Add debounce for re-querying completion documentation

crates/project/src/debounced_delay.rs

@@ -0,0 +1,49 @@
+use std::time::Duration;
+
+use futures::{channel::oneshot, FutureExt};
+use gpui::{ModelContext, Task};
+
+use crate::Project;
+
+pub struct DebouncedDelay {
+    task: Option<Task<()>>,
+    cancel_channel: Option<oneshot::Sender<()>>,
+}
+
+impl DebouncedDelay {
+    pub fn new() -> DebouncedDelay {
+        DebouncedDelay {
+            task: None,
+            cancel_channel: None,
+        }
+    }
+
+    pub fn fire_new<F>(&mut self, delay: Duration, cx: &mut ModelContext<Project>, func: F)
+    where
+        F: 'static + Send + FnOnce(&mut Project, &mut ModelContext<Project>) -> Task<()>,
+    {
+        if let Some(channel) = self.cancel_channel.take() {
+            _ = channel.send(());
+        }
+
+        let (sender, mut receiver) = oneshot::channel::<()>();
+        self.cancel_channel = Some(sender);
+
+        let previous_task = self.task.take();
+        self.task = Some(cx.spawn(move |model, mut cx| async move {
+            let mut timer = cx.background_executor().timer(delay).fuse();
+            if let Some(previous_task) = previous_task {
+                previous_task.await;
+            }
+
+            futures::select_biased! {
+                _ = receiver => return,
+                _ = timer => {}
+            }
+
+            if let Ok(task) = model.update(&mut cx, |project, cx| (func)(project, cx)) {
+                task.await;
+            }
+        }));
+    }
+}