembly). - Adjust build/pinvoke module lists and remove older mono-only glue code and declarations.
Reviewed changes
Copilot reviewed 38 out of 38 changed files in this pull request and generated 4 comments.
Show a summary per file
| File | Description |
|---|---|
| src/native/libs/System.Native.Browser/native/scheduling.ts | Makes background/finalization scheduling idempotent (no reschedule/cancel). |
| src/mono/wasm/build/WasmApp.Common.targets | Adds browser-only native modules to the pinvoke module list. |
| src/mono/mono/utils/mono-threads.h | Removes DISABLE_THREADS declarations for background/ds job scheduling. |
| src/mono/mono/utils/mono-threads-wasm.h | Removes DISABLE_THREADS declarations for background/ds exec entrypoints. |
| src/mono/mono/utils/mono-threads-wasm.c | Removes legacy DISABLE_THREADS background/ds job queue/executors. |
| src/mono/mono/sgen/sgen-client.h | Removes sgen_client_schedule_background_job API declaration. |
| src/mono/mono/mini/mini-wasm.h | Removes DISABLE_THREADS JS-import declarations for timers/background jobs. |
| src/mono/mono/mini/mini-wasm.c | Removes legacy DISABLE_THREADS timer/background job wiring and internal calls. |
| src/mono/mono/metadata/sgen-mono.c | Removes HOST_WASM/DISABLE_THREADS background job scheduling shim. |
| src/mono/mono/metadata/gc.c | Switches DISABLE_THREADS wasm finalization notification to SystemJS_ScheduleFinalization. |
| src/mono/mono/eventpipe/ep-rt-mono.h | Adds browser-only ds job scheduling/execute callback declarations for single-threaded queueing. |
| src/mono/mono/eventpipe/ep-rt-mono.c | Implements browser-only ds job scheduling queue and execute callback. |
| src/mono/browser/runtime/types/internal.ts | Adds JSExportHandle and replaces background/ds helpers with runBackgroundTimers. |
| src/mono/browser/runtime/scheduling.ts | Reworks scheduling: unified runBackgroundTimers + new SystemJS_Schedule* APIs. |
| src/mono/browser/runtime/runtime.h | Removes mono_wasm_assembly_find_method export declaration. |
| src/mono/browser/runtime/runtime.c | Removes mono_wasm_assembly_find_method; hardens token-based lookup with null check. |
| src/mono/browser/runtime/run.ts | Changes main execution to call native BrowserHost_ExecuteAssembly and resolve/reject a JS promise via new callbacks. |
| src/mono/browser/runtime/marshal-to-js.ts | Updates comments to remove call_entry_point reference. |
| src/mono/browser/runtime/managed-exports.ts | Removes legacy managed-exports method lookup/async invoke paths; introduces UCO/handle invoke helpers. |
| src/mono/browser/runtime/loader/exit.ts | Formatting + avoids attempting node stream flush outside Node. |
| src/mono/browser/runtime/invoke-cs.ts | Switches bindings to invoke JSExports via JSExportHandle + handle-based call helper. |
| src/mono/browser/runtime/exports.ts | Exposes runBackgroundTimers instead of legacy background/ds exec helpers. |
| src/mono/browser/runtime/exports-binding.ts | Updates the wasm import list to new scheduling + main-promise resolution hooks. |
| src/mono/browser/runtime/driver.c | Removes legacy invoke_jsexport plumbing; adds BrowserHost_ExecuteAssembly. |
| src/mono/browser/runtime/diagnostics/common.ts | Uses runBackgroundTimers during diagnostic server event loop. |
| src/mono/browser/runtime/cwraps.ts | Updates cwrap signatures to new entrypoints and removes old ones. |
| src/mono/browser/runtime/corebindings.c | Removes legacy internal-call registration and export lookup/bind helpers. |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.cs | Removes legacy managed entrypoint invocation (CallEntrypoint). |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.Mono.cs | Deletes mono-specific BindManagedFunction/BindAssemblyExports implementation. |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/JSHostImplementation.CoreCLR.cs | Improves exception typing + unwraps TargetInvocationException preserving stack. |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptExports.cs | Adds/extends UnmanagedCallersOnly exports and managed-threads handling in exports. |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptExports.Mono.cs | Adds EntryPoint names for select exports; trims legacy entrypoint/bind exports code. |
| src/libraries/System.Runtime.InteropServices.JavaScript/src/System.Runtime.InteropServices.JavaScript.csproj | Switches to unified Interop.Runtime + adjusts included interop/export files. |
| src/libraries/System.Private.CoreLib/src/System/Threading/TimerQueue.Browser.cs | Switches to LibraryImport-based SystemJS_ScheduleTimer for MONO/browser. |
| src/libraries/System.Private.CoreLib/src/System/Threading/ThreadPool.Browser.cs | Switches to LibraryImport-based SystemJS_ScheduleBackgroundJob for MONO/browser. |
| src/libraries/System.Private.CoreLib/src/System/Runtime/CompilerServices/AsyncHelpers.Browser.cs | Adds MONO/browser LibraryImport for main-promise resolve/reject hooks. |
| src/libraries/Common/src/Interop/Browser/Interop.Runtime.cs | Removes unused browser interop entrypoint APIs (BindAssemblyExports/GetAssemblyExport/AssemblyGetEntryPoint). |
| src/libraries/Common/src/Interop/Browser/Interop.Runtime.Mono.cs | Deletes mono-specific internal-call declarations for runtime interop. |
Comments suppressed due to low confidence (2)
src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptExports.cs:55
- In the FEATURE_WASM_MANAGED_THREADS branch, this uses
arg_excbut the variable declared in this method isargException. As written this won’t compile; update the reference to use the correct variable when callingAssertCurrentThreadContext().
src/libraries/System.Runtime.InteropServices.JavaScript/src/System/Runtime/InteropServices/JavaScript/Interop/JavaScriptExports.cs:139 ctx.ReleasePromiseHolder(arg_1.slot.GCHandle)referencesarg_1, but this method definesarg1(and notarg_1). This is a compile-time error; use the correct argument variable when releasing the holder.
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
Co-authored-by: Copilot <175728472+Copilot@users.noreply.github.com>
This was referenced Feb 25, 2026
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Unify Mono and CoreCLR JS interop code paths for single-threaded Browser WASM
This PR eliminates the separate Mono-specific code paths in the Browser WASM JS interop layer, aligning Mono with the pattern already used by CoreCLR. This is a step toward running CoreCLR on WASM with a shared managed/JS codebase.
Key changes
Replace Mono internal calls with
[LibraryImport]P/InvokesTimerQueue.Browser.cs) and thread pool (ThreadPool.Browser.cs) now use[LibraryImport]for both Mono and CoreCLR instead of Mono-only[MethodImpl(MethodImplOptions.InternalCall)].AsyncHelpers.Browser.csconditionally targetslibSystem.Native.Browser(Mono) or QCall (CoreCLR).Replace
mono_wasm_invoke_jsexportwith[UnmanagedCallersOnly]entry pointsCallDelegate,CompleteTask,ReleaseJSOwnedObjectByGCHandle,GetManagedStackTrace,LoadLazyAssembly,LoadSatelliteAssembly,InstallMainSynchronizationContext,BindAssemblyExports) are now called directly as C-exported functions via[UnmanagedCallersOnly(EntryPoint = "...")]rather than looked up by name and dispatched throughmono_runtime_invoke.cwrapsinstead of via theManagedExportsobject +mono_wasm_invoke_jsexport.JavaScriptExports.CoreCLR.csis renamed toJavaScriptExports.cs(shared) and gains the thread-blocking-mode logic previously only inJavaScriptExports.Mono.cs.New
BrowserHost_ExecuteAssemblyfor entry point executionCallEntrypointmanaged export →AssemblyGetEntryPointicall) with a direct C functionBrowserHost_ExecuteAssemblythat callsmono_runtime_run_main.SystemJS_ResolveMainPromise/SystemJS_RejectMainPromiseexported from managed code.Separate scheduling concerns
SystemJS_ScheduleBackgroundJob(cb)/mono_background_execwhich multiplexed timer, thread pool, finalization, and diagnostics callbacks is split into four dedicated pairs:SystemJS_ScheduleTimer/SystemJS_ExecuteTimerCallbackSystemJS_ScheduleBackgroundJob/SystemJS_ExecuteBackgroundJobCallbackSystemJS_ScheduleFinalization/SystemJS_ExecuteFinalizationCallbackSystemJS_ScheduleDiagnosticServerJob/SystemJS_ExecuteDiagnosticServerCallbackP/Invoke module registration for Mono
WasmApp.Common.targetsaddslibSystem.Native.BrowserandlibSystem.Runtime.InteropServices.JavaScript.Nativeto_WasmPInvokeModulesfor browser projects.Deleted code
Interop.Runtime.Mono.cs— Mono-specific internal call declarationsJSHostImplementation.Mono.cs— Mono-specificBindAssemblyExports/BindManagedFunctionvia icallscorebindings.c—bindings_initialize_internals,SystemInteropJS_AssemblyGetEntryPoint,SystemInteropJS_BindAssemblyExports,SystemInteropJS_GetAssemblyExportdriver.c—mono_wasm_invoke_jsexport, async/sync JSExport dispatchmono-threads-wasm.c—SystemJS_ScheduleBackgroundJob(cb),mono_background_exec,mono_wasm_ds_execmini-wasm.c—SystemJS_ScheduleTimer,mono_wasm_execute_timer, internal call registrationssgen-mono.c—sgen_client_schedule_background_jobOther improvements
mono_wasm_get_method_matchingnow null-checks the result ofmono_get_methodbefore dereferencing.JSHostImplementation.CoreCLR.csunwrapsTargetInvocationExceptionusingExceptionDispatchInfoto preserve original stack traces.ArithmeticExceptiontoArgumentExceptionfor assembly binding errors.Scope
Single-threaded browser only (
DISABLE_THREADS). Multi-threaded paths haveTODO-WASM: unificationmarkers.