From fc970d188e9eeca02bc189bbcc0082a0bbf13a57 Mon Sep 17 00:00:00 2001
From: Aleksey Kladov <aleksey.kladov@gmail.com>
Date: Thu, 5 Mar 2020 12:42:04 +0100
Subject: [PATCH] Prime open files on load

---
 crates/ra_ide/src/lib.rs              |  5 +++++
 crates/ra_ide/src/prime_caches.rs     | 15 +++++++++++++++
 crates/rust-analyzer/src/main_loop.rs |  5 +++++
 3 files changed, 25 insertions(+)
 create mode 100644 crates/ra_ide/src/prime_caches.rs

diff --git a/crates/ra_ide/src/lib.rs b/crates/ra_ide/src/lib.rs
index 5a41f702ef..4dfe0553e1 100644
--- a/crates/ra_ide/src/lib.rs
+++ b/crates/ra_ide/src/lib.rs
@@ -13,6 +13,7 @@
 pub mod mock_analysis;
 mod source_change;
 
+mod prime_caches;
 mod status;
 mod completion;
 mod runnables;
@@ -227,6 +228,10 @@ impl Analysis {
         self.with_db(|db| status::status(&*db))
     }
 
+    pub fn prime_caches(&self, files: Vec<FileId>) -> Cancelable<()> {
+        self.with_db(|db| prime_caches::prime_caches(db, files))
+    }
+
     /// Gets the text of the source file.
     pub fn file_text(&self, file_id: FileId) -> Cancelable<Arc<String>> {
         self.with_db(|db| db.file_text(file_id))
diff --git a/crates/ra_ide/src/prime_caches.rs b/crates/ra_ide/src/prime_caches.rs
new file mode 100644
index 0000000000..628c989bfc
--- /dev/null
+++ b/crates/ra_ide/src/prime_caches.rs
@@ -0,0 +1,15 @@
+//! rust-analyzer is lazy and doesn't not compute anything unless asked. This
+//! sometimes is counter productive when, for example, the first goto definition
+//! request takes longer to compute. This modules implemented prepopulating of
+//! various caches, it's not really advanced at the moment.
+
+use hir::Semantics;
+
+use crate::{FileId, RootDatabase};
+
+pub(crate) fn prime_caches(db: &RootDatabase, files: Vec<FileId>) {
+    let sema = Semantics::new(db);
+    for file in files {
+        let _ = sema.to_module_def(file);
+    }
+}
diff --git a/crates/rust-analyzer/src/main_loop.rs b/crates/rust-analyzer/src/main_loop.rs
index fe804aadaa..580ad1f2c8 100644
--- a/crates/rust-analyzer/src/main_loop.rs
+++ b/crates/rust-analyzer/src/main_loop.rs
@@ -426,6 +426,11 @@ fn loop_turn(
             show_message(req::MessageType::Info, msg, &connection.sender);
         }
         world_state.check_watcher.update();
+        pool.execute({
+            let subs = loop_state.subscriptions.subscriptions();
+            let snap = world_state.snapshot();
+            move || snap.analysis().prime_caches(subs).unwrap_or_else(|_: Canceled| ())
+        });
     }
 
     if state_changed {