Domesticate NULL aesthetic labels (#6644)

* labels derived from NULL aesthetics serve only as fallback labels

* catch tests where this occurs

* add news bullet

* atomic vectors also produce fallback labels

* move `make_labels()` helper to file where it is used

* update test

* fix guide order in unrelated test

Author: teunbrand

NEWS.md

@@ -22,6 +22,8 @@
   not passed as the `name` argument (@teunbrand, #6623)
 * Fixed issue where vectorised `arrow()`s caused errors in drawing the 
   legend glyphs (@teunbrand, #6594)
+* Fixed regression where `NULL`-aesthetics contributed to plot labels too 
+  insistently. Now they contribute only as fallback labels (@teunbrand, #6616)
 
 # ggplot2 4.0.0
 

R/aes-evaluation.R

@@ -346,26 +346,6 @@ strip_stage <- function(expr) {
   }
 }
 
-# Convert aesthetic mapping into text labels
-make_labels <- function(mapping) {
-  default_label <- function(aesthetic, mapping) {
-    # e.g., geom_smooth(aes(colour = "loess")) or aes(y = NULL)
-    if (is.null(mapping) || is.atomic(mapping)) {
-      return(aesthetic)
-    }
-    mapping <- strip_stage(mapping)
-    mapping <- strip_dots(mapping, strip_pronoun = TRUE)
-    if (is_quosure(mapping) && quo_is_symbol(mapping)) {
-      name <- as_string(quo_get_expr(mapping))
-    } else {
-      name <- quo_text(mapping)
-      name <- gsub("\n.*$", "...", name)
-    }
-    name
-  }
-  Map(default_label, names(mapping), mapping)
-}
-
 eval_aesthetics <- function(aesthetics, data, mask = NULL) {
 
   env <- child_env(base_env())

R/labels.R

@@ -120,6 +120,26 @@ setup_plot_labels <- function(plot, layers, data) {
   labs(!!!defaults(plot_labels, labels))
 }
 
+# Convert aesthetic mapping into text labels
+make_labels <- function(mapping) {
+  default_label <- function(aesthetic, mapping) {
+    # e.g., geom_smooth(aes(colour = "loess")) or aes(y = NULL)
+    if (is.null(mapping) || is.atomic(mapping)) {
+      return(structure(aesthetic, fallback = TRUE))
+    }
+    mapping <- strip_stage(mapping)
+    mapping <- strip_dots(mapping, strip_pronoun = TRUE)
+    if (is_quosure(mapping) && quo_is_symbol(mapping)) {
+      name <- as_string(quo_get_expr(mapping))
+    } else {
+      name <- quo_text(mapping)
+      name <- gsub("\n.*$", "...", name)
+    }
+    name
+  }
+  Map(default_label, names(mapping), mapping)
+}
+
 #' Modify axis, legend, and plot labels
 #'
 #' Good labels are critical for making your plots accessible to a wider

tests/testthat/test-aes-calculated.R

@@ -45,9 +45,11 @@ test_that("make_labels() deparses mappings properly", {
   x_lab <- make_labels(aes(x = 2 * x * exp(`coef 1` * x^2) * 2 * x * exp(`coef 1` * x^2) * 2 * x))$x
   expect_length(x_lab, 1L)
   expect_match(x_lab, "...$")
-  # if the mapping is a literal or NULL, the aesthetics is used
-  expect_identical(make_labels(aes(x = 1)), list(x = "x"))
-  expect_identical(make_labels(aes(x = NULL)), list(x = "x"))
+  fallback <- list(x = structure("x", fallback = TRUE))
+  # if the mapping is a literal or NULL, the aesthetics is used as fallback
+  expect_identical(make_labels(aes(x = 1)), fallback)
+  # NULL labels should only be used as fallback labels
+  expect_identical(make_labels(aes(x = NULL)), fallback)
 })
 
 test_that("staged aesthetics warn appropriately for duplicated names", {

tests/testthat/test-aes.R

@@ -102,7 +102,8 @@ test_that("quosures are squashed when creating default label for a mapping", {
 test_that("labelling doesn't cause error if aesthetic is NULL", {
   p <- ggplot(mtcars) + aes(x = NULL)
   labels <- ggplot_build(p)@plot@labels
-  expect_identical(labels$x, "x")
+  # NULL labels should only be used as fallback labels
+  expect_identical(labels$x, structure("x", fallback = TRUE))
 })
 
 test_that("aes standardises aesthetic names", {

tests/testthat/test-draw-key.R

@@ -110,7 +110,11 @@ test_that("keep_draw_key", {
       aes(colour = "line", alpha = "line"),
       show.legend = c("colour" = NA, alpha = TRUE)
     ) +
-    suppressWarnings(scale_alpha_discrete())
+    suppressWarnings(scale_alpha_discrete()) +
+    guides(
+      alpha  = guide_legend(order = 1),
+      colour = guide_legend(order = 2)
+    )
 
   expect_doppelganger("appropriate colour key with alpha key as lines", p)