Declare that we are in debug mode if any frame is marked with RDEBUG (#346)

Author: DavisVaughan

crates/ark/src/interface.rs

@@ -72,6 +72,7 @@ use harp::routines::r_register_routines;
 use harp::session::r_traceback;
 use harp::utils::r_get_option;
 use harp::utils::r_is_data_frame;
+use harp::utils::r_pairlist_any;
 use harp::utils::r_poke_option_show_error_messages;
 use harp::R_MAIN_THREAD_ID;
 use libr::R_BaseNamespace;
@@ -745,15 +746,19 @@ impl RMain {
         let prompt_slice = unsafe { CStr::from_ptr(prompt_c) };
         let prompt = prompt_slice.to_string_lossy().into_owned();
 
-        // Detect browser prompts by inspecting the `RDEBUG` flag of the
-        // last frame on the stack. This is not 100% infallible, for
-        // instance `debug(readline)` followed by `n` will instantiate a
-        // user request prompt that will look like a browser prompt
-        // according to this heuristic. However it has the advantage of
-        // correctly detecting that continue prompts are top-level browser
-        // prompts in case of incomplete inputs within `browser()`.
-        let frame = harp::session::r_sys_frame(n_frame).unwrap();
-        let browser = harp::session::r_env_is_browsed(frame).unwrap();
+        // Detect browser prompts by inspecting the `RDEBUG` flag of each
+        // frame on the stack. If ANY of the frames are marked with `RDEBUG`,
+        // then we assume we are in a debug state. We can't just check the
+        // last frame, as sometimes frames are pushed onto the stack by lazy
+        // evaluation of arguments or `tryCatch()` that aren't debug frames,
+        // but we don't want to exit the debugger when we hit these, as R is
+        // still inside a browser state. Should also handle cases like `debug(readline)`
+        // followed by `n`.
+        // https://github.com/posit-dev/positron/issues/2310
+        let frames = RObject::from(harp::session::r_sys_frames().unwrap());
+        let browser = r_pairlist_any(frames.sexp, |frame| {
+            harp::session::r_env_is_browsed(frame).unwrap()
+        });
 
         // 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()`

crates/harp/src/object.rs

@@ -266,6 +266,16 @@ pub fn r_alloc_list(size: R_xlen_t) -> SEXP {
     unsafe { Rf_allocVector(VECSXP, size) }
 }
 
+pub fn r_node_car(x: SEXP) -> SEXP {
+    unsafe { CAR(x) }
+}
+pub fn r_node_tag(x: SEXP) -> SEXP {
+    unsafe { TAG(x) }
+}
+pub fn r_node_cdr(x: SEXP) -> SEXP {
+    unsafe { CDR(x) }
+}
+
 impl RObject {
     pub unsafe fn new(data: SEXP) -> Self {
         RObject {

crates/harp/src/utils.rs

@@ -30,6 +30,8 @@ use crate::object::r_chr_get;
 use crate::object::r_chr_poke;
 use crate::object::r_dim;
 use crate::object::r_length;
+use crate::object::r_node_car;
+use crate::object::r_node_cdr;
 use crate::object::r_str_blank;
 use crate::object::r_str_na;
 use crate::object::RObject;
@@ -660,6 +662,26 @@ pub unsafe fn r_ns_env_name(env: SEXP) -> SEXP {
     STRING_ELT(spec, 0)
 }
 
+/// Returns `true` if `f` returns `true` for any node of the pairlist
+pub fn r_pairlist_any<F>(x: SEXP, f: F) -> bool
+where
+    F: Fn(SEXP) -> bool,
+{
+    let mut node = x;
+
+    while node != r_null() {
+        let elt = r_node_car(node);
+
+        if f(elt) {
+            return true;
+        }
+
+        node = r_node_cdr(node);
+    }
+
+    return false;
+}
+
 pub unsafe fn r_try_eval_silent(x: SEXP, env: SEXP) -> Result<SEXP> {
     let mut errc = 0;