Recognise empty scale with limits = <function> as empty (#5948)

* discrete scale is also empty when limits is a function

* add news bullet

Author: teunbrand

NEWS.md

@@ -127,6 +127,8 @@
 * New function `get_strip_labels()` to retrieve facet labels (@teunbrand, #4979)
 * Fixed bug in `position_dodge2()`'s identification of range overlaps 
   (@teunbrand, #5938, #4327).
+* Fixed bug where empty discrete scales weren't recognised as such 
+  (@teunbrand, #5945).
 
 # ggplot2 3.5.1
 

R/scale-discrete-.R

@@ -130,7 +130,9 @@ ScaleDiscretePosition <- ggproto("ScaleDiscretePosition", ScaleDiscrete,
   },
 
   is_empty = function(self) {
-    is.null(self$range$range) && is.null(self$limits) && is.null(self$range_c$range)
+    is.null(self$range$range) &&
+      (is.null(self$limits) || is.function(self$limits)) &&
+      is.null(self$range_c$range)
   },
 
   reset = function(self) {