From ce00640b22bdfbc1cb90af8ef1efa610b295c44c Mon Sep 17 00:00:00 2001
From: "Jeong, YunWon" <69878+youknowone@users.noreply.github.com>
Date: Sun, 28 Dec 2025 09:08:03 +0900
Subject: [PATCH] fix input to check pty child (#6553)

* fix input to check pty child

* Auto-format: cargo fmt --all

---------

Co-authored-by: github-actions[bot] <github-actions[bot]@users.noreply.github.com>
---
 crates/vm/src/py_io.rs           |  9 ++++++---
 crates/vm/src/stdlib/builtins.rs | 28 ++++++++++++++++++++++++----
 2 files changed, 30 insertions(+), 7 deletions(-)

diff --git a/crates/vm/src/py_io.rs b/crates/vm/src/py_io.rs
index 6b82bbd47..a8063673a 100644
--- a/crates/vm/src/py_io.rs
+++ b/crates/vm/src/py_io.rs
@@ -70,11 +70,14 @@ pub fn file_readline(obj: &PyObject, size: Option<usize>, vm: &VirtualMachine) -
     };
     let ret = match_class!(match ret {
         s @ PyStr => {
-            let s_val = s.as_str();
-            if s_val.is_empty() {
+            // Use as_wtf8() to handle strings with surrogates (e.g., surrogateescape)
+            let s_wtf8 = s.as_wtf8();
+            if s_wtf8.is_empty() {
                 return Err(eof_err());
             }
-            if let Some(no_nl) = s_val.strip_suffix('\n') {
+            // '\n' is ASCII, so we can check bytes directly
+            if s_wtf8.as_bytes().last() == Some(&b'\n') {
+                let no_nl = &s_wtf8[..s_wtf8.len() - 1];
                 vm.ctx.new_str(no_nl).into()
             } else {
                 s.into()
diff --git a/crates/vm/src/stdlib/builtins.rs b/crates/vm/src/stdlib/builtins.rs
index 19f85af55..7cd91f8b4 100644
--- a/crates/vm/src/stdlib/builtins.rs
+++ b/crates/vm/src/stdlib/builtins.rs
@@ -7,8 +7,6 @@ pub use builtins::{ascii, print, reversed};
 
 #[pymodule]
 mod builtins {
-    use std::io::IsTerminal;
-
     use crate::{
         AsObject, PyObject, PyObjectRef, PyPayload, PyRef, PyResult, TryFromObject, VirtualMachine,
         builtins::{
@@ -464,6 +462,8 @@ mod builtins {
 
     #[pyfunction]
     fn input(prompt: OptionalArg<PyStrRef>, vm: &VirtualMachine) -> PyResult {
+        use std::io::IsTerminal;
+
         let stdin = sys::get_stdin(vm)?;
         let stdout = sys::get_stdout(vm)?;
         let stderr = sys::get_stderr(vm)?;
@@ -476,8 +476,13 @@ mod builtins {
                 .is_ok_and(|fd| fd == expected)
         };
 
-        // everything is normal, we can just rely on rustyline to use stdin/stdout
-        if fd_matches(&stdin, 0) && fd_matches(&stdout, 1) && std::io::stdin().is_terminal() {
+        // Check if we should use rustyline (interactive terminal, not PTY child)
+        let use_rustyline = fd_matches(&stdin, 0)
+            && fd_matches(&stdout, 1)
+            && std::io::stdin().is_terminal()
+            && !is_pty_child();
+
+        if use_rustyline {
             let prompt = prompt.as_ref().map_or("", |s| s.as_str());
             let mut readline = Readline::new(());
             match readline.readline(prompt) {
@@ -502,6 +507,21 @@ mod builtins {
         }
     }
 
+    /// Check if we're running in a PTY child process (e.g., after pty.fork()).
+    /// pty.fork() calls setsid(), making the child a session leader.
+    /// In this case, rustyline may hang because it uses raw mode.
+    #[cfg(unix)]
+    fn is_pty_child() -> bool {
+        use nix::unistd::{getpid, getsid};
+        // If this process is a session leader, we're likely in a PTY child
+        getsid(None) == Ok(getpid())
+    }
+
+    #[cfg(not(unix))]
+    fn is_pty_child() -> bool {
+        false
+    }
+
     #[pyfunction]
     fn isinstance(obj: PyObjectRef, typ: PyObjectRef, vm: &VirtualMachine) -> PyResult<bool> {
         obj.is_instance(&typ, vm)