[browser][MT] fix error propagation when calling JSImport of missing JS function

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

@@ -43,6 +43,13 @@ public void MissingImport()
             Assert.Contains("intentionallyMissingImport must be a Function but was undefined", ex.Message);
         }
 
+        [Fact]
+        public async Task MissingImportAsync()
+        {
+            var ex = await Assert.ThrowsAsync<JSException>(() => JavaScriptTestHelper.IntentionallyMissingImportAsync());
+            Assert.Contains("intentionallyMissingImportAsync must be a Function but was undefined", ex.Message);
+        }
+
 #if !FEATURE_WASM_MANAGED_THREADS // because in MT JSHost.ImportAsync is really async, it will finish before the caller could cancel it
         [Fact]
         public async Task CancelableImportAsync()

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

@@ -40,6 +40,9 @@ public static void ConsoleWriteLine([JSMarshalAs<JSType.String>] string message)
         [JSImport("intentionallyMissingImport", "JavaScriptTestHelper")]
         public static partial void IntentionallyMissingImport();
 
+        [JSImport("intentionallyMissingImportAsync", "JavaScriptTestHelper")]
+        public static partial Task IntentionallyMissingImportAsync();
+
         [JSImport("catch1toString", "JavaScriptTestHelper")]
         public static partial string catch1toString(string message, string functionName);
 

src/mono/browser/runtime/invoke-js.ts

@@ -4,8 +4,8 @@
 import WasmEnableThreads from "consts:wasmEnableThreads";
 import BuildConfiguration from "consts:configuration";
 
-import { marshal_exception_to_cs, bind_arg_marshal_to_cs } from "./marshal-to-cs";
-import { get_signature_argument_count, bound_js_function_symbol, get_sig, get_signature_version, get_signature_type, imported_js_function_symbol, get_signature_handle, get_signature_function_name, get_signature_module_name, is_receiver_should_free, get_caller_native_tid, get_sync_done_semaphore_ptr } from "./marshal";
+import { marshal_exception_to_cs, bind_arg_marshal_to_cs, marshal_task_to_cs } from "./marshal-to-cs";
+import { get_signature_argument_count, bound_js_function_symbol, get_sig, get_signature_version, get_signature_type, imported_js_function_symbol, get_signature_handle, get_signature_function_name, get_signature_module_name, is_receiver_should_free, get_caller_native_tid, get_sync_done_semaphore_ptr, get_arg } from "./marshal";
 import { forceThreadMemoryViewRefresh } from "./memory";
 import { JSFunctionSignature, JSMarshalerArguments, BoundMarshalerToJs, JSFnHandle, BoundMarshalerToCs, JSHandle, MarshalerType, VoidPtrNull } from "./types/internal";
 import { VoidPtr } from "./types/emscripten";
@@ -28,7 +28,6 @@ export function mono_wasm_bind_js_import_ST (signature: JSFunctionSignature): Vo
         bind_js_import(signature);
         return VoidPtrNull;
     } catch (ex: any) {
-        Module.err(ex.toString());
         return stringToUTF16Ptr(normalize_exception(ex));
     }
 }
@@ -45,9 +44,25 @@ export function mono_wasm_invoke_jsimport_MT (signature: JSFunctionSignature, ar
         try {
             bound_fn = bind_js_import(signature);
         } catch (ex: any) {
-            Module.err(ex.toString());
-            marshal_exception_to_cs(<any>args, ex);
-            return;
+            // propagate the exception back to caller, which could be on different thread. Handle both sync and async signatures.
+            try {
+                const res_sig = get_sig(signature, 1);
+                const res_type = get_signature_type(res_sig);
+                if (res_type === MarshalerType.Task) {
+                    const res = get_arg(args, 1);
+                    marshal_task_to_cs(res, Promise.reject(ex));
+                } else {
+                    marshal_exception_to_cs(<any>args, ex);
+                    if (monoThreadInfo.isUI) {
+                        const done_semaphore = get_sync_done_semaphore_ptr(args);
+                        tcwraps.mono_threads_wasm_sync_run_in_target_thread_done(done_semaphore);
+                    }
+                }
+                return;
+            } catch (ex2: any) {
+                runtimeHelpers.nativeExit(ex2);
+                return;
+            }
         }
     }
     mono_assert(bound_fn, () => `Imported function handle expected ${function_handle}`);

src/mono/browser/runtime/marshal-to-cs.ts

@@ -48,9 +48,9 @@ export function initialize_marshalers_to_cs (): void {
         js_to_cs_marshalers.set(MarshalerType.JSException, marshal_exception_to_cs);
         js_to_cs_marshalers.set(MarshalerType.JSObject, marshal_js_object_to_cs);
         js_to_cs_marshalers.set(MarshalerType.Object, marshal_cs_object_to_cs);
-        js_to_cs_marshalers.set(MarshalerType.Task, _marshal_task_to_cs);
-        js_to_cs_marshalers.set(MarshalerType.TaskResolved, _marshal_task_to_cs);
-        js_to_cs_marshalers.set(MarshalerType.TaskRejected, _marshal_task_to_cs);
+        js_to_cs_marshalers.set(MarshalerType.Task, marshal_task_to_cs);
+        js_to_cs_marshalers.set(MarshalerType.TaskResolved, marshal_task_to_cs);
+        js_to_cs_marshalers.set(MarshalerType.TaskRejected, marshal_task_to_cs);
         js_to_cs_marshalers.set(MarshalerType.Action, _marshal_function_to_cs);
         js_to_cs_marshalers.set(MarshalerType.Function, _marshal_function_to_cs);
         js_to_cs_marshalers.set(MarshalerType.None, _marshal_null_to_cs);// also void
@@ -295,7 +295,7 @@ function _marshal_function_to_cs (arg: JSMarshalerArgument, value: Function, _?:
 }
 
 
-function _marshal_task_to_cs (arg: JSMarshalerArgument, value: Promise<any>, _?: MarshalerType, res_converter?: MarshalerToCs) {
+export function marshal_task_to_cs (arg: JSMarshalerArgument, value: Promise<any>, _?: MarshalerType, res_converter?: MarshalerToCs) {
     const handleIsPreallocated = get_arg_type(arg) == MarshalerType.TaskPreCreated;
     if (value === null || value === undefined) {
         if (WasmEnableThreads && handleIsPreallocated) {
@@ -415,7 +415,7 @@ export function marshal_cs_object_to_cs (arg: JSMarshalerArgument, value: any):
             ) {
                 throw new Error("NotImplementedException: TypedArray");
             } else if (isThenable(value)) {
-                _marshal_task_to_cs(arg, value);
+                marshal_task_to_cs(arg, value);
             } else if (value instanceof Span) {
                 throw new Error("NotImplementedException: Span");
             } else if (js_type == "object") {