check for unknown labels

Author: teunbrand

R/labels.R

@@ -18,8 +18,8 @@ update_labels <- function(p, labels) {
 
 # Called in `ggplot_build()` to set default labels not specified by user.
 setup_plot_labels <- function(plot, layers, data) {
-  # Initiate from user-defined labels
-  labels <- plot$labels
+  # Initiate empty labels
+  labels <- list()
 
   # Find labels from every layer
   for (i in seq_along(layers)) {
@@ -63,7 +63,26 @@ setup_plot_labels <- function(plot, layers, data) {
       labels <- defaults(labels, current)
     }
   }
-  labels
+
+  # Warn for spurious labels that don't have a mapping.
+  # Note: sometimes, 'x' and 'y' might not have a mapping, like in
+  # `geom_function()`. We can display these labels anyway, so we include them.
+  plot_labels  <- plot$labels
+  known_labels <- c(names(labels), fn_fmls_names(labs), "x", "y")
+  extra_labels <- setdiff(names(plot_labels), known_labels)
+
+  if (length(extra_labels) > 0) {
+    extra_labels <- paste0(
+      "{.code ", extra_labels, " = \"", plot_labels[extra_labels], "\"}"
+    )
+    names(extra_labels) <- rep("*", length(extra_labels))
+    cli::cli_warn(c(
+      "Ignoring unknown labels:",
+      extra_labels
+    ))
+  }
+
+  defaults(plot_labels, labels)
 }
 
 #' Modify axis, legend, and plot labels

tests/testthat/_snaps/labels.md

@@ -12,6 +12,11 @@
     * foo = "bar"
     i Did you misspell an argument name?
 
+# warnings are thrown for unknown labels
+
+    Ignoring unknown labels:
+    * `foo = "bar"`
+
 # plot.tag.position rejects invalid input
 
     The `plot.tag.position` theme element must be a <character/numeric/integer> object.

tests/testthat/test-labels.R

@@ -93,6 +93,11 @@ test_that("get_alt_text checks dots", {
   expect_snapshot_warning(get_alt_text(ggplot(), foo = "bar"))
 })
 
+test_that("warnings are thrown for unknown labels", {
+  p <- ggplot(mtcars, aes(mpg, disp)) + geom_point() + labs(foo = 'bar')
+  expect_snapshot_warning(ggplot_build(p))
+})
+
 test_that("plot.tag.position rejects invalid input", {
   p <- ggplot(mtcars, aes(mpg, disp)) + geom_point() + labs(tag = "Fig. A)")