Resource namespaces only after debug() or debugonce() calls

Author: lionel-

crates/ark/src/interface.rs

@@ -2057,7 +2057,10 @@ fn do_resource_namespaces() -> bool {
     let opt: Option<bool> = r_null_or_try_into(harp::get_option("ark.resource_namespaces"))
         .ok()
         .flatten();
-    opt.unwrap_or(true)
+
+    // By default we don't resource namespaces to avoid increased memory usage.
+    // https://github.com/posit-dev/positron/issues/5050
+    opt.unwrap_or(false)
 }
 
 /// Are we auto-printing?

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

@@ -7,6 +7,8 @@
 
 register_hooks <- function() {
     rebind("utils", "View", .ps.view_data_frame, namespace = TRUE)
+    rebind("base", "debug", new_ark_debug(base::debug), namespace = TRUE)
+    rebind("base", "debugonce", new_ark_debug(base::debugonce), namespace = TRUE)
     register_getHook_hook()
 }
 

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

@@ -44,3 +44,35 @@ reparse_with_srcref <- function(x, name, uri, line) {
 zap_srcref <- function(x) {
     .ps.Call("ark_zap_srcref", x)
 }
+
+new_ark_debug <- function(fn) {
+  # Signature of `debug()`:
+  # function(fun, text = "", condition = NULL, signature = NULL)
+
+  body(fn) <- bquote({
+    local({
+        # Don't do anything if user has explicitly disabled namespace resourcing
+        if (!.ps.internal(do_resource_namespaces(default = TRUE))) {
+            return() # from local()
+        }
+
+        # Enable namespace resourcing for all future loaded namespaces and
+        # resource already loaded namespaces so we get virtual documents for
+        # step-debugging.
+        options(ark.resource_namespaces = TRUE)
+        .ps.internal(resource_loaded_namespaces())
+    })
+
+    .(body(fn))
+  })
+
+  fn
+}
+
+do_resource_namespaces <- function(default) {
+    getOption("ark.resource_namespaces", default = default)
+}
+
+resource_loaded_namespaces <- function() {
+    .ps.Call("ps_resource_loaded_namespaces")
+}

crates/ark/src/srcref.rs

@@ -31,6 +31,12 @@ pub(crate) fn resource_loaded_namespaces() -> anyhow::Result<()> {
     Ok(())
 }
 
+#[harp::register]
+unsafe extern "C" fn ps_resource_loaded_namespaces() -> anyhow::Result<SEXP> {
+    resource_loaded_namespaces()?;
+    Ok(harp::r_null())
+}
+
 #[harp::register]
 unsafe extern "C" fn ps_ns_populate_srcref(ns_name: SEXP) -> anyhow::Result<SEXP> {
     let ns_name: String = RObject::view(ns_name).try_into()?;