feat: tmux session attach mode (#901)

* feat: tmux session attach mode

* feat: example config update

* feat: move the comment down to be relevant

* feat: fix tmux not attaching from non-tmux env when using create_and_switch_client

* feat: make matching on tmux modes as described in suggestions

* feat: make tmux_session_attach_mode private

* feat: remove tmux mode cli option

* feat: wrap default value in quotation marks for tmux session mode

* feat: renames for tmux session management options

* feat: try to make tmux session mode description better

config.example.toml

@@ -47,6 +47,12 @@
 # Run inside tmux (default: false)
 # run_in_tmux = true
 
+# Changes the way topgrade interacts with
+# the tmux session, creating the session
+# and only attaching to it if not inside tmux
+# (default: "attach_if_not_in_session", allowed values: "attach_if_not_in_session", "attach_always")
+# tmux_session_mode = "attach_if_not_in_session"
+
 # Cleanup temporary or old files (default: false)
 # cleanup = true
 

src/config.rs

@@ -403,6 +403,8 @@ pub struct Misc {
 
     run_in_tmux: Option<bool>,
 
+    tmux_session_mode: Option<TmuxSessionMode>,
+
     cleanup: Option<bool>,
 
     notify_each_step: Option<bool>,
@@ -419,6 +421,19 @@ pub struct Misc {
     log_filters: Option<Vec<String>>,
 }
 
+#[derive(Clone, Copy, Debug, Deserialize, ValueEnum)]
+#[clap(rename_all = "snake_case")]
+#[serde(rename_all = "snake_case")]
+pub enum TmuxSessionMode {
+    AttachIfNotInSession,
+    AttachAlways,
+}
+
+pub struct TmuxConfig {
+    pub args: Vec<String>,
+    pub session_mode: TmuxSessionMode,
+}
+
 #[derive(Deserialize, Default, Debug, Merge)]
 #[serde(deny_unknown_fields)]
 pub struct Lensfun {
@@ -967,6 +982,15 @@ impl Config {
                 .unwrap_or(false)
     }
 
+    /// The preferred way to run the new tmux session.
+    fn tmux_session_mode(&self) -> TmuxSessionMode {
+        self.config_file
+            .misc
+            .as_ref()
+            .and_then(|misc| misc.tmux_session_mode)
+            .unwrap_or(TmuxSessionMode::AttachIfNotInSession)
+    }
+
     /// Tell whether we should perform cleanup steps.
     pub fn cleanup(&self) -> bool {
         self.opt.cleanup
@@ -1024,8 +1048,16 @@ impl Config {
         self.config_file.git.as_ref().and_then(|git| git.arguments.as_ref())
     }
 
+    pub fn tmux_config(&self) -> Result<TmuxConfig> {
+        let args = self.tmux_arguments()?;
+        Ok(TmuxConfig {
+            args,
+            session_mode: self.tmux_session_mode(),
+        })
+    }
+
     /// Extra Tmux arguments
-    pub fn tmux_arguments(&self) -> Result<Vec<String>> {
+    fn tmux_arguments(&self) -> Result<Vec<String>> {
         let args = &self
             .config_file
             .misc

src/main.rs

@@ -118,7 +118,7 @@ fn run() -> Result<()> {
     if config.run_in_tmux() && env::var("TOPGRADE_INSIDE_TMUX").is_err() {
         #[cfg(unix)]
         {
-            tmux::run_in_tmux(config.tmux_arguments()?)?;
+            tmux::run_in_tmux(config.tmux_config()?)?;
             return Ok(());
         }
     }

src/steps/tmux.rs

@@ -7,6 +7,8 @@ use color_eyre::eyre::Context;
 use color_eyre::eyre::Result;
 
 use crate::command::CommandExt;
+use crate::config::TmuxConfig;
+use crate::config::TmuxSessionMode;
 use crate::terminal::print_separator;
 use crate::HOME_DIR;
 use crate::{
@@ -131,7 +133,7 @@ impl Tmux {
     }
 }
 
-pub fn run_in_tmux(args: Vec<String>) -> Result<()> {
+pub fn run_in_tmux(config: TmuxConfig) -> Result<()> {
     let command = {
         let mut command = vec![
             String::from("env"),
@@ -144,25 +146,39 @@ pub fn run_in_tmux(args: Vec<String>) -> Result<()> {
         shell_words::join(command)
     };
 
-    let tmux = Tmux::new(args);
+    let tmux = Tmux::new(config.args);
 
     // Find an unused session and run `topgrade` in it with the current command's arguments.
     let session_name = "topgrade";
     let window_name = "topgrade";
     let session = tmux.new_unique_session(session_name, window_name, &command)?;
 
-    // Only attach to the newly-created session if we're not currently in a tmux session.
-    if env::var("TMUX").is_err() {
-        let err = tmux.build().args(["attach-session", "-t", &session]).exec();
-        Err(eyre!("{err}")).context("Failed to `execvp(3)` tmux")
-    } else {
-        println!("Topgrade launched in a new tmux session");
-        Ok(())
-    }
+    let is_inside_tmux = env::var("TMUX").is_ok();
+    let err = match config.session_mode {
+        TmuxSessionMode::AttachIfNotInSession => {
+            if is_inside_tmux {
+                // Only attach to the newly-created session if we're not currently in a tmux session.
+                println!("Topgrade launched in a new tmux session");
+                return Ok(());
+            } else {
+                tmux.build().args(["attach-client", "-t", &session]).exec()
+            }
+        }
+
+        TmuxSessionMode::AttachAlways => {
+            if is_inside_tmux {
+                tmux.build().args(["switch-client", "-t", &session]).exec()
+            } else {
+                tmux.build().args(["attach-client", "-t", &session]).exec()
+            }
+        }
+    };
+
+    Err(eyre!("{err}")).context("Failed to `execvp(3)` tmux")
 }
 
 pub fn run_command(ctx: &ExecutionContext, window_name: &str, command: &str) -> Result<()> {
-    let tmux = Tmux::new(ctx.config().tmux_arguments()?);
+    let tmux = Tmux::new(ctx.config().tmux_config()?.args);
 
     match ctx.get_tmux_session() {
         Some(session_name) => {