Fix zed sometimes stopping by using setsid on interactive shells (#29070)

For some reason `SIGTTIN` sometimes gets sent to the process group,
causing it to stop when run from a terminal. This solves that issue by
putting the shell in a new session + progress group.

This allows removal of a workaround of using `exit 0;` to restore
handling of ctrl-c after exit. In testing this appears to no longer be
necessary.

Closes #27716

Release Notes:

- Fixed Zed sometimes becoming a stopped background process when run
from a terminal.

crates/project/src/environment.rs

@@ -273,23 +273,14 @@ async fn load_shell_environment(
     //
     // In certain shells we need to execute additional_command in order to
     // trigger the behavior of direnv, etc.
-    //
-    //
-    // The `exit 0` is the result of hours of debugging, trying to find out
-    // why running this command here, without `exit 0`, would mess
-    // up signal process for our process so that `ctrl-c` doesn't work
-    // anymore.
-    //
-    // We still don't know why `$SHELL -l -i -c '/usr/bin/env -0'`  would
-    // do that, but it does, and `exit 0` helps.
 
     let command = match shell_name {
         Some("fish") => format!(
-            "cd '{}'; emit fish_prompt; printf '%s' {MARKER}; /usr/bin/env; exit 0;",
+            "cd '{}'; emit fish_prompt; printf '%s' {MARKER}; /usr/bin/env;",
             dir.display()
         ),
         _ => format!(
-            "cd '{}'; printf '%s' {MARKER}; /usr/bin/env; exit 0;",
+            "cd '{}'; printf '%s' {MARKER}; /usr/bin/env;",
             dir.display()
         ),
     };
@@ -297,16 +288,21 @@ async fn load_shell_environment(
     // csh/tcsh only supports `-l` if it's the only flag. So this won't be a login shell.
     // Users must rely on vars from `~/.tcshrc` or `~/.cshrc` and not `.login` as a result.
     let args = match shell_name {
-        Some("tcsh") | Some("csh") => vec!["-i", "-c", &command],
-        _ => vec!["-l", "-i", "-c", &command],
+        Some("tcsh") | Some("csh") => vec!["-i".to_string(), "-c".to_string(), command],
+        _ => vec![
+            "-l".to_string(),
+            "-i".to_string(),
+            "-c".to_string(),
+            command,
+        ],
     };
 
-    let Some(output) = smol::process::Command::new(&shell)
-        .args(&args)
-        .output()
-        .await
-        .log_err()
-    else {
+    let Some(output) = smol::unblock(move || {
+        util::set_pre_exec_to_start_new_session(std::process::Command::new(&shell).args(&args))
+            .output()
+    })
+    .await
+    .log_err() else {
         return message(
             "Failed to spawn login shell to source login environment variables. See logs for details",
         );

crates/util/src/util.rs

@@ -321,21 +321,16 @@ pub fn load_login_shell_environment() -> Result<()> {
         .and_then(|home| home.into_string().ok())
         .map(|home| format!("cd '{home}';"));
 
-    // The `exit 0` is the result of hours of debugging, trying to find out
-    // why running this command here, without `exit 0`, would mess
-    // up signal process for our process so that `ctrl-c` doesn't work
-    // anymore.
-    // We still don't know why `$SHELL -l -i -c '/usr/bin/env -0'`  would
-    // do that, but it does, and `exit 0` helps.
     let shell_cmd = format!(
-        "{}printf '%s' {marker}; /usr/bin/env; exit 0;",
+        "{}printf '%s' {marker}; /usr/bin/env;",
         shell_cmd_prefix.as_deref().unwrap_or("")
     );
 
-    let output = std::process::Command::new(&shell)
-        .args(["-l", "-i", "-c", &shell_cmd])
-        .output()
-        .context("failed to spawn login shell to source login environment variables")?;
+    let output = set_pre_exec_to_start_new_session(
+        std::process::Command::new(&shell).args(["-l", "-i", "-c", &shell_cmd]),
+    )
+    .output()
+    .context("failed to spawn login shell to source login environment variables")?;
     if !output.status.success() {
         Err(anyhow!("login shell exited with error"))?;
     }
@@ -357,6 +352,26 @@ pub fn load_login_shell_environment() -> Result<()> {
     Ok(())
 }
 
+/// Configures the process to start a new session, to prevent interactive shells from taking control
+/// of the terminal.
+///
+/// For more details: https://registerspill.thorstenball.com/p/how-to-lose-control-of-your-shell
+pub fn set_pre_exec_to_start_new_session(
+    command: &mut std::process::Command,
+) -> &mut std::process::Command {
+    // safety: code in pre_exec should be signal safe.
+    // https://man7.org/linux/man-pages/man7/signal-safety.7.html
+    #[cfg(not(target_os = "windows"))]
+    unsafe {
+        use std::os::unix::process::CommandExt;
+        command.pre_exec(|| {
+            libc::setsid();
+            Ok(())
+        });
+    };
+    command
+}
+
 /// Parse the result of calling `usr/bin/env` with no arguments
 pub fn parse_env_output(env: &str, mut f: impl FnMut(String, String)) {
     let mut current_key: Option<String> = None;

crates/vim/Cargo.toml

@@ -28,7 +28,6 @@ futures.workspace = true
 gpui.workspace = true
 itertools.workspace = true
 language.workspace = true
-libc.workspace = true
 log.workspace = true
 multi_buffer.workspace = true
 nvim-rs = { git = "https://github.com/KillTheMule/nvim-rs", branch = "master", features = ["use_tokio"], optional = true }

crates/vim/src/command.rs

@@ -1519,18 +1519,7 @@ impl ShellExec {
             process.stdin(Stdio::null());
         };
 
-        // https://registerspill.thorstenball.com/p/how-to-lose-control-of-your-shell
-        //
-        // safety: code in pre_exec should be signal safe.
-        // https://man7.org/linux/man-pages/man7/signal-safety.7.html
-        #[cfg(not(target_os = "windows"))]
-        unsafe {
-            use std::os::unix::process::CommandExt;
-            process.pre_exec(|| {
-                libc::setsid();
-                Ok(())
-            });
-        };
+        util::set_pre_exec_to_start_new_session(&mut process);
         let is_read = self.is_read;
 
         let task = cx.spawn_in(window, async move |vim, cx| {