From 897babc2f5afd6502e14887edc69979834ec824a Mon Sep 17 00:00:00 2001
From: Artyom Sovetnikov <2056864+Elringus@users.noreply.github.com>
Date: Mon, 11 May 2026 20:27:33 +0300
Subject: [PATCH] allow empty modules

---
 .../Runtime/InteropServices/JavaScript/JSImportTest.cs      | 6 ++++++
 .../InteropServices/JavaScript/JavaScriptTestHelper.cs      | 3 +++
 .../InteropServices/JavaScript/JavaScriptTestHelper.mjs     | 5 +++++
 src/mono/browser/runtime/invoke-js.ts                       | 2 +-
 4 files changed, 15 insertions(+), 1 deletion(-)

diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportTest.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportTest.cs
index ee9271e52c2859..d5579849ca201f 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportTest.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JSImportTest.cs
@@ -58,6 +58,12 @@ public async Task MissingImportAsync()
             Assert.Contains("intentionallyMissingImportAsync must be a Function but was undefined", ex.Message);
         }
 
+        [Fact]
+        public void EmptyModuleNameImport()
+        {
+            Assert.Equal("empty module", JavaScriptTestHelper.EmptyModuleNameEcho("empty module"));
+        }
+
 #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()
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.cs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.cs
index d1fffe5517452d..b80e0c43d4b02e 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.cs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.cs
@@ -46,6 +46,9 @@ public static void ConsoleWriteLine([JSMarshalAs<JSType.String>] string message)
         [JSImport("intentionallyMissingImportAsync", "JavaScriptTestHelper")]
         public static partial Task IntentionallyMissingImportAsync();
 
+        [JSImport("emptyModuleNameEcho", "")]
+        public static partial string EmptyModuleNameEcho(string message);
+
         [JSImport("catch1toString", "JavaScriptTestHelper")]
         public static partial string catch1toString(string message, string functionName);
 
diff --git a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.mjs b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.mjs
index 1c91dbdb1dfe6b..ad63b7ee3a7250 100644
--- a/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.mjs
+++ b/src/libraries/System.Runtime.InteropServices.JavaScript/tests/System.Runtime.InteropServices.JavaScript.UnitTests/System/Runtime/InteropServices/JavaScript/JavaScriptTestHelper.mjs
@@ -495,6 +495,11 @@ globalThis.rebound = {
 
 export async function setup() {
     dllExports = await App.runtime.getAssemblyExports("System.Runtime.InteropServices.JavaScript.Tests.dll");
+    App.runtime.setModuleImports("", { emptyModuleNameEcho });
+}
+
+function emptyModuleNameEcho(message) {
+    return message;
 }
 
 // console.log('JavaScriptTestHelper:' Object.keys(globalThis.JavaScriptTestHelper));
diff --git a/src/mono/browser/runtime/invoke-js.ts b/src/mono/browser/runtime/invoke-js.ts
index 63e6731f46b909..f1a0710fce568e 100644
--- a/src/mono/browser/runtime/invoke-js.ts
+++ b/src/mono/browser/runtime/invoke-js.ts
@@ -382,7 +382,7 @@ function mono_wasm_lookup_js_import (function_name: string, js_module_name: stri
 
     let scope: any = {};
     const parts = function_name.split(".");
-    if (js_module_name) {
+    if (js_module_name != null) {
         scope = importedModules.get(js_module_name);
         if (WasmEnableThreads) {
             mono_assert(scope, () => `ES6 module ${js_module_name} was not imported yet, please call JSHost.ImportAsync() on the UI or JSWebWorker thread first in order to invoke ${function_name}.`);