fix: kill subscription child processes on drop

pactl subscribe (volume) and playerctl --follow (media) child processes
were never terminated when their subscription ended, leaking one orphan
per reload and eventually exhausting the pulse client limit.

Author: Qiumix

src/modules/media.rs

@@ -27,7 +27,7 @@ use crate::{
 };
 use crate::{impl_on_click, impl_wrapper};
 
-use super::Module;
+use super::{KillOnDrop, Module};
 
 #[derive(Debug, Builder)]
 pub struct MediaMod {
@@ -493,6 +493,10 @@ impl Module for MediaMod {
                     .take()
                     .expect("child did not have a handle to stdout");
 
+                // Kill playerctl when the subscription ends (e.g. on reload),
+                // so it doesn't leak and accumulate processes.
+                let _kill_on_drop = KillOnDrop(child);
+
                 let mut reader = BufReader::new(stdout).lines();
                 let mut last_track = String::new();
 

src/modules/mod.rs

@@ -160,6 +160,17 @@ pub trait Module: Any + Debug + Send + Sync + Downcast {
 }
 impl_downcast!(Module);
 
+/// Kills the wrapped child process when dropped, so subscription child
+/// processes (e.g. `pactl subscribe`, `playerctl --follow`) don't leak when
+/// the subscription ends (e.g. on config reload).
+pub struct KillOnDrop(pub tokio::process::Child);
+
+impl Drop for KillOnDrop {
+    fn drop(&mut self) {
+        let _ = self.0.start_kill();
+    }
+}
+
 pub trait Action: Any + Debug + Send + Sync + Downcast {
     fn as_message(&self) -> Message;
 }

src/modules/volume.rs

@@ -21,7 +21,7 @@ use crate::{
 };
 use crate::{impl_on_click, impl_wrapper};
 
-use super::Module;
+use super::{KillOnDrop, Module};
 
 #[derive(Default, Debug, Builder)]
 pub struct VolumeMod {
@@ -109,6 +109,10 @@ impl Module for VolumeMod {
                     .take()
                     .expect("child did not have a handle to stdout");
 
+                // Kill pactl when the subscription ends (e.g. on reload), so
+                // it doesn't leak and exhaust the pulse client limit.
+                let _kill_on_drop = KillOnDrop(child);
+
                 let mut reader = BufReader::new(stdout).lines();
 
                 while let Some(line) = reader.next_line().await.unwrap() {