fix(ui): wait until task output is fully rendered on stop (#8588)

### Description

Previously we weren't `app.stop()` would exit before the TUI cleanup
completed. This resulted in a race condition between the TUI cleanup and
the run summary getting printed.

This PR changes the call to now wait until cleanup completes before
returning ensuring that the run summary is written only after the TUI
exits.

### Testing Instructions

Run a task a few times and you should see the run summary either not get
rendered *or* getting rendered before the terminal is back in cooked
mode.

Before:
<img width="1106" alt="Screenshot 2024-06-24 at 12 13 12 PM"
src="https://github.com/vercel/turbo/assets/4131117/6fc678c3-36a8-4526-bd22-289aa5f1ca94">
After:
<img width="759" alt="Screenshot 2024-06-24 at 12 09 20 PM"
src="https://github.com/vercel/turbo/assets/4131117/8cb93df6-3310-4047-b460-30ab10e40df2">

crates/turborepo-ui/src/tui/app.rs

@@ -1,5 +1,6 @@
 use std::{
  io::{self, Stdout, Write},
+ sync::mpsc,
  time::{Duration, Instant},
 };
 
@@ -120,9 +121,12 @@ pub fn run_app(tasks: Vec<String>, receiver: AppReceiver) -> Result<(), Error> {
  let mut app: App<Box<dyn io::Write + Send>> =
  App::new(size.height, full_task_width.max(ratio_pane_width), tasks);
 
- let result = run_app_inner(&mut terminal, &mut app, receiver);
+ let (result, callback) = match run_app_inner(&mut terminal, &mut app, receiver) {
+ Ok(callback) => (Ok(()), callback),
+ Err(err) => (Err(err), None),
+ };
 
- cleanup(terminal, app)?;
+ cleanup(terminal, app, callback)?;
 
  result
 }
@@ -133,12 +137,13 @@ fn run_app_inner<B: Backend + std::io::Write>(
  terminal: &mut Terminal<B>,
  app: &mut App<Box<dyn io::Write + Send>>,
  receiver: AppReceiver,
-) -> Result<(), Error> {
+) -> Result<Option<mpsc::SyncSender<()>>, Error> {
  // Render initial state to paint the screen
  terminal.draw(|f| view(app, f))?;
  let mut last_render = Instant::now();
+ let mut callback = None;
  while let Some(event) = poll(app.input_options, &receiver, last_render + FRAMERATE) {
- update(app, event)?;
+ callback = update(app, event)?;
  if app.done {
  break;
  }
@@ -148,7 +153,7 @@ fn run_app_inner<B: Backend + std::io::Write>(
  }
  }
 
- Ok(())
+ Ok(callback)
 }
 
 /// Blocking poll for events, will only return None if app handle has been
@@ -158,7 +163,7 @@ fn poll(input_options: InputOptions, receiver: &AppReceiver, deadline: Instant)
  Ok(Some(event)) => Some(event),
  Ok(None) => receiver.recv(deadline).ok(),
  // Unable to read from stdin, shut down and attempt to clean up
- Err(_) => Some(Event::Stop),
+ Err(_) => Some(Event::InternalStop),
  }
 }
 
@@ -198,6 +203,7 @@ fn startup() -> io::Result<Terminal<CrosstermBackend<Stdout>>> {
 fn cleanup<B: Backend + io::Write, I>(
  mut terminal: Terminal<B>,
  mut app: App<I>,
+ callback: Option<mpsc::SyncSender<()>>,
 ) -> io::Result<()> {
  terminal.clear()?;
  crossterm::execute!(
@@ -209,13 +215,15 @@ fn cleanup<B: Backend + io::Write, I>(
  app.pane.persist_tasks(&started_tasks)?;
  crossterm::terminal::disable_raw_mode()?;
  terminal.show_cursor()?;
+ // We can close the channel now that terminal is back restored to a normal state
+ drop(callback);
  Ok(())
 }
 
 fn update(
  app: &mut App<Box<dyn io::Write + Send>>,
  event: Event,
-) -> Result<Option<Vec<u8>>, Error> {
+) -> Result<Option<mpsc::SyncSender<()>>, Error> {
  match event {
  Event::StartTask { task } => {
  app.table.start_task(&task)?;
@@ -227,8 +235,12 @@ fn update(
  Event::Status { task, status } => {
  app.pane.set_status(&task, status)?;
  }
- Event::Stop => {
+ Event::InternalStop => {
+ app.done = true;
+ }
+ Event::Stop(callback) => {
  app.done = true;
+ return Ok(Some(callback));
  }
  Event::Tick => {
  app.table.tick();

crates/turborepo-ui/src/tui/event.rs

@@ -14,7 +14,9 @@ pub enum Event {
  task: String,
  status: String,
  },
- Stop,
+ Stop(std::sync::mpsc::SyncSender<()>),
+ // Stop initiated by the TUI itself
+ InternalStop,
  Tick,
  Up,
  Down,

crates/turborepo-ui/src/tui/handle.rs

@@ -52,9 +52,12 @@ impl AppSender {
 
  /// Stop rendering TUI and restore terminal to default configuration
  pub fn stop(&self) {
+ let (callback_tx, callback_rx) = mpsc::sync_channel(1);
  // Send stop event, if receiver has dropped ignore error as
  // it'll be a no-op.
- self.primary.send(Event::Stop).ok();
+ self.primary.send(Event::Stop(callback_tx)).ok();
+ // Wait for callback to be sent or the channel closed.
+ callback_rx.recv().ok();
  }
 
  /// Update the list of tasks displayed in the TUI

crates/turborepo-ui/src/tui/input.rs

@@ -77,7 +77,7 @@ fn ctrl_c() -> Option<Event> {
  match signal::raise(signal::SIGINT) {
  Ok(_) => None,
  // We're unable to send the signal, stop rendering to force shutdown
- Err(_) => Some(Event::Stop),
+ Err(_) => Some(Event::InternalStop),
  }
 }
 
@@ -101,7 +101,7 @@ fn ctrl_c() -> Option<Event> {
  None
  } else {
  // We're unable to send the Ctrl-C event, stop rendering to force shutdown
- Some(Event::Stop)
+ Some(Event::InternalStop)
  }
 }