chore: fix flaky steps_output_within test (#14479)

cli/tools/test.rs

@@ -36,6 +36,7 @@ use deno_core::futures::future;
 use deno_core::futures::stream;
 use deno_core::futures::FutureExt;
 use deno_core::futures::StreamExt;
+use deno_core::parking_lot::Mutex;
 use deno_core::serde_json::json;
 use deno_core::url::Url;
 use deno_core::ModuleSpecifier;
@@ -1449,43 +1450,28 @@ pub async fn run_tests_with_watch(
   Ok(())
 }
 
+#[derive(Clone)]
 pub struct TestEventSender {
   sender: UnboundedSender<TestEvent>,
-  stdout_writer: os_pipe::PipeWriter,
-  stderr_writer: os_pipe::PipeWriter,
-}
-
-impl Clone for TestEventSender {
-  fn clone(&self) -> Self {
-    Self {
-      sender: self.sender.clone(),
-      stdout_writer: self.stdout_writer.try_clone().unwrap(),
-      stderr_writer: self.stderr_writer.try_clone().unwrap(),
-    }
-  }
+  stdout_writer: TestOutputPipe,
+  stderr_writer: TestOutputPipe,
 }
 
 impl TestEventSender {
   pub fn new(sender: UnboundedSender<TestEvent>) -> Self {
-    let (stdout_reader, stdout_writer) = os_pipe::pipe().unwrap();
-    let (stderr_reader, stderr_writer) = os_pipe::pipe().unwrap();
-
-    start_output_redirect_thread(stdout_reader, sender.clone());
-    start_output_redirect_thread(stderr_reader, sender.clone());
-
     Self {
+      stdout_writer: TestOutputPipe::new(sender.clone()),
+      stderr_writer: TestOutputPipe::new(sender.clone()),
       sender,
-      stdout_writer,
-      stderr_writer,
     }
   }
 
   pub fn stdout(&self) -> std::fs::File {
-    pipe_writer_to_file(self.stdout_writer.try_clone().unwrap())
+    self.stdout_writer.as_file()
   }
 
   pub fn stderr(&self) -> std::fs::File {
-    pipe_writer_to_file(self.stderr_writer.try_clone().unwrap())
+    self.stderr_writer.as_file()
   }
 
   pub fn send(&mut self, message: TestEvent) -> Result<(), AnyError> {
@@ -1497,13 +1483,62 @@ impl TestEventSender {
         | TestEvent::StepWait(_)
         | TestEvent::StepResult(_, _, _)
     ) {
-      self.stdout_writer.flush().unwrap();
-      self.stderr_writer.flush().unwrap();
+      self.flush_stdout_and_stderr();
     }
 
     self.sender.send(message)?;
     Ok(())
   }
+
+  fn flush_stdout_and_stderr(&mut self) {
+    self.stdout_writer.flush();
+    self.stderr_writer.flush();
+  }
+}
+
+// use a string that if it ends up in the output won't affect how things are displayed
+const ZERO_WIDTH_SPACE: &str = "\u{200B}";
+
+struct TestOutputPipe {
+  writer: os_pipe::PipeWriter,
+  state: Arc<Mutex<Option<std::sync::mpsc::Sender<()>>>>,
+}
+
+impl Clone for TestOutputPipe {
+  fn clone(&self) -> Self {
+    Self {
+      writer: self.writer.try_clone().unwrap(),
+      state: self.state.clone(),
+    }
+  }
+}
+
+impl TestOutputPipe {
+  pub fn new(sender: UnboundedSender<TestEvent>) -> Self {
+    let (reader, writer) = os_pipe::pipe().unwrap();
+    let state = Arc::new(Mutex::new(None));
+
+    start_output_redirect_thread(reader, sender, state.clone());
+
+    Self { writer, state }
+  }
+
+  pub fn flush(&mut self) {
+    // We want to wake up the other thread and have it respond back
+    // that it's done clearing out its pipe before returning.
+    let (sender, receiver) = std::sync::mpsc::channel();
+    self.state.lock().replace(sender);
+    // Bit of a hack in order to send a zero width space in order
+    // to wake the thread up. It seems that sending zero bytes
+    // does not work here on windows.
+    self.writer.write_all(ZERO_WIDTH_SPACE.as_bytes()).unwrap();
+    self.writer.flush().unwrap();
+    receiver.recv().unwrap();
+  }
+
+  pub fn as_file(&self) -> std::fs::File {
+    pipe_writer_to_file(self.writer.try_clone().unwrap())
+  }
 }
 
 #[cfg(windows)]
@@ -1525,6 +1560,7 @@ fn pipe_writer_to_file(writer: os_pipe::PipeWriter) -> std::fs::File {
 fn start_output_redirect_thread(
   mut pipe_reader: os_pipe::PipeReader,
   sender: UnboundedSender<TestEvent>,
+  flush_state: Arc<Mutex<Option<std::sync::mpsc::Sender<()>>>>,
 ) {
   tokio::task::spawn_blocking(move || loop {
     let mut buffer = [0; 512];
@@ -1532,12 +1568,24 @@ fn start_output_redirect_thread(
       Ok(0) | Err(_) => break,
       Ok(size) => size,
     };
+    let oneshot_sender = flush_state.lock().take();
+    let mut data = &buffer[0..size];
+    if data.ends_with(ZERO_WIDTH_SPACE.as_bytes()) {
+      data = &data[0..data.len() - ZERO_WIDTH_SPACE.len()];
+    }
 
-    if sender
-      .send(TestEvent::Output(buffer[0..size].to_vec()))
-      .is_err()
+    if !data.is_empty()
+      && sender
+        .send(TestEvent::Output(buffer[0..size].to_vec()))
+        .is_err()
     {
       break;
     }
+
+    // Always respond back if this was set. Ideally we would also check to
+    // ensure the pipe reader is empty before sending back this response.
+    if let Some(sender) = oneshot_sender {
+      let _ignore = sender.send(());
+    }
   });
 }