theme_selector: Preserve selected theme after empty filter (#52461)

When filtering themes with a query that matches nothing (e.g., "zzz"),
`show_selected_theme` returned `None` and overwrote `selected_theme`.
Clearing the filter then lost track of the previous selection and
defaulted to index 0.

The fix only updates `selected_theme` when `show_selected_theme` returns
`Some`. Same change in both the theme selector and the icon theme
selector.

## Context

When `update_matches` runs a filter that yields zero results,
`show_selected_theme` returns `None`. The old code unconditionally
assigned that back to `selected_theme`, wiping out the previous
selection. When the user clears the filter, the selector falls into the
`query.is_empty() && selected_theme.is_none()` branch and resets to
index 0 instead of restoring the original pick.

## Demo

### Before:


https://github.com/user-attachments/assets/62b1531b-d059-4f30-b1f4-a830f2d13a09


### After:



https://github.com/user-attachments/assets/72348666-8dbb-4f35-9446-fa2618340b6c




## How to review

The fix is the same one-line change in two files:
1. `crates/theme_selector/src/theme_selector.rs` — line 458
2. `crates/theme_selector/src/icon_theme_selector.rs` — line 272

The rest is test infrastructure:
3. `crates/theme/src/registry.rs` — `register_test_themes` /
`register_test_icon_themes` helpers
4. Tests in both selector files covering the empty filter → clear filter
flow

## 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 is consistent with the [UI/UX
checklist](https://github.com/zed-industries/zed/blob/main/CONTRIBUTING.md#uiux-checklist)
- [x] Tests cover the new/changed behavior
- [x] Performance impact has been considered and is acceptable

## Release notes

- Fixed theme selector losing the selected theme after filtering with a
query that matches nothing and then clearing the filter.

Cargo.lock

@@ -17731,12 +17731,15 @@ dependencies = [
 name = "theme_selector"
 version = "0.1.0"
 dependencies = [
+ "editor",
  "fs",
  "fuzzy",
  "gpui",
  "log",
  "picker",
+ "project",
  "serde",
+ "serde_json",
  "settings",
  "telemetry",
  "theme",

crates/theme/src/registry.rs

@@ -126,6 +126,23 @@ impl ThemeRegistry {
         }
     }
 
+    /// Registers theme families for use in tests.
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn register_test_themes(&self, families: impl IntoIterator<Item = ThemeFamily>) {
+        self.insert_theme_families(families);
+    }
+
+    /// Registers icon themes for use in tests.
+    #[cfg(any(test, feature = "test-support"))]
+    pub fn register_test_icon_themes(&self, icon_themes: impl IntoIterator<Item = IconTheme>) {
+        let mut state = self.state.write();
+        for icon_theme in icon_themes {
+            state
+                .icon_themes
+                .insert(icon_theme.name.clone(), Arc::new(icon_theme));
+        }
+    }
+
     /// Inserts the given themes into the registry.
     pub fn insert_themes(&self, themes: impl IntoIterator<Item = Theme>) {
         let mut state = self.state.write();

crates/theme_selector/Cargo.toml

@@ -29,3 +29,7 @@ workspace.workspace = true
 zed_actions.workspace = true
 
 [dev-dependencies]
+editor = { workspace = true, features = ["test-support"] }
+project.workspace = true
+serde_json.workspace = true
+theme = { workspace = true, features = ["test-support"] }

crates/theme_selector/src/icon_theme_selector.rs

@@ -267,7 +267,10 @@ impl PickerDelegate for IconThemeSelectorDelegate {
                 } else {
                     this.delegate.selected_index = 0;
                 }
-                this.delegate.selected_theme = this.delegate.show_selected_theme(cx);
+                // Preserve the previously selected theme when the filter yields no results.
+                if let Some(theme) = this.delegate.show_selected_theme(cx) {
+                    this.delegate.selected_theme = Some(theme);
+                }
             })
             .log_err();
         })
@@ -335,3 +338,158 @@ impl PickerDelegate for IconThemeSelectorDelegate {
         )
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use std::collections::HashMap;
+
+    use gpui::{TestAppContext, VisualTestContext};
+    use project::Project;
+    use serde_json::json;
+    use theme::{ChevronIcons, DirectoryIcons, IconTheme, ThemeRegistry};
+    use util::path;
+    use workspace::MultiWorkspace;
+
+    fn init_test(cx: &mut TestAppContext) -> Arc<workspace::AppState> {
+        cx.update(|cx| {
+            let app_state = workspace::AppState::test(cx);
+            settings::init(cx);
+            theme::init(theme::LoadThemes::JustBase, cx);
+            editor::init(cx);
+            crate::init(cx);
+            app_state
+        })
+    }
+
+    fn register_test_icon_themes(cx: &mut TestAppContext) {
+        cx.update(|cx| {
+            let registry = ThemeRegistry::global(cx);
+            let make_icon_theme = |name: &str, appearance: Appearance| IconTheme {
+                id: name.to_lowercase().replace(' ', "-"),
+                name: SharedString::from(name.to_string()),
+                appearance,
+                directory_icons: DirectoryIcons {
+                    collapsed: None,
+                    expanded: None,
+                },
+                named_directory_icons: HashMap::default(),
+                chevron_icons: ChevronIcons {
+                    collapsed: None,
+                    expanded: None,
+                },
+                file_icons: HashMap::default(),
+                file_stems: HashMap::default(),
+                file_suffixes: HashMap::default(),
+            };
+            registry.register_test_icon_themes([
+                make_icon_theme("Test Icons A", Appearance::Dark),
+                make_icon_theme("Test Icons B", Appearance::Dark),
+            ]);
+        });
+    }
+
+    async fn setup_test(cx: &mut TestAppContext) -> Arc<workspace::AppState> {
+        let app_state = init_test(cx);
+        register_test_icon_themes(cx);
+        app_state
+            .fs
+            .as_fake()
+            .insert_tree(path!("/test"), json!({}))
+            .await;
+        app_state
+    }
+
+    fn open_icon_theme_selector(
+        workspace: &Entity<workspace::Workspace>,
+        cx: &mut VisualTestContext,
+    ) -> Entity<Picker<IconThemeSelectorDelegate>> {
+        cx.dispatch_action(zed_actions::icon_theme_selector::Toggle {
+            themes_filter: None,
+        });
+        cx.run_until_parked();
+        workspace.update(cx, |workspace, cx| {
+            workspace
+                .active_modal::<IconThemeSelector>(cx)
+                .expect("icon theme selector should be open")
+                .read(cx)
+                .picker
+                .clone()
+        })
+    }
+
+    fn selected_theme_name(
+        picker: &Entity<Picker<IconThemeSelectorDelegate>>,
+        cx: &mut VisualTestContext,
+    ) -> String {
+        picker.read_with(cx, |picker, _| {
+            picker
+                .delegate
+                .matches
+                .get(picker.delegate.selected_index)
+                .expect("selected index should point to a match")
+                .string
+                .clone()
+        })
+    }
+
+    fn previewed_theme_name(
+        _picker: &Entity<Picker<IconThemeSelectorDelegate>>,
+        cx: &mut VisualTestContext,
+    ) -> String {
+        cx.read(|cx| {
+            ThemeSettings::get_global(cx)
+                .icon_theme
+                .name(SystemAppearance::global(cx).0)
+                .0
+                .to_string()
+        })
+    }
+
+    #[gpui::test]
+    async fn test_icon_theme_selector_preserves_selection_on_empty_filter(cx: &mut TestAppContext) {
+        let app_state = setup_test(cx).await;
+        let project = Project::test(app_state.fs.clone(), [path!("/test").as_ref()], cx).await;
+        let (multi_workspace, cx) =
+            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project.clone(), window, cx));
+        let workspace =
+            multi_workspace.read_with(cx, |multi_workspace, _| multi_workspace.workspace().clone());
+        let picker = open_icon_theme_selector(&workspace, cx);
+
+        let target_index = picker.read_with(cx, |picker, _| {
+            picker
+                .delegate
+                .matches
+                .iter()
+                .position(|m| m.string == "Test Icons A")
+                .unwrap()
+        });
+        picker.update_in(cx, |picker, window, cx| {
+            picker.set_selected_index(target_index, None, true, window, cx);
+        });
+        cx.run_until_parked();
+
+        assert_eq!(previewed_theme_name(&picker, cx), "Test Icons A");
+
+        picker.update_in(cx, |picker, window, cx| {
+            picker.update_matches("zzz".to_string(), window, cx);
+        });
+        cx.run_until_parked();
+
+        picker.update_in(cx, |picker, window, cx| {
+            picker.update_matches("".to_string(), window, cx);
+        });
+        cx.run_until_parked();
+
+        assert_eq!(
+            selected_theme_name(&picker, cx),
+            "Test Icons A",
+            "selected icon theme should be preserved after clearing an empty filter"
+        );
+        assert_eq!(
+            previewed_theme_name(&picker, cx),
+            "Test Icons A",
+            "previewed icon theme should be preserved after clearing an empty filter"
+        );
+    }
+}

crates/theme_selector/src/theme_selector.rs

@@ -455,7 +455,10 @@ impl PickerDelegate for ThemeSelectorDelegate {
                 } else {
                     this.delegate.selected_index = 0;
                 }
-                this.delegate.selected_theme = this.delegate.show_selected_theme(cx);
+                // Preserve the previously selected theme when the filter yields no results.
+                if let Some(theme) = this.delegate.show_selected_theme(cx) {
+                    this.delegate.selected_theme = Some(theme);
+                }
             })
             .log_err();
         })
@@ -523,3 +526,151 @@ impl PickerDelegate for ThemeSelectorDelegate {
         )
     }
 }
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+    use gpui::{TestAppContext, VisualTestContext};
+    use project::Project;
+    use serde_json::json;
+    use theme::{Appearance, ThemeFamily, ThemeRegistry, default_color_scales};
+    use util::path;
+    use workspace::MultiWorkspace;
+
+    fn init_test(cx: &mut TestAppContext) -> Arc<workspace::AppState> {
+        cx.update(|cx| {
+            let app_state = workspace::AppState::test(cx);
+            settings::init(cx);
+            theme::init(theme::LoadThemes::JustBase, cx);
+            editor::init(cx);
+            super::init(cx);
+            app_state
+        })
+    }
+
+    fn register_test_themes(cx: &mut TestAppContext) {
+        cx.update(|cx| {
+            let registry = ThemeRegistry::global(cx);
+            let base_theme = registry.get("One Dark").unwrap();
+
+            let mut test_light = (*base_theme).clone();
+            test_light.id = "test-light".to_string();
+            test_light.name = "Test Light".into();
+            test_light.appearance = Appearance::Light;
+
+            let mut test_dark_a = (*base_theme).clone();
+            test_dark_a.id = "test-dark-a".to_string();
+            test_dark_a.name = "Test Dark A".into();
+
+            let mut test_dark_b = (*base_theme).clone();
+            test_dark_b.id = "test-dark-b".to_string();
+            test_dark_b.name = "Test Dark B".into();
+
+            registry.register_test_themes([ThemeFamily {
+                id: "test-family".to_string(),
+                name: "Test Family".into(),
+                author: "test".into(),
+                themes: vec![test_light, test_dark_a, test_dark_b],
+                scales: default_color_scales(),
+            }]);
+        });
+    }
+
+    async fn setup_test(cx: &mut TestAppContext) -> Arc<workspace::AppState> {
+        let app_state = init_test(cx);
+        register_test_themes(cx);
+        app_state
+            .fs
+            .as_fake()
+            .insert_tree(path!("/test"), json!({}))
+            .await;
+        app_state
+    }
+
+    fn open_theme_selector(
+        workspace: &Entity<workspace::Workspace>,
+        cx: &mut VisualTestContext,
+    ) -> Entity<Picker<ThemeSelectorDelegate>> {
+        cx.dispatch_action(zed_actions::theme_selector::Toggle {
+            themes_filter: None,
+        });
+        cx.run_until_parked();
+        workspace.update(cx, |workspace, cx| {
+            workspace
+                .active_modal::<ThemeSelector>(cx)
+                .expect("theme selector should be open")
+                .read(cx)
+                .picker
+                .clone()
+        })
+    }
+
+    fn selected_theme_name(
+        picker: &Entity<Picker<ThemeSelectorDelegate>>,
+        cx: &mut VisualTestContext,
+    ) -> String {
+        picker.read_with(cx, |picker, _| {
+            picker
+                .delegate
+                .matches
+                .get(picker.delegate.selected_index)
+                .expect("selected index should point to a match")
+                .string
+                .clone()
+        })
+    }
+
+    fn previewed_theme_name(
+        picker: &Entity<Picker<ThemeSelectorDelegate>>,
+        cx: &mut VisualTestContext,
+    ) -> String {
+        picker.read_with(cx, |picker, _| picker.delegate.new_theme.name.to_string())
+    }
+
+    #[gpui::test]
+    async fn test_theme_selector_preserves_selection_on_empty_filter(cx: &mut TestAppContext) {
+        let app_state = setup_test(cx).await;
+        let project = Project::test(app_state.fs.clone(), [path!("/test").as_ref()], cx).await;
+        let (multi_workspace, cx) =
+            cx.add_window_view(|window, cx| MultiWorkspace::test_new(project.clone(), window, cx));
+        let workspace =
+            multi_workspace.read_with(cx, |multi_workspace, _| multi_workspace.workspace().clone());
+        let picker = open_theme_selector(&workspace, cx);
+
+        let target_index = picker.read_with(cx, |picker, _| {
+            picker
+                .delegate
+                .matches
+                .iter()
+                .position(|m| m.string == "Test Light")
+                .unwrap()
+        });
+        picker.update_in(cx, |picker, window, cx| {
+            picker.set_selected_index(target_index, None, true, window, cx);
+        });
+        cx.run_until_parked();
+
+        assert_eq!(previewed_theme_name(&picker, cx), "Test Light");
+
+        picker.update_in(cx, |picker, window, cx| {
+            picker.update_matches("zzz".to_string(), window, cx);
+        });
+        cx.run_until_parked();
+
+        picker.update_in(cx, |picker, window, cx| {
+            picker.update_matches("".to_string(), window, cx);
+        });
+        cx.run_until_parked();
+
+        assert_eq!(
+            selected_theme_name(&picker, cx),
+            "Test Light",
+            "selected theme should be preserved after clearing an empty filter"
+        );
+        assert_eq!(
+            previewed_theme_name(&picker, cx),
+            "Test Light",
+            "previewed theme should be preserved after clearing an empty filter"
+        );
+    }
+}