Fix Project strong reference leaks (#22470)

Kirill Bulatov created 1 year ago

Closes https://github.com/zed-industries/zed/issues/21906

* After https://github.com/zed-industries/zed/pull/21238,
`TerminalPanel` and `Project` strong references were moved into
`Pane`-related closures, creating a cycle, that did not allow
registering project release and shutting down corresponding language
servers

* After https://github.com/zed-industries/zed/pull/22329, a special
`Editor` was created with a strong reference to the `Project` which
seemed to do nothing bad in general, but when a working Zed was running
a Zed Dev build, had the same issue with preventing language servers
from shutting down.

The latter is very odd, and seems quite dangerous, as any arbitrary
`Editor` with `Project` in it may do the same, yet it seems that we did
not store them before the way git panel does.

I have tried creating a test, yet seems that we need to initialize a lot
of Zed for it which I failed — all my attempts resulted in a single
language server being present in the `Project`'s statuses.

Release Notes:

- Fixed language servers not being released between project reopens

Change summary

crates/terminal_view/src/terminal_panel.rs | 34 ++++++++++++++++-------
1 file changed, 23 insertions(+), 11 deletions(-)

Detailed changes

crates/terminal_view/src/terminal_panel.rs

@@ -964,19 +964,23 @@ pub fn new_terminal_pane(
         pane.set_should_display_tab_bar(|_| true);
         pane.set_zoom_out_on_close(false);
 
-        let terminal_panel_for_split_check = terminal_panel.clone();
+        let split_closure_terminal_panel = terminal_panel.downgrade();
         pane.set_can_split(Some(Arc::new(move |pane, dragged_item, cx| {
             if let Some(tab) = dragged_item.downcast_ref::<DraggedTab>() {
-                let current_pane = cx.view().clone();
-                let can_drag_away =
-                    terminal_panel_for_split_check.update(cx, |terminal_panel, _| {
+                let is_current_pane = &tab.pane == cx.view();
+                let Some(can_drag_away) = split_closure_terminal_panel
+                    .update(cx, |terminal_panel, _| {
                         let current_panes = terminal_panel.center.panes();
                         !current_panes.contains(&&tab.pane)
                             || current_panes.len() > 1
-                            || (tab.pane != current_pane || pane.items_len() > 1)
-                    });
+                            || (!is_current_pane || pane.items_len() > 1)
+                    })
+                    .ok()
+                else {
+                    return false;
+                };
                 if can_drag_away {
-                    let item = if tab.pane == current_pane {
+                    let item = if is_current_pane {
                         pane.item_for_index(tab.ix)
                     } else {
                         tab.pane.read(cx).item_for_index(tab.ix)
@@ -996,7 +1000,12 @@ pub fn new_terminal_pane(
             toolbar.add_item(breadcrumbs, cx);
         });
 
+        let drop_closure_project = project.downgrade();
+        let drop_closure_terminal_panel = terminal_panel.downgrade();
         pane.set_custom_drop_handle(cx, move |pane, dropped_item, cx| {
+            let Some(project) = drop_closure_project.upgrade() else {
+                return ControlFlow::Break(());
+            };
             if let Some(tab) = dropped_item.downcast_ref::<DraggedTab>() {
                 let this_pane = cx.view().clone();
                 let item = if tab.pane == this_pane {
@@ -1009,10 +1018,10 @@ pub fn new_terminal_pane(
                         let source = tab.pane.clone();
                         let item_id_to_move = item.item_id();
 
-                        let new_split_pane = pane
+                        let Ok(new_split_pane) = pane
                             .drag_split_direction()
                             .map(|split_direction| {
-                                terminal_panel.update(cx, |terminal_panel, cx| {
+                                drop_closure_terminal_panel.update(cx, |terminal_panel, cx| {
                                     let is_zoomed = if terminal_panel.active_pane == this_pane {
                                         pane.is_zoomed()
                                     } else {
@@ -1033,9 +1042,12 @@ pub fn new_terminal_pane(
                                     anyhow::Ok(new_pane)
                                 })
                             })
-                            .transpose();
+                            .transpose()
+                        else {
+                            return ControlFlow::Break(());
+                        };
 
-                        match new_split_pane {
+                        match new_split_pane.transpose() {
                             // Source pane may be the one currently updated, so defer the move.
                             Ok(Some(new_pane)) => cx
                                 .spawn(|_, mut cx| async move {