Unknown theme elements throw warnings instead of errors (#5743)

* demote error to warning

* filter known elements

* adjust test

* add news bullet

Author: teunbrand

NEWS.md

@@ -12,6 +12,7 @@
 * Patterns and gradients are now also enabled in `geom_sf()` 
   (@teunbrand, #5716).
 * `stat_bin()` deals with non-finite breaks better (@teunbrand, #5665).
+* Theme elements that do not exist now throw warnings instead of errors (#5719).
 * Fixed bug in `coord_radial()` where full circles were not treated as such 
   (@teunbrand, #5750).
 * When legends detect the presence of values in a layer, `NA` is now detected

R/theme-elements.R

@@ -620,7 +620,8 @@ validate_element <- function(el, elname, element_tree, call = caller_env()) {
   eldef <- element_tree[[elname]]
 
   if (is.null(eldef)) {
-    cli::cli_abort("The {.var {elname}} theme element is not defined in the element hierarchy.", call = call)
+    cli::cli_warn("The {.var {elname}} theme element is not defined in the element hierarchy.", call = call)
+    return()
   }
 
   # NULL values for elements are OK

R/theme.R

@@ -575,7 +575,8 @@ plot_theme <- function(x, default = theme_get()) {
   # Check that all elements have the correct class (element_text, unit, etc)
   validate_theme(theme)
 
-  theme
+
+  theme[intersect(names(theme), names(get_element_tree()))]
 }
 
 #' Modify properties of an element in a theme object

tests/testthat/test-theme.R

@@ -293,7 +293,7 @@ test_that("incorrect theme specifications throw meaningful errors", {
 test_that("element tree can be modified", {
   # we cannot add a new theme element without modifying the element tree
   p <- ggplot() + theme(blablabla = element_text(colour = "red"))
-  expect_snapshot_error(print(p))
+  expect_snapshot_warning(print(p))
 
   register_theme_elements(
     element_tree = list(blablabla = el_def("character", "text"))