Manual scale limits default to present names of values

NEWS.md

@@ -1,5 +1,11 @@
 # ggplot2 (development version)
 
+* `scale_*_manual()` no longer displays extra legend keys, or changes their 
+  order, when a named `values` argument has more items than the data. To display
+  all `values` on the legend instead, use
+  `scale_*_manual(values = vals, limits = names(vals))`. (@teunbrand, @banfai, 
+  #4511, #4534)
+
 # ggplot2 3.3.5
 This is a very small release focusing on fixing a couple of untenable issues 
 that surfaced with the 3.3.4 release

R/scale-manual.r

@@ -132,8 +132,9 @@ manual_scale <- function(aesthetic, values = NULL, breaks = waiver(), ..., limit
     force(values)
   }
 
-  if (is.null(limits)) {
-    limits <- names(values)
+  if (is.null(limits) && !is.null(names(values))) {
+    # Limits as function to access `values` names later on (#4619)
+    limits <- function(x) intersect(x, names(values))
   }
 
   # order values according to breaks

tests/testthat/test-scale-manual.r

@@ -117,7 +117,7 @@ test_that("fewer values (#3451)", {
 test_that("limits and breaks (#4619)", {
   # values don't change legend order
   s1 <- scale_colour_manual(
-    values = c("8" = "c", "4" = "a", "6" = "b"),
+    values = c("8" = "c", "4" = "a", "6" = "b")
   )
   s1$train(c("8", "6", "4"))
   expect_equal(s1$map(c("8", "6", "4")), c("c", "b", "a"))