From 0aab6d8bdc8ede886cd8f6c746ca8fc16c05c92f Mon Sep 17 00:00:00 2001
From: Conrad Irwin <conrad.irwin@gmail.com>
Date: Mon, 6 May 2024 09:46:30 -0600
Subject: [PATCH] Fix race condition in editor show_hover (#11441)

The DisplayPoint returned from the position map is only valid at the
snapshot in the position map.

Before this change we were erroneously using it to index into the
current version of the buffer.

Release Notes:

- Fixed a panic caused by a race condition in hover.
---
 crates/editor/src/element.rs       |  2 +-
 crates/editor/src/hover_popover.rs | 26 +++++++++++++++++++-------
 2 files changed, 20 insertions(+), 8 deletions(-)

diff --git a/crates/editor/src/element.rs b/crates/editor/src/element.rs
index c5fed1fdf4ffec9976ac119f41a0a83f49ee703c..70f8e2566c937553df9695508eef49c47aa2ce7c 100644
--- a/crates/editor/src/element.rs
+++ b/crates/editor/src/element.rs
@@ -638,7 +638,7 @@ impl EditorElement {
             editor.update_hovered_link(point_for_position, &position_map.snapshot, modifiers, cx);
 
             if let Some(point) = point_for_position.as_valid() {
-                hover_at(editor, Some(point), cx);
+                hover_at(editor, Some((point, &position_map.snapshot)), cx);
                 Self::update_visible_cursor(editor, point, position_map, cx);
             } else {
                 hover_at(editor, None, cx);
diff --git a/crates/editor/src/hover_popover.rs b/crates/editor/src/hover_popover.rs
index 97ee81ff81703910f435f5678c280a0aadc50e93..0133b7203251747948f5024927ec68bbfa6c4528 100644
--- a/crates/editor/src/hover_popover.rs
+++ b/crates/editor/src/hover_popover.rs
@@ -31,15 +31,20 @@ pub const HOVER_POPOVER_GAP: Pixels = px(10.);
 /// Bindable action which uses the most recent selection head to trigger a hover
 pub fn hover(editor: &mut Editor, _: &Hover, cx: &mut ViewContext<Editor>) {
     let head = editor.selections.newest_display(cx).head();
-    show_hover(editor, head, true, cx);
+    let snapshot = editor.snapshot(cx);
+    show_hover(editor, head, &snapshot, true, cx);
 }
 
 /// The internal hover action dispatches between `show_hover` or `hide_hover`
 /// depending on whether a point to hover over is provided.
-pub fn hover_at(editor: &mut Editor, point: Option<DisplayPoint>, cx: &mut ViewContext<Editor>) {
+pub fn hover_at(
+    editor: &mut Editor,
+    point: Option<(DisplayPoint, &EditorSnapshot)>,
+    cx: &mut ViewContext<Editor>,
+) {
     if EditorSettings::get_global(cx).hover_popover_enabled {
-        if let Some(point) = point {
-            show_hover(editor, point, false, cx);
+        if let Some((point, snapshot)) = point {
+            show_hover(editor, point, snapshot, false, cx);
         } else {
             hide_hover(editor, cx);
         }
@@ -160,6 +165,7 @@ pub fn hide_hover(editor: &mut Editor, cx: &mut ViewContext<Editor>) -> bool {
 fn show_hover(
     editor: &mut Editor,
     point: DisplayPoint,
+    snapshot: &EditorSnapshot,
     ignore_timeout: bool,
     cx: &mut ViewContext<Editor>,
 ) {
@@ -167,7 +173,6 @@ fn show_hover(
         return;
     }
 
-    let snapshot = editor.snapshot(cx);
     let multibuffer_offset = point.to_offset(&snapshot.display_snapshot, Bias::Left);
 
     let (buffer, buffer_position) = if let Some(output) = editor
@@ -234,6 +239,7 @@ fn show_hover(
             return;
         }
     }
+    let snapshot = snapshot.clone();
 
     let task = cx.spawn(|this, mut cx| {
         async move {
@@ -659,7 +665,10 @@ mod tests {
             fn test() { printˇln!(); }
         "});
 
-        cx.update_editor(|editor, cx| hover_at(editor, Some(hover_point), cx));
+        cx.update_editor(|editor, cx| {
+            let snapshot = editor.snapshot(cx);
+            hover_at(editor, Some((hover_point, &snapshot)), cx)
+        });
         assert!(!cx.editor(|editor, _| editor.hover_state.visible()));
 
         // After delay, hover should be visible.
@@ -705,7 +714,10 @@ mod tests {
         let mut request = cx
             .lsp
             .handle_request::<lsp::request::HoverRequest, _, _>(|_, _| async move { Ok(None) });
-        cx.update_editor(|editor, cx| hover_at(editor, Some(hover_point), cx));
+        cx.update_editor(|editor, cx| {
+            let snapshot = editor.snapshot(cx);
+            hover_at(editor, Some((hover_point, &snapshot)), cx)
+        });
         cx.background_executor
             .advance_clock(Duration::from_millis(HOVER_DELAY_MILLIS + 100));
         request.next().await;