Preserve aesthetics in colourbar merge

NEWS.md

@@ -54,6 +54,8 @@
  * `guide_coloursteps()` and `guide_bins()` sort breaks (#5152).
  * `guide_axis()` gains a `cap` argument that can be used to trim the
  axis line to extreme breaks (#4907).
+ * `guide_colourbar()` and `guide_coloursteps()` merge properly when one
+ of aesthetics is dropped (#5324).
 
 * `geom_label()` now uses the `angle` aesthetic (@teunbrand, #2785)
 * 'lines' units in `geom_label()`, often used in the `label.padding` argument, 

R/guide-colorbar.R

@@ -370,6 +370,8 @@ GuideColourbar <- ggproto(
  },
 
  merge = function(self, params, new_guide, new_params) {
+ new_params$key$.label <- new_params$key$.value <- NULL
+ params$key <- vec_cbind(params$key, new_params$key)
  return(list(guide = self, params = params))
  },
 

tests/testthat/test-guides.R

@@ -311,6 +311,26 @@ test_that("guide_coloursteps and guide_bins return ordered breaks", {
  expect_true(all(diff(key$.value) < 0))
 })
 
+test_that("guide_colourbar merging preserves both aesthetics", {
+ # See issue 5324
+
+ scale1 <- scale_colour_viridis_c()
+ scale1$train(c(0, 2))
+
+ scale2 <- scale_fill_viridis_c()
+ scale2$train(c(0, 2))
+
+ g <- guide_colourbar()
+ p <- g$params
+
+ p1 <- g$train(p, scale1, "colour")
+ p2 <- g$train(p, scale2, "fill")
+
+ merged <- g$merge(p1, g, p2)
+
+ expect_true(all(c("colour", "fill") %in% names(merged$params$key)))
+})
+
 # Visual tests ------------------------------------------------------------
 
 test_that("axis guides are drawn correctly", {