From fc213f1c26ed65410214f6678600a84090eb6a8f Mon Sep 17 00:00:00 2001
From: Lukas Wirth <lukas@zed.dev>
Date: Fri, 28 Nov 2025 08:46:09 +0100
Subject: [PATCH] git_ui: Introduce explicit yield points for project diff
 (#43706)

These are long running foreground tasks that tend to not have pending
await points, meaning once we start executing them they will never
reschedule themselves, starving the foreground thread.

Release Notes:

- Improved git project diff responsiveness
---
 Cargo.lock                        |  1 +
 crates/git_ui/Cargo.toml          |  1 +
 crates/git_ui/src/project_diff.rs |  4 ++++
 crates/project/src/git_store.rs   | 11 +++++++++++
 4 files changed, 17 insertions(+)

diff --git a/Cargo.lock b/Cargo.lock
index 082f420f11..9dc5c45f34 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -7129,6 +7129,7 @@ dependencies = [
  "serde",
  "serde_json",
  "settings",
+ "smol",
  "strum 0.27.2",
  "telemetry",
  "theme",
diff --git a/crates/git_ui/Cargo.toml b/crates/git_ui/Cargo.toml
index 326424f28d..8ac2f318e4 100644
--- a/crates/git_ui/Cargo.toml
+++ b/crates/git_ui/Cargo.toml
@@ -50,6 +50,7 @@ schemars.workspace = true
 serde.workspace = true
 serde_json.workspace = true
 settings.workspace = true
+smol.workspace = true
 strum.workspace = true
 telemetry.workspace = true
 theme.workspace = true
diff --git a/crates/git_ui/src/project_diff.rs b/crates/git_ui/src/project_diff.rs
index a6de68b789..515056bef4 100644
--- a/crates/git_ui/src/project_diff.rs
+++ b/crates/git_ui/src/project_diff.rs
@@ -32,6 +32,7 @@ use project::{
     },
 };
 use settings::{Settings, SettingsStore};
+use smol::future::yield_now;
 use std::any::{Any, TypeId};
 use std::ops::Range;
 use std::sync::Arc;
@@ -584,6 +585,9 @@ impl ProjectDiff {
 
         for (entry, path_key) in buffers_to_load.into_iter().zip(path_keys.into_iter()) {
             if let Some((buffer, diff)) = entry.load.await.log_err() {
+                // We might be lagging behind enough that all future entry.load futures are no longer pending.
+                // If that is the case, this task will never yield, starving the foreground thread of execution time.
+                yield_now().await;
                 cx.update(|window, cx| {
                     this.update(cx, |this, cx| {
                         this.register_buffer(path_key, entry.file_status, buffer, diff, window, cx)
diff --git a/crates/project/src/git_store.rs b/crates/project/src/git_store.rs
index a2efc12e52..d0888d9693 100644
--- a/crates/project/src/git_store.rs
+++ b/crates/project/src/git_store.rs
@@ -56,6 +56,7 @@ use rpc::{
 };
 use serde::Deserialize;
 use settings::WorktreeId;
+use smol::future::yield_now;
 use std::{
     cmp::Ordering,
     collections::{BTreeSet, HashSet, VecDeque},
@@ -2984,6 +2985,10 @@ impl BufferGitState {
                 );
             }
 
+            // Dropping BufferDiff can be expensive, so yield back to the event loop
+            // for a bit
+            yield_now().await;
+
             let mut new_uncommitted_diff = None;
             if let Some(uncommitted_diff) = &uncommitted_diff {
                 new_uncommitted_diff = if index_matches_head {
@@ -3005,6 +3010,10 @@ impl BufferGitState {
                 }
             }
 
+            // Dropping BufferDiff can be expensive, so yield back to the event loop
+            // for a bit
+            yield_now().await;
+
             let cancel = this.update(cx, |this, _| {
                 // This checks whether all pending stage/unstage operations
                 // have quiesced (i.e. both the corresponding write and the
@@ -3043,6 +3052,8 @@ impl BufferGitState {
                 None
             };
 
+            yield_now().await;
+
             if let Some((uncommitted_diff, new_uncommitted_diff)) =
                 uncommitted_diff.as_ref().zip(new_uncommitted_diff.clone())
             {