Handle empty lines in hidutil output

src/hid.rs

@@ -44,6 +44,12 @@ fn parse_hidutil_output(mut output: &str) -> Result<Vec<Device>> {
     output = &output[line.len() + 1..];
 
     while !output.is_empty() {
+        // skip over any leading newlines
+        if output.starts_with("\n") {
+            output = &output[1..];
+            continue;
+        }
+
         let mut line_end = 0;
 
         // parse the line into a map of header -> value using the header
@@ -297,4 +303,30 @@ UserDevice    1
             ]
         );
     }
+
+    #[test]
+    fn test_parse_hidutil_output_empty_line() {
+        let output = r#"Services:
+VendorID ProductID LocationID UsagePage Usage RegistryID  Transport Class
+
+
+
+Devices:
+VendorID ProductID Product             Built-In
+0x0      0x0       BTM                 (null)
+
+
+
+"#;
+
+        let devices = parse_hidutil_output(output).unwrap();
+        assert_eq!(
+            devices,
+            vec![Device {
+                vendor_id: 0,
+                product_id: 0,
+                name: "BTM".to_owned()
+            }]
+        );
+    }
 }