fix(plugins): only listen to hd if a plugin is subscribed to hd events (#2529)

* fix(plugins): only listen to hd if a plugin is subscribed to hd events

* style(fmt): rustfmt

* fix(tests): give time for fs watcher to do its thing

* fix(tests): increase timeout

6 files changed, 49 insertions, 20 deletions

diff --git a/zellij-server/src/plugins/mod.rs b/zellij-server/src/plugins/mod.rs
index 55e97f031..7791880f2 100644
--- a/zellij-server/src/plugins/mod.rs
+++ b/zellij-server/src/plugins/mod.rs
@@ -5,7 +5,11 @@ mod wasm_bridge;
 mod watch_filesystem;
 mod zellij_exports;
 use log::info;
-use std::{collections::HashMap, fs, path::PathBuf};
+use std::{
+    collections::{HashMap, HashSet},
+    fs,
+    path::PathBuf,
+};
 use wasmer::Store;
 
 use crate::screen::ScreenInstruction;
@@ -14,7 +18,7 @@ use crate::{pty::PtyInstruction, thread_bus::Bus, ClientId, ServerInstruction};
 use wasm_bridge::WasmBridge;
 
 use zellij_utils::{
-    data::{Event, PluginCapabilities},
+    data::{Event, EventType, PluginCapabilities},
     errors::{prelude::*, ContextType, PluginContext},
     input::{
         command::TerminalAction,
@@ -74,6 +78,7 @@ pub enum PluginInstruction {
         String, // serialized message
         String, // serialized payload
     ),
+    PluginSubscribedToEvents(PluginId, ClientId, HashSet<EventType>),
     Exit,
 }
 
@@ -97,6 +102,9 @@ impl From<&PluginInstruction> for PluginContext {
                 PluginContext::PostMessageToPluginWorker
             },
             PluginInstruction::PostMessageToPlugin(..) => PluginContext::PostMessageToPlugin,
+            PluginInstruction::PluginSubscribedToEvents(..) => {
+                PluginContext::PluginSubscribedToEvents
+            },
         }
     }
 }
@@ -267,6 +275,17 @@ pub(crate) fn plugin_thread_main(
                 )];
                 wasm_bridge.update_plugins(updates)?;
             },
+            PluginInstruction::PluginSubscribedToEvents(_plugin_id, _client_id, events) => {
+                for event in events {
+                    if let EventType::FileSystemCreate
+                    | EventType::FileSystemRead
+                    | EventType::FileSystemUpdate
+                    | EventType::FileSystemDelete = event
+                    {
+                        wasm_bridge.start_fs_watcher_if_not_started();
+                    }
+                }
+            },
             PluginInstruction::Exit => {
                 wasm_bridge.cleanup();
                 break;
diff --git a/zellij-server/src/plugins/unit/plugin_tests.rs b/zellij-server/src/plugins/unit/plugin_tests.rs
index f15ac1262..6084c9fe9 100644
--- a/zellij-server/src/plugins/unit/plugin_tests.rs
+++ b/zellij-server/src/plugins/unit/plugin_tests.rs
@@ -553,7 +553,7 @@ pub fn can_subscribe_to_hd_events() {
         received_screen_instructions,
         ScreenInstruction::PluginBytes,
         screen_receiver,
-        3
+        2
     );
 
     let _ = plugin_thread_sender.send(PluginInstruction::AddClient(client_id));
@@ -565,12 +565,8 @@ pub fn can_subscribe_to_hd_events() {
         client_id,
         size,
     ));
-    let _ = plugin_thread_sender.send(PluginInstruction::Update(vec![(
-        None,
-        Some(client_id),
-        Event::InputReceived,
-    )])); // will be cached and sent to the plugin once it's loaded
-    std::thread::sleep(std::time::Duration::from_millis(100));
+    // extra long time because we only start the fs watcher on plugin load
+    std::thread::sleep(std::time::Duration::from_millis(5000));
     std::fs::OpenOptions::new()
         .create(true)
         .write(true)
diff --git a/zellij-server/src/plugins/wasm_bridge.rs b/zellij-server/src/plugins/wasm_bridge.rs
index 319b26cd2..0e53ce41e 100644
--- a/zellij-server/src/plugins/wasm_bridge.rs
+++ b/zellij-server/src/plugins/wasm_bridge.rs
@@ -75,13 +75,7 @@ impl WasmBridge {
         let connected_clients: Arc<Mutex<Vec<ClientId>>> = Arc::new(Mutex::new(vec![]));
         let plugin_cache: Arc<Mutex<HashMap<PathBuf, Module>>> =
             Arc::new(Mutex::new(HashMap::new()));
-        let watcher = match watch_filesystem(senders.clone(), &zellij_cwd) {
-            Ok(watcher) => Some(watcher),
-            Err(e) => {
-                log::error!("Failed to watch filesystem: {:?}", e);
-                None
-            },
-        };
+        let watcher = None;
         WasmBridge {
             connected_clients,
             plugins,
@@ -697,6 +691,17 @@ impl WasmBridge {
         }
         Ok(())
     }
+    pub fn start_fs_watcher_if_not_started(&mut self) {
+        if self.watcher.is_none() {
+            self.watcher = match watch_filesystem(self.senders.clone(), &self.zellij_cwd) {
+                Ok(watcher) => Some(watcher),
+                Err(e) => {
+                    log::error!("Failed to watch filesystem: {:?}", e);
+                    None
+                },
+            };
+        }
+    }
 }
 
 fn handle_plugin_successful_loading(senders: &ThreadSenders, plugin_id: PluginId) {
diff --git a/zellij-server/src/plugins/zellij_exports.rs b/zellij-server/src/plugins/zellij_exports.rs
index f0c7ba1b9..d4153ec8a 100644
--- a/zellij-server/src/plugins/zellij_exports.rs
+++ b/zellij-server/src/plugins/zellij_exports.rs
@@ -26,7 +26,7 @@ use zellij_utils::{
     input::{
         actions::Action,
         command::{RunCommand, RunCommandAction, TerminalAction},
-        layout::{Layout, RunPlugin, RunPluginLocation},
+        layout::Layout,
         plugins::PluginType,
     },
     serde,
@@ -146,8 +146,17 @@ impl ForeignFunctionEnv {
 fn host_subscribe(env: &ForeignFunctionEnv) {
     wasi_read_object::<HashSet<EventType>>(&env.plugin_env.wasi_env)
         .and_then(|new| {
-            env.subscriptions.lock().to_anyhow()?.extend(new);
-            Ok(())
+            env.subscriptions.lock().to_anyhow()?.extend(new.clone());
+            Ok(new)
+        })
+        .and_then(|new| {
+            env.plugin_env
+                .senders
+                .send_to_plugin(PluginInstruction::PluginSubscribedToEvents(
+                    env.plugin_env.plugin_id,
+                    env.plugin_env.client_id,
+                    new,
+                ))
         })
         .with_context(|| format!("failed to subscribe for plugin {}", env.plugin_env.name()))
         .fatal();
diff --git a/zellij-server/src/screen.rs b/zellij-server/src/screen.rs
index c81e23955..63a2b00f8 100644
--- a/zellij-server/src/screen.rs
+++ b/zellij-server/src/screen.rs
@@ -929,7 +929,6 @@ impl Screen {
             self.character_cell_size.clone(),
         );
         let mut tabs_to_close = vec![];
-        let size = self.size;
         for (tab_index, tab) in &mut self.tabs {
             if tab.has_selectable_tiled_panes() {
                 tab.render(&mut output).context(err_context)?;
diff --git a/zellij-utils/src/errors.rs b/zellij-utils/src/errors.rs
index 239cf5ab8..78468891d 100644
--- a/zellij-utils/src/errors.rs
+++ b/zellij-utils/src/errors.rs
@@ -370,6 +370,7 @@ pub enum PluginContext {
     ApplyCachedWorkerMessages,
     PostMessageToPluginWorker,
     PostMessageToPlugin,
+    PluginSubscribedToEvents,
 }
 
 /// Stack call representations corresponding to the different types of [`ClientInstruction`]s.