fix: don't fail or crash when the USB bus is missing

src/lib.rs

@@ -163,25 +163,24 @@ impl Drop for Emitter {
     }
 }
 
-async fn list_devices(error_prefix: &'static str) -> Result<Vec<nusb::DeviceInfo>> {
+async fn list_devices() -> Result<Vec<nusb::DeviceInfo>> {
     run_blocking(move || {
-        nusb::list_devices()
+        Ok(nusb::list_devices()
             .wait()
-            .map(|devices| devices.collect::<Vec<_>>())
-            .map_err(|e| format!("{error_prefix} error: {e}"))
+            .map_or(Vec::new(), |devices| devices.collect::<Vec<_>>()))
     })
     .await
 }
 
 #[napi(js_name = "nativeGetDevices")]
 pub async fn getDevices() -> Result<Vec<UsbDevice>> {
-    let devices = list_devices("getDevices").await?;
+    let devices = list_devices().await?;
     Ok(devices.into_iter().map(UsbDevice::new).collect())
 }
 
 #[napi(js_name = "nativeFindDeviceByIds")]
 pub async fn findDeviceByIds(vendorId: u16, productId: u16) -> Result<Option<UsbDevice>> {
-    let device = list_devices("findDeviceByIds")
+    let device = list_devices()
         .await?
         .into_iter()
         .find(|dev| dev.vendor_id() == vendorId && dev.product_id() == productId);
@@ -190,7 +189,7 @@ pub async fn findDeviceByIds(vendorId: u16, productId: u16) -> Result<Option<Usb
 
 #[napi(js_name = "nativeFindDeviceBySerial")]
 pub async fn findDeviceBySerial(serialNumber: String) -> Result<Option<UsbDevice>> {
-    let device = list_devices("findDeviceBySerial")
+    let device = list_devices()
         .await?
         .into_iter()
         .find(|dev| dev.serial_number() == Some(serialNumber.as_str()));

test/webusb.js

@@ -29,6 +29,33 @@ describe('WebUSB Module', () => {
     it('should describe basic constants', () => {
         assert.notEqual(webusb, undefined, 'webusb must be undefined');
     });
+
+    it('should not throw when the hotplug watcher cannot start', async () => {
+        const customWebusb = new WebUSB();
+        const listener = () => {};
+        const expectedError = new Error('watch devices error');
+        const warnings = [];
+        const originalWarn = console.warn;
+
+        customWebusb.nativeEmitter = {
+            addAttach: async () => { throw expectedError; },
+            addDetach: async () => {},
+            removeAttach: async () => {},
+            removeDetach: async () => {},
+        };
+
+        console.warn = (...args) => warnings.push(args);
+
+        try {
+            customWebusb.addEventListener('connect', listener);
+            await new Promise(resolve => setImmediate(resolve));
+
+            assert.ok(warnings.some(args => args[0] === 'usb: hotplug watcher error:' && args[1] === expectedError));
+        } finally {
+            customWebusb.removeEventListener('connect', listener);
+            console.warn = originalWarn;
+        }
+    });
 });
 
 describe('allowedDevices', () => {

tsc/index.ts

@@ -148,7 +148,9 @@ class WebUSB extends EventTarget implements USB {
     private queueNativeEmitterOperation(operation: () => Promise<void>): void {
         const pending = this.nativeEmitterQueue.then(operation);
         this.nativeEmitterQueue = pending.catch(() => {});
-        pending.catch(error => setTimeout(() => { throw error; }, 0));
+        // A hotplug watcher that can't start (e.g. no netlink in a container) must
+        // not crash the host process, so report it rather than rethrowing.
+        pending.catch(error => console.warn('usb: hotplug watcher error:', error));
     }
 
     private deviceConnectCallback = async (device: UsbDevice) => {
@@ -194,7 +196,9 @@ class WebUSB extends EventTarget implements USB {
                 await this.nativeEmitter.addAttach(this.deviceConnectCallback);
                 await this.nativeEmitter.addDetach(this.deviceDisconnectCallback);
             });
-            nativeGetDevices().then(devices => devices.forEach(device => this.knownDevices.set(device.handle, device)));
+            nativeGetDevices()
+                .then(devices => devices.forEach(device => this.knownDevices.set(device.handle, device)))
+                .catch(error => console.warn('usb: failed to list devices for hotplug:', error));
         }
     }