Record backtraces for 5 first warnings

R/conditions.R

@@ -265,13 +265,18 @@ new_dplyr_warning <- function(data) {
   warning_cnd(
     message = msg,
     parent = data$cnd,
-    call = data$call
+    call = data$call,
+    trace = data$cnd$trace
   )
 }
 
 #' @export
 print.dplyr_last_warnings <- function(x, ...) {
-  print(unstructure(x), ...)
+  # Opt into experimental grayed out tree
+  local_options(
+    "rlang:::trace_display_tree" = TRUE
+  )
+  print(unstructure(x), ..., simplify = "none")
 
   remaining <- attr(x, "remaining")
   if (remaining) {

R/mutate.R

@@ -260,6 +260,12 @@ mutate_cols <- function(.data, dots, caller_env, error_call = caller_env()) {
       )
     },
     warning = function(w) {
+      # Don't entrace more than 5 warnings because this is very costly
+      if (is_null(w$trace) && length(warnings) <= 5) {
+        # The frame skipping assumes a regular `base::warning()` stack.
+        # Also works with warnings emitted from C with `Rf_warning()`.
+        w$trace <- trace_back(bottom = sys.frame(-5))
+      }
       new <- cnd_data(
         cnd = w,
         error_ctxt,