Reticulate support (#506)

* Add rpc method to query reticulate interpreters

* Add events for reticulate

* Make sure thre's a single reticulate thread

* Remove unncessary reticulate focus command

* Cleanup

* Remove unnecessary id

* Send code to R main thread

* Input code

* Allow optional

* Correctly acquire input

* Create a method to start kernels

* Add install reticulate method

* Add more method to make checks on R environment

* Apply suggestions from code review

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

* Improvements to style and simplifications

* Add some comments + install packages rpc method

---------

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

Author: dfalbel

crates/ark/src/lib.rs

@@ -26,6 +26,7 @@ pub mod modules_utils;
 pub mod plots;
 pub mod r_task;
 pub mod request;
+pub mod reticulate;
 pub mod shell;
 pub mod signals;
 pub mod srcref;

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

@@ -21,6 +21,17 @@
 #' @export
 .ps.rpc.is_installed <- .ps.is_installed
 
+#' @export
+.ps.rpc.install_packages <- function(packages) {
+    for (pkg in packages) {
+        if (.ps.rpc.isPackageAttached(pkg)) {
+            stop("Should not install a package if it's already attached.")
+        }
+    }
+    utils::install.packages(packages)
+    TRUE
+}
+
 #' @export
 .ps.rpc.isPackageAttached <- function(pkg) {
     if (!is_string(pkg)) {

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

@@ -0,0 +1,92 @@
+#' @export
+.ps.reticulate_open <- function(input="") {
+    .ps.Call("ps_reticulate_open", input)
+}
+
+#' Called by the front-end right before starting the reticulate session.
+#'
+#' At this point it should be fine to load Python if it's not loaded, and
+#' check if it can be started and if necessary packages are installed.
+#' @export
+.ps.rpc.reticulate_check_prerequisites <- function() {
+
+    # This should return a list with the following fields:
+    # python: NULL or string
+    # venv: NULL or string
+    # ipykernel: NULL or string
+    # error: NULL or string
+
+    config <- tryCatch({
+        reticulate::py_discover_config()
+    }, error = function(err) {
+        err
+    })
+
+    if (inherits(config, "error")) {
+        # py_discover_config() can fail if the user forced a Python session
+        # via RETICULATE_PYTHON, but this version doesn't exist.
+        return(list(error = conditionMessage(config)))
+    }
+
+    if (is.null(config) || is.null(config$python)) {
+        # The front-end will offer to install Python.
+        return(list(python = NULL, error = NULL))
+    }
+
+    python <- config$python
+    venv <- config$virtualenv
+
+    # Check that python can be loaded, if it can't we will throw
+    # an error, which is unrecoverable.
+    config <- tryCatch({
+        reticulate::py_config()
+    }, error = function(err) {
+        err
+    })
+
+    if (inherits(config, "error")) {
+        return(list(python = python, venv = venv, error = conditionMessage(config)))
+    }
+
+    # Now check ipykernel
+    ipykernel <- tryCatch({
+        reticulate::py_module_available("ipykernel")
+    }, error = function(err) {
+        err
+    })
+
+    if (inherits(ipykernel, "error")) {
+        return(list(python = python, venv = venv, error = conditionMessage(ipykernel)))
+    }
+
+    list(
+        python = config$python,
+        venv = venv,
+        ipykernel = ipykernel,
+        error = NULL
+    )
+}
+
+#' @export
+.ps.rpc.reticulate_start_kernel <- function(kernelPath, connectionFile, logFile, logLevel) {
+    # Starts an IPykernel in a separate thread with information provided by
+    # the caller.
+    # It it's essentially executing the kernel startup script:
+    # https://github.com/posit-dev/positron/blob/main/extensions/positron-python/python_files/positron/positron_language_server.py
+    # and passing the communication files that Positron Jupyter's Adapter sets up.
+    tryCatch({
+        reticulate:::py_run_file_on_thread(
+            file = kernelPath,
+            args = c(
+                "-f", connectionFile,
+                "--logfile", logFile,
+                "--loglevel", logLevel,
+                "--session-mode", "console"
+            )
+        )
+        # Empty string means that no error happened.
+        ""
+    }, error = function(err) {
+        conditionMessage(err)
+    })
+}

crates/ark/src/reticulate.rs

@@ -0,0 +1,117 @@
+use std::ops::Deref;
+use std::sync::LazyLock;
+use std::sync::Mutex;
+
+use amalthea::comm::comm_channel::CommMsg;
+use amalthea::comm::event::CommManagerEvent;
+use amalthea::socket::comm::CommInitiator;
+use amalthea::socket::comm::CommSocket;
+use crossbeam::channel::Sender;
+use harp::RObject;
+use libr::R_NilValue;
+use libr::SEXP;
+use serde_json::json;
+use stdext::result::ResultOrLog;
+use stdext::spawn;
+use stdext::unwrap;
+use uuid::Uuid;
+
+use crate::interface::RMain;
+
+static RETICULATE_COMM_ID: LazyLock<Mutex<Option<String>>> = LazyLock::new(|| Mutex::new(None));
+
+pub struct ReticulateService {
+    comm: CommSocket,
+    comm_manager_tx: Sender<CommManagerEvent>,
+}
+
+impl ReticulateService {
+    fn start(comm_id: String, comm_manager_tx: Sender<CommManagerEvent>) -> anyhow::Result<String> {
+        let comm = CommSocket::new(
+            CommInitiator::BackEnd,
+            comm_id.clone(),
+            String::from("positron.reticulate"),
+        );
+
+        let service = Self {
+            comm,
+            comm_manager_tx,
+        };
+
+        let event = CommManagerEvent::Opened(service.comm.clone(), serde_json::Value::Null);
+        service
+            .comm_manager_tx
+            .send(event)
+            .or_log_error("Reticulate: Could not open comm.");
+
+        spawn!(format!("ark-reticulate-{}", comm_id), move || {
+            service
+                .handle_messages()
+                .or_log_error("Reticulate: Error handling messages");
+        });
+
+        Ok(comm_id)
+    }
+
+    fn handle_messages(&self) -> Result<(), anyhow::Error> {
+        loop {
+            let msg = unwrap!(self.comm.incoming_rx.recv(), Err(err) => {
+                log::error!("Reticulate: Error while receiving message from frontend: {err:?}");
+                break;
+            });
+
+            if let CommMsg::Close = msg {
+                break;
+            }
+        }
+
+        // before finalizing the thread we make sure to send a close message to the front end
+        self.comm
+            .outgoing_tx
+            .send(CommMsg::Close)
+            .or_log_error("Reticulate: Could not send close message to the front-end");
+
+        // Reset the global comm_id before closing
+        let mut comm_id_guard = RETICULATE_COMM_ID.lock().unwrap();
+        log::info!("Reticulate Thread closing {:?}", (*comm_id_guard).clone());
+        *comm_id_guard = None;
+
+        Ok(())
+    }
+}
+
+// Creates a client instance reticulate can use to communicate with the front-end.
+// We should aim at having at most **1** client per R session.
+// Further actions that reticulate can ask the front-end can be requested through
+// the comm_id that is returned by this function.
+#[harp::register]
+pub unsafe extern "C" fn ps_reticulate_open(input: SEXP) -> Result<SEXP, anyhow::Error> {
+    let main = RMain::get();
+
+    let input: RObject = input.try_into()?;
+    let input_code: Option<String> = input.try_into()?;
+
+    let mut comm_id_guard = RETICULATE_COMM_ID.lock().unwrap();
+
+    // If there's an id already registered, we just need to send the focus event
+    if let Some(id) = comm_id_guard.deref() {
+        // There's a comm_id registered, we just send the focus event
+        main.get_comm_manager_tx().send(CommManagerEvent::Message(
+            id.clone(),
+            CommMsg::Data(json!({
+                "method": "focus",
+                "params": {
+                    "input": input_code
+                }
+            })),
+        ))?;
+        return Ok(R_NilValue);
+    }
+
+    let id = Uuid::new_v4().to_string();
+    *comm_id_guard = Some(id.clone());
+
+    ReticulateService::start(id, main.get_comm_manager_tx().clone())?;
+
+    Ok(R_NilValue)
+}