python: Fix flickering in the status bar (#36039)

- **util: Have maybe! use async closures instead of async blocks**
- **python: Fix flickering of virtual environment indicator in status
bar**

Closes #30723

Release Notes:

- Python: Fixed flickering of the status bar virtual environment
indicator

---------

Co-authored-by: Lukas Wirth <lukas@zed.dev>

crates/toolchain_selector/src/active_toolchain.rs

@@ -8,6 +8,7 @@ use gpui::{
 use language::{Buffer, BufferEvent, LanguageName, Toolchain};
 use project::{Project, ProjectPath, WorktreeId, toolchain_store::ToolchainStoreEvent};
 use ui::{Button, ButtonCommon, Clickable, FluentBuilder, LabelSize, SharedString, Tooltip};
+use util::maybe;
 use workspace::{StatusItemView, Workspace, item::ItemHandle};
 
 use crate::ToolchainSelector;
@@ -55,6 +56,7 @@ impl ActiveToolchain {
     }
     fn spawn_tracker_task(window: &mut Window, cx: &mut Context<Self>) -> Task<Option<()>> {
         cx.spawn_in(window, async move |this, cx| {
+            let did_set_toolchain = maybe!(async {
                 let active_file = this
                     .read_with(cx, |this, _| {
                         this.active_buffer
@@ -92,12 +94,23 @@ impl ActiveToolchain {
                     .flatten()?;
                 let toolchain =
                     Self::active_toolchain(workspace, worktree_id, path, language_name, cx).await?;
-            let _ = this.update(cx, |this, cx| {
+                this.update(cx, |this, cx| {
                     this.active_toolchain = Some(toolchain);
 
                     cx.notify();
-            });
+                })
-            Some(())
+                .ok()
+            })
+            .await
+            .is_some();
+            if !did_set_toolchain {
+                this.update(cx, |this, cx| {
+                    this.active_toolchain = None;
+                    cx.notify();
+                })
+                .ok();
+            }
+            did_set_toolchain.then_some(())
         })
     }
 
@@ -110,6 +123,17 @@ impl ActiveToolchain {
         let editor = editor.read(cx);
         if let Some((_, buffer, _)) = editor.active_excerpt(cx) {
             if let Some(worktree_id) = buffer.read(cx).file().map(|file| file.worktree_id(cx)) {
+                if self
+                    .active_buffer
+                    .as_ref()
+                    .is_some_and(|(old_worktree_id, old_buffer, _)| {
+                        (old_worktree_id, old_buffer.entity_id())
+                            == (&worktree_id, buffer.entity_id())
+                    })
+                {
+                    return;
+                }
+
                 let subscription = cx.subscribe_in(
                     &buffer,
                     window,
@@ -231,7 +255,6 @@ impl StatusItemView for ActiveToolchain {
         cx: &mut Context<Self>,
     ) {
         if let Some(editor) = active_pane_item.and_then(|item| item.downcast::<Editor>()) {
-            self.active_toolchain.take();
             self.update_lister(editor, window, cx);
         }
         cx.notify();

crates/util/src/util.rs

@@ -887,10 +887,10 @@ macro_rules! maybe {
         (|| $block)()
     };
     (async $block:block) => {
-        (|| async $block)()
+        (async || $block)()
     };
     (async move $block:block) => {
-        (|| async move $block)()
+        (async move || $block)()
     };
 }