Sync with the plugin garbage collector when setting config

crates/nu-plugin/src/plugin/gc.rs

@@ -47,6 +47,15 @@ impl PluginGc {
         let _ = self.sender.send(PluginGcMsg::SetConfig(config));
     }
 
+    /// Ensure all GC messages have been processed
+    pub fn flush(&self) {
+        let (tx, rx) = mpsc::channel();
+        let _ = self.sender.send(PluginGcMsg::Flush(tx));
+        // This will block until the channel is dropped, which could be because the send failed, or
+        // because the GC got the message
+        let _ = rx.recv();
+    }
+
     /// Increment the number of locks held by the plugin
     pub fn increment_locks(&self, amount: i64) {
         let _ = self.sender.send(PluginGcMsg::AddLocks(amount));
@@ -83,6 +92,7 @@ impl PluginGc {
 #[derive(Debug)]
 enum PluginGcMsg {
     SetConfig(PluginGcConfig),
+    Flush(mpsc::Sender<()>),
     AddLocks(i64),
     SetDisabled(bool),
     StopTracking,
@@ -123,6 +133,11 @@ impl PluginGcState {
             PluginGcMsg::SetConfig(config) => {
                 self.config = config;
             }
+            PluginGcMsg::Flush(sender) => {
+                // Rather than sending a message, we just drop the channel, which causes the other
+                // side to disconnect equally well
+                drop(sender);
+            }
             PluginGcMsg::AddLocks(amount) => {
                 self.locks += amount;
                 if self.locks < 0 {

crates/nu-plugin/src/plugin/persistent.rs

@@ -176,6 +176,7 @@ impl RegisteredPlugin for PersistentPlugin {
             if let Some(running) = running.as_ref() {
                 // If the plugin is already running, propagate the config change to the running GC
                 running.gc.set_config(gc_config.clone());
+                running.gc.flush();
             }
         }
     }