From c84a16a78ebf62270a5046cd07a81d50b375b31f Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 22 Aug 2025 10:04:35 +0200
Subject: [PATCH 1/2] return plot as-is when default coords are added to user
 coords

---
 R/plot-construction.R | 6 ++++++
 1 file changed, 6 insertions(+)

diff --git a/R/plot-construction.R b/R/plot-construction.R
index 188e5cc574..10cebca7eb 100644
--- a/R/plot-construction.R
+++ b/R/plot-construction.R
@@ -200,6 +200,12 @@ S7::method(update_ggplot, list(class_theme, class_ggplot)) <-
 S7::method(update_ggplot, list(class_coord, class_ggplot)) <-
   function(object, plot, ...) {
     if (!isTRUE(plot@coordinates$default)) {
+
+      if (isTRUE(object$default)) {
+        # We don't let default coords override non-default coords (#6572)
+        return(plot)
+      }
+
       cli::cli_inform(c(
         "Coordinate system already present.",
         i = "Adding new coordinate system, which will replace the existing one."

From 967a64756604dc66ef6054575f88308f369bd88f Mon Sep 17 00:00:00 2001
From: Teun van den Brand <tahvdbrand@gmail.com>
Date: Fri, 22 Aug 2025 10:04:53 +0200
Subject: [PATCH 2/2] add tests

---
 tests/testthat/_snaps/coord-.md |  8 ++++++++
 tests/testthat/test-coord-.R    | 28 ++++++++++++++++++++++++++++
 2 files changed, 36 insertions(+)

diff --git a/tests/testthat/_snaps/coord-.md b/tests/testthat/_snaps/coord-.md
index 563c7f475d..d4c6991988 100644
--- a/tests/testthat/_snaps/coord-.md
+++ b/tests/testthat/_snaps/coord-.md
@@ -34,3 +34,11 @@
       Error:
       ! `1:3` must be a vector of length 2, not length 3.
 
+# adding default coords works correctly
+
+    Code
+      test <- test + coord_cartesian(xlim = c(-2, 2))
+    Message
+      Coordinate system already present.
+      i Adding new coordinate system, which will replace the existing one.
+
diff --git a/tests/testthat/test-coord-.R b/tests/testthat/test-coord-.R
index ea80cb5ce1..02ed6675ed 100644
--- a/tests/testthat/test-coord-.R
+++ b/tests/testthat/test-coord-.R
@@ -108,3 +108,31 @@ test_that("coord expand takes a vector", {
 
 })
 
+test_that("adding default coords works correctly", {
+
+  base <- ggplot() + coord_cartesian(default = TRUE, xlim = c(0, 1))
+
+  # default + user = user
+  expect_no_message(
+    test <- base + coord_cartesian(xlim = c(-1, 1))
+  )
+  expect_equal(test@coordinates$limits$x, c(-1, 1))
+
+  # user1 + user2 = user2 + message
+  expect_snapshot(
+    test <- test + coord_cartesian(xlim = c(-2, 2))
+  )
+  expect_equal(test@coordinates$limits$x, c(-2, 2))
+
+  # user + default = user
+  expect_no_message(
+    test <- test + coord_cartesian(xlim = c(-3, 3), default = TRUE)
+  )
+  expect_equal(test@coordinates$limits$x, c(-2, 2))
+
+  # default1 + default2 = default2 (silent)
+  expect_no_message(
+    test <- base + coord_cartesian(xlim = c(-4, 4), default = TRUE)
+  )
+  expect_equal(test@coordinates$limits$x, c(-4, 4))
+})