Warn when x/xmin are absent

Author: teunbrand

R/position-dodge.R

@@ -106,6 +106,11 @@ PositionDodge <- ggproto("PositionDodge", Position,
   reverse = NULL,
   setup_params = function(self, data) {
     flipped_aes <- has_flipped_aes(data, default = self$orientation == "y")
+    check_required_aesthetics(
+      if (flipped_aes) "y|ymin" else "x|xmin",
+      names(data), snake_class(self)
+    )
+
     data <- flip_data(data, flipped_aes)
     if (is.null(data$xmin) && is.null(data$xmax) && is.null(self$width)) {
       cli::cli_warn(c(

tests/testthat/test-position_dodge.R

@@ -37,3 +37,19 @@ test_that("position_dodge() can reverse the dodge order", {
   ld <- get_layer_data(p + geom_col(position = position_dodge(reverse = FALSE)))
   expect_equal(ld$label[order(ld$x)], c("A", "A", "B", "B", "C"))
 })
+
+test_that("position_dodge warns about missing required aesthetics", {
+
+  # Bit of a contrived geom to not have a required 'x' aesthetic
+  GeomDummy <- ggproto(NULL, GeomPoint, required_aes = NULL, optional_aes = "x")
+
+  p <- ggplot(mtcars, aes(cyl, disp, colour = factor(vs))) +
+    layer(
+      geom = GeomDummy,
+      stat = "identity",
+      position = position_dodge(width = 0.5),
+      mapping = aes(x = NULL)
+    )
+
+  expect_error(ggplot_build(p), "requires the following missing aesthetics")
+})