fix: bare specifier handling

Author: NathanWalker

NativeScript/runtime/ModuleInternalCallbacks.mm

@@ -1291,16 +1291,9 @@ static bool IsDocumentsPath(const std::string& path) {
         absPath = builtinPath;
       }
     } else if (IsLikelyOptionalModule(spec)) {
-      // In debug/test builds, surface a clear unresolved bare specifier error instead of
-      // synthesizing a placeholder module; more helpful signal during development.
-      if (RuntimeConfig.IsDebug) {
-        std::string msg = "Cannot resolve bare specifier '" + spec + "'";
-        isolate->ThrowException(v8::Exception::Error(tns::ToV8String(isolate, msg.c_str())));
-        return v8::MaybeLocal<v8::Module>();
-      }
-
-      // In release builds, create a placeholder that throws on use,
-      // so apps can guard optional imports without crashing at import time.
+      // Treat bare specifiers as optional modules by creating a placeholder ES module that
+      // throws on property access. This lets applications guard optional imports at runtime
+      // without crashing during startup, especially in development.
       std::string appPath = RuntimeConfig.ApplicationPath;
       std::string placeholderPath = NormalizePath(appPath + "/" + spec + ".mjs");
 
@@ -1330,10 +1323,16 @@ static bool IsDocumentsPath(const std::string& path) {
           // File created successfully, now resolve it normally
           absPath = placeholderPath;
         } else {
-          // Failed to create file, fall back to throwing error
+          // Failed to create file. In debug, avoid throwing to keep dev sessions alive; in release
+          // throw to surface the missing optional module.
           std::string msg = "Cannot find module " + spec + " (tried " + absPath + ")";
-          isolate->ThrowException(v8::Exception::Error(tns::ToV8String(isolate, msg)));
-          return v8::MaybeLocal<v8::Module>();
+          if (RuntimeConfig.IsDebug) {
+            Log(@"Debug mode - Optional module placeholder creation failed: %s", msg.c_str());
+            return v8::MaybeLocal<v8::Module>();
+          } else {
+            isolate->ThrowException(v8::Exception::Error(tns::ToV8String(isolate, msg)));
+            return v8::MaybeLocal<v8::Module>();
+          }
         }
       } else {
         // Placeholder file already exists, use it

TestRunner/app/tests/HttpEsmLoaderTests.js

@@ -16,12 +16,24 @@ describe("HTTP ESM Loader", function() {
             });
         });
         it("should surface helpful errors for unresolved bare specifiers", function(done) {
-            import("bare-spec-example").then(function() {
-                (done.fail ? done.fail : fail)("Bare specifier should not have resolved successfully");
+            import("bare-spec-example").then(function(mod) {
+                // Placeholder modules export a default Proxy. Accessing a property on that proxy
+                // should throw with a helpful error message containing the specifier.
+                let threw = false;
+                try {
+                    // Trigger the proxy's get trap by accessing a property on the default export
+                    // eslint-disable-next-line no-unused-expressions
+                    mod && mod.default && mod.default.__touch__;
+                } catch (useErr) {
+                    threw = true;
+                    const msg = (useErr && useErr.message) ? useErr.message : String(useErr);
+                    expect(msg).toContain("bare-spec-example");
+                }
+                expect(threw).toBe(true);
                 done();
             }).catch(function(error) {
+                // Other runtimes throw on import; assert message includes the specifier name.
                 const message = (error && error.message) ? error.message : String(error);
-                // Expect our thrown helpful message containing the specifier name
                 expect(message).toContain("bare-spec-example");
                 done();
             });