From 14c96090102be7dfd48c7811f85895d1f848b0d1 Mon Sep 17 00:00:00 2001
From: Hadley Wickham <h.wickham@gmail.com>
Date: Thu, 20 Jun 2024 16:02:03 +0100
Subject: [PATCH] Restore object that knitr uses (#162)

* Restore object that knitr uses

* Re-document
---
 R/eval.R        | 4 +++-
 R/zzz.R         | 6 ++++++
 man/evaluate.Rd | 2 +-
 3 files changed, 10 insertions(+), 2 deletions(-)
 create mode 100644 R/zzz.R

diff --git a/R/eval.R b/R/eval.R
index 7711afd..9c97a0b 100644
--- a/R/eval.R
+++ b/R/eval.R
@@ -47,12 +47,14 @@ evaluate <- function(input,
                      log_echo = FALSE,
                      log_warning = FALSE,
                      new_device = TRUE,
-                     output_handler = new_output_handler(),
+                     output_handler = NULL,
                      filename = NULL,
                      include_timing = FALSE) {
   stop_on_error <- as.integer(stop_on_error)
   stopifnot(length(stop_on_error) == 1)
 
+  output_handler <- output_handler %||% default_output_handler
+
   if (isTRUE(include_timing)) {
     warning("`evaluate(include_timing)` is deprecated")
   }
diff --git a/R/zzz.R b/R/zzz.R
new file mode 100644
index 0000000..ccc8811
--- /dev/null
+++ b/R/zzz.R
@@ -0,0 +1,6 @@
+# used by knitr to avoid overheard of calling new_output_handler() repeatedly
+default_output_handler <- NULL
+
+.onLoad <- function(...) {
+  default_output_handler <<- new_output_handler()
+}
diff --git a/man/evaluate.Rd b/man/evaluate.Rd
index 9093d1a..d76f7ba 100644
--- a/man/evaluate.Rd
+++ b/man/evaluate.Rd
@@ -15,7 +15,7 @@ evaluate(
   log_echo = FALSE,
   log_warning = FALSE,
   new_device = TRUE,
-  output_handler = new_output_handler(),
+  output_handler = NULL,
   filename = NULL,
   include_timing = FALSE
 )