Fix r_task::initialize() timing issue (#566)

* Remove inaccurate `dead_code` allowance

* Add comment

* Fix timing of `r_task::initialize()`

And document some things that rely on it

crates/ark/src/interface.rs

@@ -387,7 +387,13 @@ impl RMain {
                     .or_log_error(&format!("Failed to source startup file '{file}' due to"));
             }
 
-            // Initialize support functions (after routine registration)
+            // R and ark are now set up enough to allow interrupt-time and idle-time tasks
+            // to be sent through. Idle-time tasks will be run once we enter
+            // `read_console()` for the first time. Interrupt-time tasks could be run
+            // sooner if we hit a check-interrupt before then.
+            r_task::initialize(tasks_interrupt_tx, tasks_idle_tx);
+
+            // Initialize support functions (after routine registration, after r_task initialization)
             match modules::initialize() {
                 Err(err) => {
                     log::error!("Can't load R modules: {err:?}");
@@ -405,6 +411,7 @@ impl RMain {
 
             // Populate srcrefs for namespaces already loaded in the session.
             // Namespaces of future loaded packages will be populated on load.
+            // (after r_task initialization)
             if do_resource_namespaces() {
                 if let Err(err) = resource_loaded_namespaces() {
                     log::error!("Can't populate srcrefs for loaded packages: {err:?}");
@@ -414,9 +421,6 @@ impl RMain {
             // Set up the global error handler (after support function initialization)
             errors::initialize();
 
-            // Now allow interrupt-time tasks to run
-            r_task::initialize(tasks_interrupt_tx, tasks_idle_tx);
-
             // Now that R has started (emitting any startup messages), and now that we have set
             // up all hooks and handlers, officially finish the R initialization process to
             // unblock the kernel-info request and also allow the LSP to start.

crates/ark/src/r_task.rs

@@ -232,7 +232,6 @@ where
     return result.lock().unwrap().take().unwrap();
 }
 
-#[allow(dead_code)] // Currently unused
 pub(crate) fn spawn_idle<F, Fut>(fun: F)
 where
     F: FnOnce() -> Fut + 'static + Send,
@@ -261,6 +260,8 @@ where
         return;
     }
 
+    // Note that this blocks until the channels are initialized,
+    // even though these are async tasks!
     let tasks_tx = if only_idle {
         get_tasks_idle_tx()
     } else {