fix rstudio/rmarkdown#2363: ignore empty plots that only contain call…

…s to requireNamespace()

DESCRIPTION

@@ -1,7 +1,7 @@
 Package: evaluate
 Type: Package
 Title: Parsing and Evaluation Tools that Provide More Details than the Default
-Version: 0.15.1
+Version: 0.15.2
 Authors@R: c(
     person("Hadley", "Wickham", role = "aut"),
     person("Yihui", "Xie", role = c("aut", "cre"), email = "[email protected]", comment = c(ORCID = "0000-0003-0645-5666")),
@@ -28,6 +28,6 @@ Suggests:
     ggplot2,
     lattice,
     testthat
-RoxygenNote: 7.1.1
+RoxygenNote: 7.2.0
 Encoding: UTF-8
 Roxygen: list(markdown = TRUE)

NEWS.md

@@ -1,6 +1,7 @@
 Version 0.16
 ================================================================================
 
+- Fixed a bug that an empty **ggplot2** plot could be recorded and incorrectly saved (thanks, @sjspielman, rstudio/rmarkdown#2363).
 
 Version 0.15
 ================================================================================

R/graphics.r

@@ -61,9 +61,11 @@ is.empty <- function(x) {
 plot_calls <- function(plot) {
   el <- lapply(plot[[1]], "[[", 2)
   if (length(el) == 0) return()
-  sapply(el, function(x) {
-    x <- x[[1]]
-    # grid graphics do not have x$name
-    if (is.null(x[["name"]])) deparse(x) else x[["name"]]
-  })
+  unlist(lapply(el, function(x) {
+    # grid graphics do not have x[[1]]$name
+    if (!is.null(nm <- x[[1]][["name"]])) return(nm)
+    nm <- deparse(x[[1]])
+    # the plot element should not be empty
+    if (length(x[[2]]) > 0 || !grepl("^requireNamespace\\(", nm)) nm
+  }))
 }