From 8d083a639cf42c760fe337ab4486d9f6eb55ddd1 Mon Sep 17 00:00:00 2001
From: John Tur <john-tur@outlook.com>
Date: Sat, 7 Mar 2026 20:51:22 -0500
Subject: [PATCH] Lazily initialize kernelspecs (#51026)

On Windows, the WSL VM always boots up when Zed is opened, because we
eagerly discover which jupyter kernels are installed inside WSL on
startup. This is not desirable if the REPL feature is not being used.
Defer this work to the point where we actually need to know what kernels
are installed.

Release Notes:

- N/A
---
 crates/repl/src/components/kernel_options.rs |  4 +++-
 crates/repl/src/repl_editor.rs               |  1 +
 crates/repl/src/repl_sessions_ui.rs          |  3 ++-
 crates/repl/src/repl_store.rs                | 17 ++++++++++-------
 4 files changed, 16 insertions(+), 9 deletions(-)

diff --git a/crates/repl/src/components/kernel_options.rs b/crates/repl/src/components/kernel_options.rs
index 45e55f0d5f8a17d66a76d206216c07ba7cc36e8a..b6d4f39c0ccb75619a7e4efd6a532202893c8722 100644
--- a/crates/repl/src/components/kernel_options.rs
+++ b/crates/repl/src/components/kernel_options.rs
@@ -448,7 +448,9 @@ where
     TT: Fn(&mut Window, &mut App) -> AnyView + 'static,
 {
     fn render(self, window: &mut Window, cx: &mut App) -> impl IntoElement {
-        let store = ReplStore::global(cx).read(cx);
+        let store = ReplStore::global(cx);
+        store.update(cx, |store, cx| store.ensure_kernelspecs(cx));
+        let store = store.read(cx);
 
         let all_entries = build_grouped_entries(store, self.worktree_id);
         let selected_kernelspec = store.active_kernelspec(self.worktree_id, None, cx);
diff --git a/crates/repl/src/repl_editor.rs b/crates/repl/src/repl_editor.rs
index 56b79e20ffca74ab3f9f9c7948a7caeffc4ad4ce..cf1493000edb5881bff412224f7e44dbfbf88b25 100644
--- a/crates/repl/src/repl_editor.rs
+++ b/crates/repl/src/repl_editor.rs
@@ -191,6 +191,7 @@ pub fn run(
     if !store.read(cx).is_enabled() {
         return Ok(());
     }
+    store.update(cx, |store, cx| store.ensure_kernelspecs(cx));
 
     let editor = editor.upgrade().context("editor was dropped")?;
     let selected_range = editor
diff --git a/crates/repl/src/repl_sessions_ui.rs b/crates/repl/src/repl_sessions_ui.rs
index 1dc2107adde84d4625ffee489805570cd7e5f791..9781382fc85d5da549a65dce2ca06fef4a3bff15 100644
--- a/crates/repl/src/repl_sessions_ui.rs
+++ b/crates/repl/src/repl_sessions_ui.rs
@@ -204,7 +204,8 @@ impl Render for ReplSessionsPage {
     fn render(&mut self, _: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
         let store = ReplStore::global(cx);
 
-        let (kernel_specifications, sessions) = store.update(cx, |store, _cx| {
+        let (kernel_specifications, sessions) = store.update(cx, |store, cx| {
+            store.ensure_kernelspecs(cx);
             (
                 store
                     .pure_jupyter_kernel_specifications()
diff --git a/crates/repl/src/repl_store.rs b/crates/repl/src/repl_store.rs
index ff0a2793617982e75d6c81d6c3a180d2f9b3c8ee..800bab030143de70f08ce2c020bd3095b6767e16 100644
--- a/crates/repl/src/repl_store.rs
+++ b/crates/repl/src/repl_store.rs
@@ -27,6 +27,7 @@ pub struct ReplStore {
     enabled: bool,
     sessions: HashMap<EntityId, Entity<Session>>,
     kernel_specifications: Vec<KernelSpecification>,
+    kernelspecs_initialized: bool,
     selected_kernel_for_worktree: HashMap<WorktreeId, KernelSpecification>,
     kernel_specifications_for_worktree: HashMap<WorktreeId, Vec<KernelSpecification>>,
     active_python_toolchain_for_worktree: HashMap<WorktreeId, SharedString>,
@@ -39,12 +40,6 @@ impl ReplStore {
 
     pub(crate) fn init(fs: Arc<dyn Fs>, cx: &mut App) {
         let store = cx.new(move |cx| Self::new(fs, cx));
-
-        #[cfg(not(feature = "test-support"))]
-        store
-            .update(cx, |store, cx| store.refresh_kernelspecs(cx))
-            .detach_and_log_err(cx);
-
         cx.set_global(GlobalReplStore(store))
     }
 
@@ -65,6 +60,7 @@ impl ReplStore {
             enabled: JupyterSettings::enabled(cx),
             sessions: HashMap::default(),
             kernel_specifications: Vec::new(),
+            kernelspecs_initialized: false,
             _subscriptions: subscriptions,
             kernel_specifications_for_worktree: HashMap::default(),
             selected_kernel_for_worktree: HashMap::default(),
@@ -216,10 +212,17 @@ impl ReplStore {
         }
     }
 
+    pub fn ensure_kernelspecs(&mut self, cx: &mut Context<Self>) {
+        if self.kernelspecs_initialized {
+            return;
+        }
+        self.kernelspecs_initialized = true;
+        self.refresh_kernelspecs(cx).detach_and_log_err(cx);
+    }
+
     pub fn refresh_kernelspecs(&mut self, cx: &mut Context<Self>) -> Task<Result<()>> {
         let local_kernel_specifications = local_kernel_specifications(self.fs.clone());
         let wsl_kernel_specifications = wsl_kernel_specifications(cx.background_executor().clone());
-
         let remote_kernel_specifications = self.get_remote_kernel_specifications(cx);
 
         let all_specs = cx.background_spawn(async move {