Duplicated aes warning with multiple modified aesthetics

DESCRIPTION

@@ -69,7 +69,7 @@ Suggests:
     rpart,
     sf (>= 0.7-3),
     svglite (>= 1.2.0.9001),
-    testthat (>= 3.0.0),
+    testthat (>= 3.1.2),
     vdiffr (>= 1.0.0),
     xml2
 Enhances: 

NEWS.md

@@ -1,5 +1,9 @@
 # ggplot2 (development version)
 
+* Using multiple modified aesthetics correctly will no longer trigger warnings. 
+  If used incorrectly, the warning will now report the duplicated aesthetic 
+  instead of `NA` (@teunbrand, #4707).
+
 * `...` supports `rlang::list2` dynamic dots in all public functions. (@mone27, #4764) 
 
 * `theme()` now has a `strip.clip` argument, that can be set to `"off"` to 

R/geom-.r

@@ -143,7 +143,7 @@ Geom <- ggproto("Geom",
         abort(msg)
       }
 
-      names(modified_aes) <- rename_aes(names(modifiers))
+      names(modified_aes) <- names(rename_aes(modifiers))
       modified_aes <- new_data_frame(compact(modified_aes))
 
       data <- cunion(modified_aes, data)

tests/testthat/_snaps/aes-calculated.md

@@ -0,0 +1,8 @@
+# staged aesthetics warn appropriately for duplicated names
+
+    Duplicated aesthetics after name standardisation: colour
+
+---
+
+    Duplicated aesthetics after name standardisation: colour
+

tests/testthat/test-aes-calculated.r

@@ -49,3 +49,23 @@ test_that("make_labels() deprases mappings properly", {
   expect_identical(make_labels(aes(x = 1)), list(x = "x"))
   expect_identical(make_labels(aes(x = NULL)), list(x = "x"))
 })
+
+test_that("staged aesthetics warn appropriately for duplicated names", {
+  # Test should *not* report `NA` as the duplicated aes (#4707)
+  df <- data.frame(x = 1, y = 1, lab = "test")
+
+  # One warning in plot code due to evaluation of `aes()`
+  expect_snapshot_warning(
+    p <- ggplot(df, aes(x, y, label = lab)) +
+      geom_label(
+        aes(colour = stage(lab, after_scale = colour),
+            color  = after_scale(color))
+      ) +
+      # Guide would trigger another warning when plot is printed, due to the
+      # `guide_geom.legend` also using `Geom$use_defaults` method, which we
+      # test next
+      guides(colour = "none")
+  )
+  # One warning in building due to `stage()`/`after_scale()`
+  expect_snapshot_warning(ggplot_build(p))
+})