Add a method to query a unique session id (#759)

* Add a method to query a unique session id

* Update crates/ark/src/reticulate.rs

Co-authored-by: Lionel Henry <[email protected]>

* Use LazyLock

---------

Co-authored-by: Lionel Henry <[email protected]>

Author: dfalbel

crates/ark/src/modules/positron/reticulate.R

@@ -127,3 +127,8 @@
         }
     )
 }
+
+#' @export
+.ps.rpc.reticulate_id <- function() {
+    .ps.Call("ps_reticulate_id")
+}

crates/ark/src/reticulate.rs

@@ -22,6 +22,11 @@ use crate::interface::RMain;
 static RETICULATE_OUTGOING_TX: LazyLock<Mutex<Option<Sender<CommMsg>>>> =
     LazyLock::new(|| Mutex::new(None));
 
+// Each ark session has a unique session id which is used by the Positron frontend
+// to associate a client id with a session.
+static RETICULATE_ID: LazyLock<String> =
+    LazyLock::new(|| format!("reticulate-{}", Uuid::new_v4().to_string()));
+
 #[derive(Clone)]
 pub struct ReticulateService {
     comm: CommSocket,
@@ -53,7 +58,8 @@ impl ReticulateService {
         let event = CommManagerEvent::Opened(
             service.comm.clone(),
             json!({
-                "input": input
+                "input": input,
+                "reticulate_id": (*RETICULATE_ID).clone(),
             }),
         );
         service
@@ -137,3 +143,8 @@ pub unsafe extern "C-unwind" fn ps_reticulate_open(input: SEXP) -> Result<SEXP,
 
     Ok(R_NilValue)
 }
+
+#[harp::register]
+pub unsafe extern "C-unwind" fn ps_reticulate_id() -> Result<SEXP, anyhow::Error> {
+    Ok(RObject::from((*RETICULATE_ID).clone()).sexp)
+}