Prevent a zellij session from attaching to itself. (#911)

* fix #905
Prevent a zellij session from attaching to itself.

* Add check while attaching using index as well

src/commands.rs

@@ -16,6 +16,7 @@ use zellij_utils::input::options::Options;
 use zellij_utils::nix;
 use zellij_utils::{
     cli::{CliArgs, Command, SessionCommand, Sessions},
+    envs,
     setup::{get_default_data_dir, Setup},
 };
 
@@ -186,6 +187,13 @@ pub(crate) fn start_client(opts: CliArgs) {
             attach_with_session_name(session_name, config_options.clone(), create)
         };
 
+        if let Ok(val) = std::env::var(envs::SESSION_NAME_ENV_KEY) {
+            if val == *client.get_session_name() {
+                eprintln!("You are trying to attach to the current session(\"{}\"). Zellij does not support nesting a session in itself", val);
+                process::exit(1);
+            }
+        }
+
         let attach_layout = match client {
             ClientInfo::Attach(_, _) => None,
             ClientInfo::New(_) => layout,

zellij-client/src/lib.rs

@@ -91,6 +91,15 @@ pub enum ClientInfo {
     New(String),
 }
 
+impl ClientInfo {
+    pub fn get_session_name(&self) -> &str {
+        match self {
+            Self::Attach(ref name, _) => name,
+            Self::New(ref name) => name,
+        }
+    }
+}
+
 #[derive(Debug, Clone)]
 pub(crate) enum InputInstruction {
     KeyEvent(termion::event::Event, Vec<u8>),