Auto-entrace errors

R/evaluate.R

@@ -152,7 +152,7 @@
       ),
       eval_continue = function() TRUE,
       eval_stop = function() FALSE,
-      eval_error = function(cnd) {signalCondition(cnd); stop(cnd)}
+      eval_error = signal_error
     )
     watcher$check_devices()
 
@@ -167,6 +167,14 @@
   watcher$get()
 }
 
+signal_error <- function(cnd) {
+  signalCondition(cnd)
+  if (has_rlang) {
+    cnd <- rlang::cnd_entrace(cnd)
+  }
+  stop(cnd)
+}
+
 check_stop_on_error <- function(x) {
   if (is.numeric(x) && length(x) == 1 && !is.na(x)) {
     if (x == 0L) {

R/zzz.R

@@ -3,11 +3,15 @@
 # used by knitr, as above, but also for value handler
 default_output_handler <- NULL
 
+has_rlang <- FALSE
+
 .onLoad <- function(...) {
   evaluate_default_output_handler <<- new_output_handler()
   default_output_handler <<- new_output_handler()
   # Match knitr's expectations
   default_output_handler$value <<- function(x) {
     render(x, visible = TRUE, envir = parent.frame())
   }
+
+  has_rlang <<- requireNamespace("rlang", quietly = TRUE)
 }