Better message in facetted_pos_scales #91

R/facetted_pos_scales.R

@@ -89,7 +89,20 @@ facetted_pos_scales <- function(x = NULL, y = NULL) {
   x_test <- check_facetted_scale(x, "x")
   y_test <- check_facetted_scale(y, "y")
   if (!(x_test & y_test)) {
-    stop("Invalid facetted scale specifications.")
+    if (!x_test & !y_test) {
+      arg  <- "The {.arg x} and {.arg y} arguments "
+      type <- "appropriate"
+    } else if (!x_test) {
+      arg  <- "The {.arg x} argument "
+      type <- "{.field x}"
+    } else {
+      arg  <- "The {.arg y} argument "
+      type <- "{.field y}"
+    }
+    cli::cli_abort(paste0(
+      arg, "should be {.val NULL}, or a list of formulas and/or ",
+      "position scales with the ", type, " aesthetic."
+    ))
   }
 
   x <- validate_facetted_scale(x, "x")

tests/testthat/_snaps/facetted_pos_scales.md

@@ -0,0 +1,8 @@
+# facetted_pos_scales warns about invalid scales
+
+    The `x` argument should be "NULL", or a list of formulas and/or position scales with the x aesthetic.
+
+---
+
+    The `y` argument should be "NULL", or a list of formulas and/or position scales with the y aesthetic.
+

tests/testthat/test-facetted_pos_scales.R

@@ -346,16 +346,14 @@ test_that("facetted_pos_scales can handle date scales", {
 test_that("facetted_pos_scales warns about invalid scales", {
 
   # Nonsensical input
-  test <- substitute(facetted_pos_scales(y = list(
-    NULL, scale_y_continuous(), "nonsense")
-  ))
-  expect_error(eval(test), "Invalid facetted scale")
+  expect_snapshot_error(
+    facetted_pos_scales(x = list(NULL, scale_x_continuous(), "nonsense"))
+  )
 
   # Incompatible aesthetics (x-scale to y-argument)
-  test <- substitute(facetted_pos_scales(y = list(
-    NULL, scale_x_continuous()
-  )))
-  expect_error(eval(test), "Invalid facetted scale")
+  expect_snapshot_error(
+    facetted_pos_scales(y = list(NULL, scale_x_continuous()))
+  )
 })
 
 test_that("facetted_pos_scales warns about invalid scales in formulas", {