From 76b102703cc7a65c8f7f8302acba7c01c2e0c1d9 Mon Sep 17 00:00:00 2001
From: Lionel Henry <lionel.hry@gmail.com>
Date: Wed, 21 Jun 2023 12:21:08 +0200
Subject: [PATCH] Use `nframe()` to detect prompts like `readline()`

---
 crates/ark/src/interface.rs | 26 +++++++++++++++++++-------
 crates/harp/src/lib.rs      |  3 ++-
 crates/harp/src/session.rs  | 36 ++++++++++++++++++++++++++++++++++++
 3 files changed, 57 insertions(+), 8 deletions(-)
 create mode 100644 crates/harp/src/session.rs

diff --git a/crates/ark/src/interface.rs b/crates/ark/src/interface.rs
index 5e7f58885..de6282589 100644
--- a/crates/ark/src/interface.rs
+++ b/crates/ark/src/interface.rs
@@ -309,17 +309,29 @@ pub struct PromptInfo {
 }
 
 fn prompt_info(prompt_c: *const c_char) -> PromptInfo {
+    let n_frame = unwrap!(harp::session::r_n_frame(), Err(err) => {
+        warn!("`r_n_frame()` failed: {}", err);
+        0
+    });
+    trace!("prompt_info(): n_frame = '{}'", n_frame);
+
     let prompt_slice = unsafe { CStr::from_ptr(prompt_c) };
     let prompt = prompt_slice.to_string_lossy().into_owned();
 
-    // The request is incomplete if we see the continue prompt
-    let continue_prompt = unsafe { r_get_option::<String>("continue").unwrap() };
-    let incomplete = prompt == continue_prompt;
+    // TODO: Detect with `env_is_browsed(sys.frame(sys.nframe()))`
+    let browser = false;
 
-    // If the current prompt doesn't match the default prompt, assume that
-    // we're reading use input, e.g. via 'readline()'.
-    let default_prompt = unsafe { r_get_option::<String>("prompt").unwrap() };
-    let user_request = !incomplete && prompt != default_prompt;
+    // If there are frames on the stack and we're not in a browser prompt,
+    // this means some user code is requesting input, e.g. via `readline()`
+    let user_request = !browser && n_frame > 0;
+
+    // The request is incomplete if we see the continue prompt, except if
+    // we're in a user request, e.g. `readline("+ ")`
+    let continue_prompt = unwrap!(unsafe { r_get_option::<String>("continue") }, Err(err) => {
+        warn!("`r_get_option()` failed: {}", err);
+        String::from("+ ")
+    });
+    let incomplete = !user_request && prompt == continue_prompt;
 
     if incomplete {
         trace!("Got R prompt '{}', marking request incomplete", prompt);
diff --git a/crates/harp/src/lib.rs b/crates/harp/src/lib.rs
index 3439a34a5..3b27953bd 100644
--- a/crates/harp/src/lib.rs
+++ b/crates/harp/src/lib.rs
@@ -14,6 +14,7 @@ pub mod lock;
 pub mod object;
 pub mod protect;
 pub mod routines;
+pub mod session;
 pub mod string;
 pub mod symbol;
 pub mod test;
@@ -162,7 +163,7 @@ macro_rules! r_lang {
 
     ($($tts:tt)*) => {{
         let value = $crate::r_pairlist!($($tts)*);
-        libR_sys::SET_TYPEOF(value, LISTSXP as i32);
+        libR_sys::SET_TYPEOF(value, LANGSXP as i32);
         value
     }}
 
diff --git a/crates/harp/src/session.rs b/crates/harp/src/session.rs
new file mode 100644
index 000000000..e3c7a65bf
--- /dev/null
+++ b/crates/harp/src/session.rs
@@ -0,0 +1,36 @@
+//
+// session.rs
+//
+// Copyright (C) 2023 Posit Software, PBC. All rights reserved.
+//
+//
+
+use std::sync::Once;
+
+use libR_sys::*;
+
+use crate::utils::r_try_eval_silent;
+use crate::vector::integer_vector::IntegerVector;
+use crate::vector::Vector;
+
+pub fn r_n_frame() -> crate::error::Result<i32> {
+    SESSION_INIT.call_once(init_interface);
+
+    unsafe {
+        let ffi = r_try_eval_silent(NFRAME_CALL as SEXP, R_BaseEnv)?;
+        let n_frame = IntegerVector::new(ffi)?;
+        Ok(n_frame.get_unchecked_elt(0))
+    }
+}
+
+// Globals
+static SESSION_INIT: Once = Once::new();
+static mut NFRAME_CALL: usize = 0;
+
+fn init_interface() {
+    unsafe {
+        let nframe_call = crate::r_lang!(crate::r_symbol!("sys.nframe"));
+        R_PreserveObject(nframe_call);
+        NFRAME_CALL = nframe_call as usize;
+    }
+}