Fix double read panic in nav history (#22754)

Cole Miller created 1 year ago

This one seems to be triggered when the assistant's
`View<ContextEditor>` is leased during the call into
`NavHistory::for_each_entry`, which then tries to read it again through
the `ItemHandle` interface. Fix it by skipping entries that can't be
read in the history iteration.

Release Notes:

- N/A

Change summary

crates/assistant/src/assistant_panel.rs |  4 ++++
crates/workspace/src/item.rs            |  9 +++++++++
crates/workspace/src/pane.rs            | 10 ++++++++--
crates/workspace/src/workspace.rs       |  6 ++++--
4 files changed, 25 insertions(+), 4 deletions(-)

Detailed changes

crates/assistant/src/assistant_panel.rs

@@ -4272,6 +4272,10 @@ impl Item for ContextEditor {
             None
         }
     }
+
+    fn include_in_nav_history() -> bool {
+        false
+    }
 }
 
 impl SearchableItem for ContextEditor {

crates/workspace/src/item.rs

@@ -320,6 +320,10 @@ pub trait Item: FocusableView + EventEmitter<Self::Event> {
     fn preserve_preview(&self, _cx: &AppContext) -> bool {
         false
     }
+
+    fn include_in_nav_history() -> bool {
+        true
+    }
 }
 
 pub trait SerializableItem: Item {
@@ -464,6 +468,7 @@ pub trait ItemHandle: 'static + Send {
     fn downgrade_item(&self) -> Box<dyn WeakItemHandle>;
     fn workspace_settings<'a>(&self, cx: &'a AppContext) -> &'a WorkspaceSettings;
     fn preserve_preview(&self, cx: &AppContext) -> bool;
+    fn include_in_nav_history(&self) -> bool;
 }
 
 pub trait WeakItemHandle: Send + Sync {
@@ -877,6 +882,10 @@ impl<T: Item> ItemHandle for View<T> {
     fn preserve_preview(&self, cx: &AppContext) -> bool {
         self.read(cx).preserve_preview(cx)
     }
+
+    fn include_in_nav_history(&self) -> bool {
+        T::include_in_nav_history()
+    }
 }
 
 impl From<Box<dyn ItemHandle>> for AnyView {

crates/workspace/src/pane.rs

@@ -3095,8 +3095,14 @@ impl Render for Pane {
 
 impl ItemNavHistory {
     pub fn push<D: 'static + Send + Any>(&mut self, data: Option<D>, cx: &mut WindowContext) {
-        self.history
-            .push(data, self.item.clone(), self.is_preview, cx);
+        if self
+            .item
+            .upgrade()
+            .is_some_and(|item| item.include_in_nav_history())
+        {
+            self.history
+                .push(data, self.item.clone(), self.is_preview, cx);
+        }
     }
 
     pub fn pop_backward(&mut self, cx: &mut WindowContext) -> Option<NavigationEntry> {

crates/workspace/src/workspace.rs

@@ -2975,13 +2975,15 @@ impl Workspace {
         match target {
             Some(ActivateInDirectionTarget::Pane(pane)) => cx.focus_view(&pane),
             Some(ActivateInDirectionTarget::Dock(dock)) => {
-                dock.update(cx, |dock, cx| {
+                // Defer this to avoid a panic when the dock's active panel is already on the stack.
+                cx.defer(move |cx| {
+                    let dock = dock.read(cx);
                     if let Some(panel) = dock.active_panel() {
                         panel.focus_handle(cx).focus(cx);
                     } else {
                         log::error!("Could not find a focus target when in switching focus in {direction} direction for a {:?} dock", dock.position());
                     }
-                });
+                })
             }
             None => {}
         }