Fix a deserialization error with workspace events

src/con.rs

@@ -7,13 +7,16 @@ use std::os::unix::net::UnixStream;
 
 pub fn get_tree() -> ipc::Node {
     let output = util::swaymsg(&["-t", "get_tree"]);
-    let result = serde_json::from_str(output.as_str());
+    let json = output.as_str();
+    let result = serde_json::from_str(json);
 
     match result {
         Ok(node) => node,
-        Err(e) => {
-            eprintln!("Error: {}", e);
-            panic!()
+        Err(err) => {
+            panic!(
+                "Can't read get_tree response: {}\nThe JSON is: {}",
+                err, json
+            );
         }
     }
 }

src/demon.rs

@@ -23,8 +23,9 @@ pub fn monitor_window_events(
         .spawn()
         .expect("Failed to subscribe to window events");
     let stdout: proc::ChildStdout = child.stdout.unwrap();
-    let stream = Deserializer::from_reader(stdout).into_iter::<ipc::ConEvent>();
-    for res in stream {
+    let reader = std::io::BufReader::new(stdout);
+    let deserializer = Deserializer::from_reader(reader);
+    for res in deserializer.into_iter::<ipc::ConEvent>() {
         match res {
             Ok(win_ev) => handle_con_event(win_ev, con_props.clone()),
             Err(err) => eprintln!("Error handling window event:\n{:?}", err),

src/ipc.rs

@@ -230,7 +230,8 @@ pub enum ConEvent {
     WorkspaceEvent {
         change: WorkspaceEventType,
         current: Box<Node>,
-        old: Box<Node>,
+        // If the old was empty, it'll be killed => "old": null
+        old: Option<Box<Node>>,
     },
 }