file_finder: Fix auto-jump to wrong file on hover via new set_hovered_index hook (#61716)

# Objective

- Fixes #54158 

## Solution

- The root cause is in `FileFinderDelegate::set_selected_index`: it
always sets `has_changed_selected_index = true`, regardless of whether
the selection change was triggered by keyboard navigation or mouse
hover.
- Fix: Added a separate `set_hovered_index` hook to the `PickerDelegate`
trait with a default implementation that delegates to
`set_selected_index`. The hover handler in Picker now calls
`set_hovered_index` instead of `set_selected_index`. FileFinderDelegate
overrides `set_hovered_index` to update `selected_index` without setting
`has_changed_selected_index`, so hover-triggered selection changes no
longer interfere with the `Cmd+P` auto-confirm logic.

## Testing

- Added `test_hover_does_not_set_has_changed_selected_index` in
`file_finder_tests.rs`

## Self-Review Checklist:

- [x] I've reviewed my own diff for quality, security, and reliability
- [x] Unsafe blocks (if any) have justifying comments
- [x] The content adheres to Zed's UI standards
([UX/UI](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
and
[icon](https://github.com/zed-industries/zed/blob/main/crates/icons/README.md)
guidelines)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

---

Release Notes:

- Fixed file finder auto-jumping to the wrong file when the mouse
hovered over a different entry after pressing `Cmd+P`

crates/file_finder/src/file_finder.rs

@@ -1847,6 +1847,11 @@ impl PickerDelegate for FileFinderDelegate {
         self.selected_index
     }
 
+    fn set_hovered_index(&mut self, ix: usize, _: &mut Window, cx: &mut Context<Picker<Self>>) {
+        self.selected_index = ix;
+        cx.notify();
+    }
+
     fn set_selected_index(&mut self, ix: usize, _: &mut Window, cx: &mut Context<Picker<Self>>) {
         self.has_changed_selected_index = true;
         self.selected_index = ix;

crates/file_finder/src/file_finder_tests.rs

@@ -5186,3 +5186,64 @@ async fn test_exact_filename_with_directory_token(cx: &mut TestAppContext) {
         );
     });
 }
+
+#[gpui::test]
+async fn test_hover_does_not_set_has_changed_selected_index(cx: &mut TestAppContext) {
+    let app_state = init_test(cx);
+
+    app_state
+        .fs
+        .as_fake()
+        .insert_tree(
+            path!("/root"),
+            json!({
+                "a.rs": "",
+                "b.rs": "",
+            }),
+        )
+        .await;
+
+    let project = Project::test(app_state.fs.clone(), [path!("/root").as_ref()], cx).await;
+    let (multi_workspace, cx) =
+        cx.add_window_view(|window, cx| MultiWorkspace::test_new(project, window, cx));
+    let workspace = multi_workspace.read_with(cx, |mw, _| mw.workspace().clone());
+
+    open_close_queried_buffer("a", 1, "a.rs", &workspace, cx).await;
+    open_close_queried_buffer("b", 1, "b.rs", &workspace, cx).await;
+
+    let picker = open_file_picker(&workspace, cx);
+
+    picker.update(cx, |picker, _| {
+        assert!(
+            picker.delegate.matches.len() >= 2,
+            "need at least 2 matches"
+        );
+    });
+
+    picker.update_in(cx, |picker, window, cx| {
+        picker.set_hovered_index(1, window, cx);
+    });
+
+    picker.update(cx, |picker, _| {
+        assert!(
+            !picker.delegate.has_changed_selected_index,
+            "hover should not set `has_changed_selected_index`"
+        );
+        assert_eq!(
+            picker.delegate.selected_index(),
+            1,
+            "hover should change `selected_index`"
+        );
+    });
+
+    picker.update_in(cx, |picker, window, cx| {
+        picker.cycle_selection(window, cx);
+    });
+
+    picker.update(cx, |picker, _| {
+        assert!(
+            picker.delegate.has_changed_selected_index,
+            "keyboard should set `has_changed_selected_index`"
+        );
+    });
+}

crates/picker/src/picker.rs

@@ -172,6 +172,14 @@ pub trait PickerDelegate: Sized + 'static {
     fn separators_after_indices(&self) -> Vec<usize> {
         Vec::new()
     }
+    fn set_hovered_index(
+        &mut self,
+        ix: usize,
+        window: &mut Window,
+        cx: &mut Context<Picker<Self>>,
+    ) {
+        self.set_selected_index(ix, window, cx);
+    }
     fn set_selected_index(
         &mut self,
         ix: usize,
@@ -797,6 +805,32 @@ impl<D: PickerDelegate> Picker<D> {
         self.focus_handle(cx).focus(window, cx);
     }
 
+    pub fn set_hovered_index(&mut self, ix: usize, window: &mut Window, cx: &mut Context<Self>) {
+        let match_count = self.delegate.match_count();
+        if match_count == 0 {
+            return;
+        }
+
+        if !self.delegate.can_select(ix, window, cx) {
+            return;
+        }
+
+        let previous_index = self.delegate.selected_index();
+        self.delegate.set_hovered_index(ix, window, cx);
+        let current_index = self.delegate.selected_index();
+
+        if previous_index != current_index {
+            if let Some(action) = self.delegate.selected_index_changed(ix, window, cx) {
+                action(window, cx);
+            }
+            if let Some(preview) = &mut self.preview
+                && let Some(update) = self.delegate.try_get_preview_data_for_match(cx)
+            {
+                preview.update(update, window, cx);
+            }
+        }
+    }
+
     /// Handles the selecting an index, and passing the change to the delegate.
     /// If `fallback_direction` is set to `None`, the index will not be selected
     /// if the element at that index cannot be selected.
@@ -1414,7 +1448,7 @@ impl<D: PickerDelegate> Picker<D> {
             .when(self.delegate.select_on_hover(), |this| {
                 this.on_hover(cx.listener(move |this, hovered: &bool, window, cx| {
                     if *hovered {
-                        this.set_selected_index(ix, None, false, window, cx);
+                        this.set_hovered_index(ix, window, cx);
                         cx.notify();
                     }
                 }))