Clean up completion tasks, even if they fail or return no results

This fixes a bug where leaving the completion task in `completion_tasks`
could cause the Copilot suggestion to not be shown due to the LSP not
successfully return a completion.

crates/editor/src/editor.rs

@@ -20,7 +20,7 @@ mod editor_tests;
 pub mod test;
 
 use aho_corasick::AhoCorasick;
-use anyhow::Result;
+use anyhow::{anyhow, Result};
 use blink_manager::BlinkManager;
 use clock::ReplicaId;
 use collections::{BTreeMap, Bound, HashMap, HashSet, VecDeque};
@@ -2352,11 +2352,7 @@ impl Editor {
         let id = post_inc(&mut self.next_completion_id);
         let task = cx.spawn_weak(|this, mut cx| {
             async move {
-                let completions = completions.await?;
+                let menu = if let Some(completions) = completions.await.log_err() {
-                if completions.is_empty() {
-                    return Ok(());
-                }
-
                     let mut menu = CompletionsMenu {
                         id,
                         initial_position: position,
@@ -2366,7 +2362,8 @@ impl Editor {
                             .map(|(id, completion)| {
                                 StringMatchCandidate::new(
                                     id,
-                                completion.label.text[completion.label.filter_range.clone()].into(),
+                                    completion.label.text[completion.label.filter_range.clone()]
+                                        .into(),
                                 )
                             })
                             .collect(),
@@ -2376,29 +2373,45 @@ impl Editor {
                         selected_item: 0,
                         list: Default::default(),
                     };
-
                     menu.filter(query.as_deref(), cx.background()).await;
+                    if menu.matches.is_empty() {
+                        None
+                    } else {
+                        Some(menu)
+                    }
+                } else {
+                    None
+                };
 
-                if let Some(this) = this.upgrade(&cx) {
+                let this = this
+                    .upgrade(&cx)
+                    .ok_or_else(|| anyhow!("editor was dropped"))?;
                 this.update(&mut cx, |this, cx| {
+                    this.completion_tasks.retain(|(task_id, _)| *task_id > id);
+
                     match this.context_menu.as_ref() {
                         None => {}
                         Some(ContextMenu::Completions(prev_menu)) => {
-                                if prev_menu.id > menu.id {
+                            if prev_menu.id > id {
                                 return;
                             }
                         }
                         _ => return,
                     }
 
-                        this.completion_tasks.retain(|(id, _)| *id > menu.id);
+                    if this.focused && menu.is_some() {
-                        if this.focused && !menu.matches.is_empty() {
+                        let menu = menu.unwrap();
                         this.show_context_menu(ContextMenu::Completions(menu), cx);
-                        } else if this.hide_context_menu(cx).is_none() {
+                    } else if this.completion_tasks.is_empty() {
+                        // If there are no more completion tasks and the last menu was
+                        // empty, we should hide it. If it was already hidden, we should
+                        // also show the copilot suggestion when available.
+                        if this.hide_context_menu(cx).is_none() {
                             this.update_visible_copilot_suggestion(cx);
                         }
-                    });
                     }
+                });
+
                 Ok::<_, anyhow::Error>(())
             }
             .log_err()