set_theme() resets theme if called with no arguments. (#6629)

Fixes #6598

Author: VisruthSK

R/theme-current.R

@@ -91,9 +91,10 @@ get_theme <- function() {
 theme_get <- get_theme
 
 #' @rdname get_theme
-#' @param new new theme (a list of theme elements)
+#' @param new new theme (a list of theme elements). Sets theme to the default ([theme_grey()]) if `new` isn't supplied.
 #' @export
-set_theme <- function(new) {
+set_theme <- function(new = NULL) {
+  new <- new %||% ggplot_global$theme_default
   check_object(new, is_theme, "a {.cls theme} object")
   old <- ggplot_global$theme_current
   ggplot_global$theme_current <- new
@@ -141,4 +142,3 @@ theme_replace <- replace_theme
 
   e1
 }
-

man/get_theme.Rd

@@ -56,6 +56,12 @@ test_that("modifying theme element properties with + operator works", {
   )
 })
 
+test_that("set_theme() resets theme to default when called with no arguments", {
+  theme_set(theme_void())
+  set_theme()
+  expect_identical(theme_get(), theme_grey())
+})
+
 test_that("adding theme object to ggplot object with + operator works", {
   ## test with complete theme
   p <- ggplot(data.frame(x = 1:3), aes(x, x)) + geom_point() + theme_grey()