Fix double panic lockup in clients panic handler (#1433)

* Fix possible lockup in the clients panic handler

When the pty the client was running in disappears, reading from stdin
causes a panic, which triggers the custom panic handler. This handler
attempts to print a backtrace to the terminal and tries to unset the raw
mode for that. Since the pty has already disappeared, the tcsetattr call
fails and causes a second panic, which locks everything up.

This commit fixes this by returning an Result from the unset_raw_mode
function, allowing the calling panic handler to handle any error
gracefully.

* Log any client panics to file

Since we are now aware of the fact that panics may happen / are handled
after the pty has disappeared, logging them to file seems useful: there
is no other other place to show them to the user.

* fix tests and improve function return type

3 files changed, 15 insertions, 14 deletions

diff --git a/zellij-client/src/lib.rs b/zellij-client/src/lib.rs
index bd5b04f54..5ddaa5fee 100644
--- a/zellij-client/src/lib.rs
+++ b/zellij-client/src/lib.rs
@@ -5,6 +5,7 @@ mod input_handler;
 mod stdin_ansi_parser;
 mod stdin_handler;
 
+use log::error;
 use log::info;
 use std::env::current_exe;
 use std::io::{self, Write};
@@ -124,7 +125,7 @@ pub fn start_client(
     let clear_client_terminal_attributes = "\u{1b}[?1l\u{1b}=\u{1b}[r\u{1b}12l\u{1b}[?1000l\u{1b}[?1002l\u{1b}[?1003l\u{1b}[?1005l\u{1b}[?1006l\u{1b}[?12l";
     let take_snapshot = "\u{1b}[?1049h";
     let bracketed_paste = "\u{1b}[?2004h";
-    os_input.unset_raw_mode(0);
+    os_input.unset_raw_mode(0).unwrap();
 
     let _ = os_input
         .get_stdout_writer()
@@ -201,8 +202,10 @@ pub fn start_client(
         let send_client_instructions = send_client_instructions.clone();
         let os_input = os_input.clone();
         Box::new(move |info| {
-            os_input.unset_raw_mode(0);
-            handle_panic(info, &send_client_instructions);
+            error!("Panic occured in client:\n{:?}", info);
+            if let Ok(()) = os_input.unset_raw_mode(0) {
+                handle_panic(info, &send_client_instructions);
+            }
         })
     });
 
@@ -293,7 +296,7 @@ pub fn start_client(
         .unwrap();
 
     let handle_error = |backtrace: String| {
-        os_input.unset_raw_mode(0);
+        os_input.unset_raw_mode(0).unwrap();
         let goto_start_of_last_line = format!("\u{1b}[{};{}H", full_screen_ws.rows, 1);
         let restore_snapshot = "\u{1b}[?1049l";
         os_input.disable_mouse();
@@ -364,7 +367,7 @@ pub fn start_client(
 
     os_input.disable_mouse();
     info!("{}", exit_msg);
-    os_input.unset_raw_mode(0);
+    os_input.unset_raw_mode(0).unwrap();
     let mut stdout = os_input.get_stdout_writer();
     let _ = stdout.write(goodbye_message.as_bytes()).unwrap();
     stdout.flush().unwrap();
diff --git a/zellij-client/src/os_input_output.rs b/zellij-client/src/os_input_output.rs
index b93b6121d..f3e916c48 100644
--- a/zellij-client/src/os_input_output.rs
+++ b/zellij-client/src/os_input_output.rs
@@ -32,11 +32,8 @@ fn into_raw_mode(pid: RawFd) {
     };
 }
 
-fn unset_raw_mode(pid: RawFd, orig_termios: termios::Termios) {
-    match termios::tcsetattr(pid, termios::SetArg::TCSANOW, &orig_termios) {
-        Ok(_) => {}
-        Err(e) => panic!("error {:?}", e),
-    };
+fn unset_raw_mode(pid: RawFd, orig_termios: termios::Termios) -> Result<(), nix::Error> {
+    termios::tcsetattr(pid, termios::SetArg::TCSANOW, &orig_termios)
 }
 
 pub(crate) fn get_terminal_size_using_fd(fd: RawFd) -> Size {
@@ -81,7 +78,7 @@ pub trait ClientOsApi: Send + Sync {
     fn set_raw_mode(&mut self, fd: RawFd);
     /// Set the terminal associated to file descriptor `fd` to
     /// [cooked mode](https://en.wikipedia.org/wiki/Terminal_mode).
-    fn unset_raw_mode(&self, fd: RawFd);
+    fn unset_raw_mode(&self, fd: RawFd) -> Result<(), nix::Error>;
     /// Returns the writer that allows writing to standard output.
     fn get_stdout_writer(&self) -> Box<dyn io::Write>;
     fn get_stdin_reader(&self) -> Box<dyn io::Read>;
@@ -111,9 +108,9 @@ impl ClientOsApi for ClientOsInputOutput {
     fn set_raw_mode(&mut self, fd: RawFd) {
         into_raw_mode(fd);
     }
-    fn unset_raw_mode(&self, fd: RawFd) {
+    fn unset_raw_mode(&self, fd: RawFd) -> Result<(), nix::Error> {
         let orig_termios = self.orig_termios.lock().unwrap();
-        unset_raw_mode(fd, orig_termios.clone());
+        unset_raw_mode(fd, orig_termios.clone())
     }
     fn box_clone(&self) -> Box<dyn ClientOsApi> {
         Box::new((*self).clone())
diff --git a/zellij-client/src/unit/input_handler_tests.rs b/zellij-client/src/unit/input_handler_tests.rs
index 4b830656f..ba5ac11c2 100644
--- a/zellij-client/src/unit/input_handler_tests.rs
+++ b/zellij-client/src/unit/input_handler_tests.rs
@@ -2,6 +2,7 @@ use super::input_loop;
 use zellij_utils::input::actions::{Action, Direction};
 use zellij_utils::input::config::Config;
 use zellij_utils::input::options::Options;
+use zellij_utils::nix;
 use zellij_utils::pane_size::{Size, SizeInPixels};
 use zellij_utils::termwiz::input::{InputEvent, KeyCode, KeyEvent, Modifiers};
 use zellij_utils::zellij_tile::data::Palette;
@@ -125,7 +126,7 @@ impl ClientOsApi for FakeClientOsApi {
     fn set_raw_mode(&mut self, _fd: RawFd) {
         unimplemented!()
     }
-    fn unset_raw_mode(&self, _fd: RawFd) {
+    fn unset_raw_mode(&self, _fd: RawFd) -> Result<(), nix::Error> {
         unimplemented!()
     }
     fn get_stdout_writer(&self) -> Box<dyn io::Write> {