test for failed bind of JSImport

make it exception instead of abort

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

@@ -36,6 +36,13 @@ public async Task MultipleImportAsync()
             instance1.Dispose();
         }
 
+        [Fact]
+        public void MissingImport()
+        {
+            var ex = Assert.Throws<JSException>(() => JavaScriptTestHelper.IntentionallyMissingImport());
+            Assert.Contains("intentionallyMissingImport 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

@@ -37,6 +37,9 @@ public static void ConsoleWriteLine([JSMarshalAs<JSType.String>] string message)
         [JSImport("delay", "JavaScriptTestHelper")]
         public static partial Task Delay(int ms);
 
+        [JSImport("intentionallyMissingImport", "JavaScriptTestHelper")]
+        public static partial void IntentionallyMissingImport();
+
         [JSImport("catch1toString", "JavaScriptTestHelper")]
         public static partial string catch1toString(string message, string functionName);
 

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

@@ -42,7 +42,13 @@ export function mono_wasm_invoke_jsimport_MT(signature: JSFunctionSignature, arg
     let bound_fn = js_import_wrapper_by_fn_handle[function_handle];
     if (bound_fn == undefined) {
         // it was not bound yet, let's do it now
-        bound_fn = bind_js_import(signature);
+        try {
+            bound_fn = bind_js_import(signature);
+        } catch (ex: any) {
+            Module.err(ex.toString());
+            marshal_exception_to_cs(<any>args, ex);
+            return;
+        }
     }
     mono_assert(bound_fn, () => `Imported function handle expected ${function_handle}`);
 
@@ -389,14 +395,18 @@ function mono_wasm_lookup_js_import(function_name: string, js_module_name: strin
     for (let i = 0; i < parts.length - 1; i++) {
         const part = parts[i];
         const newscope = scope[part];
-        mono_assert(newscope, () => `${part} not found while looking up ${function_name}`);
+        if (!newscope) {
+            throw new Error(`${part} not found while looking up ${function_name}`);
+        }
         scope = newscope;
     }
 
     const fname = parts[parts.length - 1];
     const fn = scope[fname];
 
-    mono_assert(typeof (fn) === "function", () => `${function_name} must be a Function but was ${typeof fn}`);
+    if (typeof (fn) !== "function") {
+        throw new Error(`${function_name} must be a Function but was ${typeof fn}`);
+    }
 
     // if the function was already bound to some object it would stay bound to original object. That's good.
     return fn.bind(scope);