fix(ext/node): windows cancel stdin read in line mode (#23969)

This patch fixes stdin read hanging on user input when switching tty
mode on Windows

Fixes #21111

On Windows, when switching from line to raw mode:
- Cancel ongoing console read by writing a return keypress to its input
buffer. This blocks the main thread until any ongoing read has been
cancelled to prevent interference with the screen state.
- On the read thread, restore the cursor position to where it was before
writing the enter, undoing its effect on the screen state.
- Restart reading and notify the main thread.

Cargo.lock

@@ -1555,6 +1555,7 @@ dependencies = [
  "log",
  "once_cell",
  "os_pipe",
+ "parking_lot 0.12.1",
  "rand",
  "tokio",
  "winapi",

ext/io/Cargo.toml

@@ -28,3 +28,4 @@ os_pipe.workspace = true
 [target.'cfg(windows)'.dependencies]
 winapi = { workspace = true, features = ["winbase", "processenv", "errhandlingapi"] }
 rand.workspace = true
+parking_lot.workspace = true

ext/io/lib.rs

@@ -48,6 +48,13 @@ use winapi::um::processenv::GetStdHandle;
 #[cfg(windows)]
 use winapi::um::winbase;
 
+#[cfg(windows)]
+use parking_lot::Condvar;
+#[cfg(windows)]
+use parking_lot::Mutex;
+#[cfg(windows)]
+use std::sync::Arc;
+
 pub mod fs;
 mod pipe;
 #[cfg(windows)]
@@ -106,12 +113,21 @@ deno_core::extension!(deno_io,
   },
   state = |state, options| {
     if let Some(stdio) = options.stdio {
+      #[cfg(windows)]
+      let stdin_state = {
+        let st = Arc::new(Mutex::new(WinTtyState::default()));
+        state.put(st.clone());
+        st
+      };
+      #[cfg(unix)]
+      let stdin_state = ();
+
       let t = &mut state.resource_table;
 
       let rid = t.add(fs::FileResource::new(
         Rc::new(match stdio.stdin.pipe {
           StdioPipeInner::Inherit => StdFileResourceInner::new(
-            StdFileResourceKind::Stdin,
+            StdFileResourceKind::Stdin(stdin_state),
             STDIN_HANDLE.try_clone().unwrap(),
           ),
           StdioPipeInner::File(pipe) => StdFileResourceInner::file(pipe),
@@ -317,14 +333,27 @@ impl Resource for ChildStderrResource {
   }
 }
 
-#[derive(Clone, Copy)]
+#[cfg(windows)]
+#[derive(Default)]
+pub struct WinTtyState {
+  pub cancelled: bool,
+  pub reading: bool,
+  pub screen_buffer_info:
+    Option<winapi::um::wincon::CONSOLE_SCREEN_BUFFER_INFO>,
+  pub cvar: Arc<Condvar>,
+}
+
+#[derive(Clone)]
 enum StdFileResourceKind {
   File,
   // For stdout and stderr, we sometimes instead use std::io::stdout() directly,
   // because we get some Windows specific functionality for free by using Rust
   // std's wrappers. So we take a bit of a complexity hit in order to not
   // have to duplicate the functionality in Rust's std/src/sys/windows/stdio.rs
-  Stdin,
+  #[cfg(windows)]
+  Stdin(Arc<Mutex<WinTtyState>>),
+  #[cfg(not(windows))]
+  Stdin(()),
   Stdout,
   Stderr,
 }
@@ -422,6 +451,84 @@ impl StdFileResourceInner {
       spawn_blocking(action).await.unwrap()
     }
   }
+
+  #[cfg(windows)]
+  async fn handle_stdin_read(
+    &self,
+    state: Arc<Mutex<WinTtyState>>,
+    mut buf: BufMutView,
+  ) -> FsResult<(usize, BufMutView)> {
+    loop {
+      let state = state.clone();
+
+      let fut = self.with_inner_blocking_task(move |file| {
+        /* Start reading, and set the reading flag to true */
+        state.lock().reading = true;
+        let nread = match file.read(&mut buf) {
+          Ok(nread) => nread,
+          Err(e) => return Err((e.into(), buf)),
+        };
+
+        let mut state = state.lock();
+        state.reading = false;
+
+        /* If we canceled the read by sending a VK_RETURN event, restore
+        the screen state to undo the visual effect of the VK_RETURN event */
+        if state.cancelled {
+          if let Some(screen_buffer_info) = state.screen_buffer_info {
+            // SAFETY: WinAPI calls to open conout$ and restore visual state.
+            unsafe {
+              let handle = winapi::um::fileapi::CreateFileW(
+                "conout$"
+                  .encode_utf16()
+                  .chain(Some(0))
+                  .collect::<Vec<_>>()
+                  .as_ptr(),
+                winapi::um::winnt::GENERIC_READ
+                  | winapi::um::winnt::GENERIC_WRITE,
+                winapi::um::winnt::FILE_SHARE_READ
+                  | winapi::um::winnt::FILE_SHARE_WRITE,
+                std::ptr::null_mut(),
+                winapi::um::fileapi::OPEN_EXISTING,
+                0,
+                std::ptr::null_mut(),
+              );
+
+              let mut pos = screen_buffer_info.dwCursorPosition;
+              /* If the cursor was at the bottom line of the screen buffer, the
+              VK_RETURN would have caused the buffer contents to scroll up by
+              one line. The right position to reset the cursor to is therefore one
+              line higher */
+              if pos.Y == screen_buffer_info.dwSize.Y - 1 {
+                pos.Y -= 1;
+              }
+
+              winapi::um::wincon::SetConsoleCursorPosition(handle, pos);
+              winapi::um::handleapi::CloseHandle(handle);
+            }
+          }
+
+          /* Reset the cancelled flag */
+          state.cancelled = false;
+
+          /* Unblock the main thread */
+          state.cvar.notify_one();
+
+          return Err((FsError::FileBusy, buf));
+        }
+
+        Ok((nread, buf))
+      });
+
+      match fut.await {
+        Err((FsError::FileBusy, b)) => {
+          buf = b;
+          continue;
+        }
+        other => return other.map_err(|(e, _)| e),
+      }
+    }
+  }
 }
 
 #[async_trait::async_trait(?Send)]
@@ -435,7 +542,7 @@ impl crate::fs::File for StdFileResourceInner {
     // std/src/sys/windows/stdio.rs in Rust's source code).
     match self.kind {
       StdFileResourceKind::File => self.with_sync(|file| Ok(file.write(buf)?)),
-      StdFileResourceKind::Stdin => {
+      StdFileResourceKind::Stdin(_) => {
         Err(Into::<std::io::Error>::into(ErrorKind::Unsupported).into())
       }
       StdFileResourceKind::Stdout => {
@@ -457,7 +564,7 @@ impl crate::fs::File for StdFileResourceInner {
 
   fn read_sync(self: Rc<Self>, buf: &mut [u8]) -> FsResult<usize> {
     match self.kind {
-      StdFileResourceKind::File | StdFileResourceKind::Stdin => {
+      StdFileResourceKind::File | StdFileResourceKind::Stdin(_) => {
         self.with_sync(|file| Ok(file.read(buf)?))
       }
       StdFileResourceKind::Stdout | StdFileResourceKind::Stderr => {
@@ -471,7 +578,7 @@ impl crate::fs::File for StdFileResourceInner {
       StdFileResourceKind::File => {
         self.with_sync(|file| Ok(file.write_all(buf)?))
       }
-      StdFileResourceKind::Stdin => {
+      StdFileResourceKind::Stdin(_) => {
         Err(Into::<std::io::Error>::into(ErrorKind::Unsupported).into())
       }
       StdFileResourceKind::Stdout => {
@@ -497,7 +604,7 @@ impl crate::fs::File for StdFileResourceInner {
           .with_inner_blocking_task(move |file| Ok(file.write_all(&buf)?))
           .await
       }
-      StdFileResourceKind::Stdin => {
+      StdFileResourceKind::Stdin(_) => {
         Err(Into::<std::io::Error>::into(ErrorKind::Unsupported).into())
       }
       StdFileResourceKind::Stdout => {
@@ -538,7 +645,7 @@ impl crate::fs::File for StdFileResourceInner {
           })
           .await
       }
-      StdFileResourceKind::Stdin => {
+      StdFileResourceKind::Stdin(_) => {
         Err(Into::<std::io::Error>::into(ErrorKind::Unsupported).into())
       }
       StdFileResourceKind::Stdout => {
@@ -568,7 +675,7 @@ impl crate::fs::File for StdFileResourceInner {
 
   fn read_all_sync(self: Rc<Self>) -> FsResult<Vec<u8>> {
     match self.kind {
-      StdFileResourceKind::File | StdFileResourceKind::Stdin => {
+      StdFileResourceKind::File | StdFileResourceKind::Stdin(_) => {
         let mut buf = Vec::new();
         self.with_sync(|file| Ok(file.read_to_end(&mut buf)?))?;
         Ok(buf)
@@ -580,7 +687,7 @@ impl crate::fs::File for StdFileResourceInner {
   }
   async fn read_all_async(self: Rc<Self>) -> FsResult<Vec<u8>> {
     match self.kind {
-      StdFileResourceKind::File | StdFileResourceKind::Stdin => {
+      StdFileResourceKind::File | StdFileResourceKind::Stdin(_) => {
         self
           .with_inner_blocking_task(|file| {
             let mut buf = Vec::new();
@@ -736,6 +843,13 @@ impl crate::fs::File for StdFileResourceInner {
     self: Rc<Self>,
     mut buf: BufMutView,
   ) -> FsResult<(usize, BufMutView)> {
+    match &self.kind {
+      /* On Windows, we need to handle special read cancellation logic for stdin */
+      #[cfg(windows)]
+      StdFileResourceKind::Stdin(state) => {
+        self.handle_stdin_read(state.clone(), buf).await
+      }
+      _ => {
         self
           .with_inner_blocking_task(|file| {
             let nread = file.read(&mut buf)?;
@@ -743,12 +857,14 @@ impl crate::fs::File for StdFileResourceInner {
           })
           .await
       }
+    }
+  }
 
   fn try_clone_inner(self: Rc<Self>) -> FsResult<Rc<dyn fs::File>> {
     let inner: &Option<_> = &self.cell.borrow();
     match inner {
       Some(inner) => Ok(Rc::new(StdFileResourceInner {
-        kind: self.kind,
+        kind: self.kind.clone(),
         cell: RefCell::new(Some(inner.try_clone()?)),
         cell_async_task_queue: Default::default(),
         handle: self.handle,

runtime/ops/tty.rs

@@ -13,6 +13,13 @@ use rustyline::KeyCode;
 use rustyline::KeyEvent;
 use rustyline::Modifiers;
 
+#[cfg(windows)]
+use deno_core::parking_lot::Mutex;
+#[cfg(windows)]
+use deno_io::WinTtyState;
+#[cfg(windows)]
+use std::sync::Arc;
+
 #[cfg(unix)]
 use deno_core::ResourceId;
 #[cfg(unix)]
@@ -94,6 +101,7 @@ fn op_set_raw(
   #[cfg(windows)]
   {
     use winapi::shared::minwindef::FALSE;
+
     use winapi::um::consoleapi;
 
     let handle = handle_or_fd;
@@ -116,6 +124,79 @@ fn op_set_raw(
       mode_raw_input_off(original_mode)
     };
 
+    let stdin_state = state.borrow::<Arc<Mutex<WinTtyState>>>();
+    let mut stdin_state = stdin_state.lock();
+
+    if stdin_state.reading {
+      let cvar = stdin_state.cvar.clone();
+
+      /* Trick to unblock an ongoing line-buffered read operation if not already pending.
+      See https://github.com/libuv/libuv/pull/866 for prior art */
+      if original_mode & COOKED_MODE != 0 && !stdin_state.cancelled {
+        // SAFETY: Write enter key event to force the console wait to return.
+        let record = unsafe {
+          let mut record: wincon::INPUT_RECORD = std::mem::zeroed();
+          record.EventType = wincon::KEY_EVENT;
+          record.Event.KeyEvent_mut().wVirtualKeyCode =
+            winapi::um::winuser::VK_RETURN as u16;
+          record.Event.KeyEvent_mut().bKeyDown = 1;
+          record.Event.KeyEvent_mut().wRepeatCount = 1;
+          *record.Event.KeyEvent_mut().uChar.UnicodeChar_mut() = '\r' as u16;
+          record.Event.KeyEvent_mut().dwControlKeyState = 0;
+          record.Event.KeyEvent_mut().wVirtualScanCode =
+            winapi::um::winuser::MapVirtualKeyW(
+              winapi::um::winuser::VK_RETURN as u32,
+              winapi::um::winuser::MAPVK_VK_TO_VSC,
+            ) as u16;
+          record
+        };
+        stdin_state.cancelled = true;
+
+        // SAFETY: winapi call to open conout$ and save screen state.
+        let active_screen_buffer = unsafe {
+          /* Save screen state before sending the VK_RETURN event */
+          let handle = winapi::um::fileapi::CreateFileW(
+            "conout$"
+              .encode_utf16()
+              .chain(Some(0))
+              .collect::<Vec<_>>()
+              .as_ptr(),
+            winapi::um::winnt::GENERIC_READ | winapi::um::winnt::GENERIC_WRITE,
+            winapi::um::winnt::FILE_SHARE_READ
+              | winapi::um::winnt::FILE_SHARE_WRITE,
+            std::ptr::null_mut(),
+            winapi::um::fileapi::OPEN_EXISTING,
+            0,
+            std::ptr::null_mut(),
+          );
+
+          let mut active_screen_buffer = std::mem::zeroed();
+          winapi::um::wincon::GetConsoleScreenBufferInfo(
+            handle,
+            &mut active_screen_buffer,
+          );
+          winapi::um::handleapi::CloseHandle(handle);
+          active_screen_buffer
+        };
+        stdin_state.screen_buffer_info = Some(active_screen_buffer);
+
+        // SAFETY: winapi call to write the VK_RETURN event.
+        if unsafe {
+          winapi::um::wincon::WriteConsoleInputW(handle, &record, 1, &mut 0)
+        } == FALSE
+        {
+          return Err(Error::last_os_error().into());
+        }
+
+        /* Wait for read thread to acknowledge the cancellation to ensure that nothing
+        interferes with the screen state.
+        NOTE: `wait_while` automatically unlocks stdin_state */
+        cvar.wait_while(&mut stdin_state, |state: &mut WinTtyState| {
+          state.cancelled
+        });
+      }
+    }
+
     // SAFETY: winapi call
     if unsafe { consoleapi::SetConsoleMode(handle, new_mode) } == FALSE {
       return Err(Error::last_os_error().into());

tests/integration/run_tests.rs

@@ -3141,6 +3141,20 @@ itest!(byte_order_mark {
   output: "run/byte_order_mark.out",
 });
 
+#[test]
+#[cfg(windows)]
+fn process_stdin_read_unblock() {
+  TestContext::default()
+    .new_command()
+    .args_vec(["run", "run/process_stdin_unblock.mjs"])
+    .with_pty(|mut console| {
+      console.write_raw("b");
+      console.human_delay();
+      console.write_line_raw("s");
+      console.expect_all(&["1", "1"]);
+    });
+}
+
 #[test]
 fn issue9750() {
   TestContext::default()

tests/testdata/run/process_stdin_unblock.mjs

@@ -0,0 +1,21 @@
+import process from "node:process";
+
+function prompt() {
+  process.stdin.setRawMode(true);
+
+  const { promise, resolve } = Promise.withResolvers();
+
+  const onData = (buf) => {
+    process.stdin.setRawMode(false);
+    process.stdin.removeListener("data", onData);
+    console.log(buf.length);
+    resolve();
+  };
+
+  process.stdin.on("data", onData);
+  return promise;
+}
+
+await prompt();
+await prompt();
+Deno.exit(0);