fix: address PR review comments

- Fix napi_create_string_utf8 length parameter cast (isize  usize)
- Fix formatted error string using concat!() to avoid embedded whitespace

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>
Signed-off-by: Simon Davies <simongdavies@users.noreply.github.com>

Author: simongdavies

src/hyperlight-js-runtime/src/lib.rs

@@ -26,8 +26,8 @@ pub(crate) mod utils;
 use alloc::format;
 use alloc::rc::Rc;
 use alloc::string::{String, ToString};
-use core::cell::RefCell;
 use alloc::vec::Vec;
+use core::cell::RefCell;
 
 use anyhow::{anyhow, Context as _};
 use hashbrown::HashMap;

src/hyperlight-js/src/lib.rs

@@ -27,13 +27,13 @@ mod script;
 pub mod sandbox;
 
 use hyperlight_host::func::HostFunction;
+// Re-export FnReturn for the NAPI bridge (used in register_js signature).
+#[doc(hidden)]
+pub use sandbox::host_fn::FnReturn;
 /// Validate a module identifier (name or namespace).
 pub use sandbox::js_sandbox::validate_module_identifier;
 /// Validate that a namespace is not reserved.
 pub use sandbox::js_sandbox::validate_namespace_not_reserved;
-// Re-export FnReturn for the NAPI bridge (used in register_js signature).
-#[doc(hidden)]
-pub use sandbox::host_fn::FnReturn;
 /// A Hyperlight Sandbox with a JavaScript run time loaded but no guest code.
 pub use sandbox::js_sandbox::JSSandbox;
 /// Default namespace for user modules added via [`JSSandbox::add_module`].

src/hyperlight-js/src/sandbox/host_fn.rs

@@ -202,9 +202,11 @@ impl HostModule {
                 // data is not supported — reject if blobs are present.
                 if !blobs.is_empty() {
                     return Err(crate::HyperlightError::Error(format!(
-                        "Function '{}' received {} binary argument(s) but was registered \
-                        with `register` (typed JSON-only). Use `register_js` for functions \
-                        that accept Uint8Array/Buffer arguments.",
+                        concat!(
+                            "Function '{}' received {} binary argument(s) but was registered ",
+                            "with `register` (typed JSON-only). Use `register_js` for functions ",
+                            "that accept Uint8Array/Buffer arguments.",
+                        ),
                         name,
                         blobs.len()
                     )));

src/hyperlight-js/tests/user_modules.rs

@@ -507,7 +507,7 @@ fn user_module_can_import_builtin_module() {
 fn user_module_can_import_host_function() {
     let enricher_module = Script::from_content(
         r#"
-        import * as db from 'host:db';
+        import * as db from 'db';
         export function enrich(event) {
             const user = db.lookup(event.userId);
             event.userName = user.name;
@@ -526,15 +526,13 @@ fn user_module_can_import_host_function() {
     );
 
     let mut proto = SandboxBuilder::new().build().unwrap();
-    proto.host_module("host:db").register_raw(
-        "lookup",
-        |args: String| -> hyperlight_js::Result<String> {
-            let parsed: serde_json::Value = serde_json::from_str(&args).unwrap();
-            let id = parsed[0].as_i64().unwrap();
-            let result = serde_json::json!({ "id": id, "name": format!("User {}", id) });
-            Ok(serde_json::to_string(&result).unwrap())
-        },
-    );
+    proto
+        .register(
+            "db",
+            "lookup",
+            |id: i32| serde_json::json!({ "id": id, "name": format!("User {}", id) }),
+        )
+        .unwrap();
 
     let mut sandbox = proto.load_runtime().unwrap();