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

src/lib.rs

@@ -163,12 +163,20 @@ impl Drop for Emitter {
     }
 }
 
+// A Linux machine without a USB bus (often a container) has no
+// /sys/bus/usb/devices. That means there are no devices, not that listing failed.
+fn is_missing_usb_bus(e: &nusb::Error) -> bool {
+    cfg!(target_os = "linux")
+        && e.os_error().is_some_and(|code| {
+            std::io::Error::from_raw_os_error(code as i32).kind() == std::io::ErrorKind::NotFound
+        })
+}
+
 async fn list_devices(error_prefix: &'static str) -> Result<Vec<nusb::DeviceInfo>> {
-    run_blocking(move || {
-        nusb::list_devices()
-            .wait()
-            .map(|devices| devices.collect::<Vec<_>>())
-            .map_err(|e| format!("{error_prefix} error: {e}"))
+    run_blocking(move || match nusb::list_devices().wait() {
+        Ok(devices) => Ok(devices.collect::<Vec<_>>()),
+        Err(e) if is_missing_usb_bus(&e) => Ok(Vec::new()),
+        Err(e) => Err(format!("{error_prefix} error: {e}")),
     })
     .await
 }

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));
         }
     }