From a86f7a494acdb159ee471849fa7ae8f8fced79ad Mon Sep 17 00:00:00 2001
From: Myriad-Dreamin <35292584+Myriad-Dreamin@users.noreply.github.com>
Date: Wed, 11 Dec 2024 14:05:52 +0800
Subject: [PATCH] perf: prefetch package index for completion (#983)

---
 crates/tinymist-world/src/package.rs |  5 +++++
 crates/tinymist/src/server.rs        | 10 ++++++++++
 2 files changed, 15 insertions(+)

diff --git a/crates/tinymist-world/src/package.rs b/crates/tinymist-world/src/package.rs
index 06ee6aade..83c83e34b 100644
--- a/crates/tinymist-world/src/package.rs
+++ b/crates/tinymist-world/src/package.rs
@@ -218,6 +218,11 @@ impl PackageStorage {
         }
     }
 
+    /// Get the cached package index without network access.
+    pub fn cached_index(&self) -> Option<&[(PackageSpec, Option<EcoString>)]> {
+        self.index.get().map(Vec::as_slice)
+    }
+
     /// Download the package index. The result of this is cached for efficiency.
     pub fn download_index(&self) -> &[(PackageSpec, Option<EcoString>)] {
         self.index.get_or_init(|| {
diff --git a/crates/tinymist/src/server.rs b/crates/tinymist/src/server.rs
index 680b6325c..38a7b5dda 100644
--- a/crates/tinymist/src/server.rs
+++ b/crates/tinymist/src/server.rs
@@ -1069,6 +1069,16 @@ impl LanguageState {
             }
             fut_stat.stat.snap();
 
+            if matches!(query, Completion(..)) {
+                // Prefetch the package index for completion.
+                if snap.world.registry.cached_index().is_none() {
+                    let registry = snap.world.registry.clone();
+                    tokio::spawn(async move {
+                        let _ = registry.download_index();
+                    });
+                }
+            }
+
             match query {
                 SemanticTokensFull(req) => snap.run_semantic(req, R::SemanticTokensFull),
                 SemanticTokensDelta(req) => snap.run_semantic(req, R::SemanticTokensDelta),