From 9f1f73f81bd99110e363ac4f166d7e86f7f1c13d Mon Sep 17 00:00:00 2001
From: Teun van den Brand <49372158+teunbrand@users.noreply.github.com>
Date: Sat, 17 Jun 2023 10:50:53 +0200
Subject: [PATCH] Preserve aesthetics in colourbar merge

---
 NEWS.md                      |  2 ++
 R/guide-colorbar.R           |  2 ++
 tests/testthat/test-guides.R | 20 ++++++++++++++++++++
 3 files changed, 24 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index 7a9eb66130..7a79bff0c6 100644
--- a/NEWS.md
+++ b/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, 
diff --git a/R/guide-colorbar.R b/R/guide-colorbar.R
index 65291f37cc..d4707f0380 100644
--- a/R/guide-colorbar.R
+++ b/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))
   },
 
diff --git a/tests/testthat/test-guides.R b/tests/testthat/test-guides.R
index 4ef7174f99..a162dcb7b2 100644
--- a/tests/testthat/test-guides.R
+++ b/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", {