check type for date_breaks and date_minor_breaks

NEWS.md

@@ -1,5 +1,7 @@
 # ggplot2 (development version)
 
+* Date(time) scales now throw appropriate errors when `date_breaks`, 
+  `date_minor_breaks` or `date_labels` are not strings (@RodDalBen, #5880)
 * The `summary()` method for ggplots is now more terse about facets 
   (@teunbrand, #5989).
 * `guide_bins()`, `guide_colourbar()` and `guide_coloursteps()` gain an `angle`

R/scale-date.R

@@ -303,12 +303,15 @@ datetime_scale <- function(aesthetics, transform, trans = deprecated(),
   if (is.character(minor_breaks)) minor_breaks <- breaks_width(minor_breaks)
 
   if (!is.waive(date_breaks)) {
+    check_string(date_breaks)
     breaks <- breaks_width(date_breaks)
   }
   if (!is.waive(date_minor_breaks)) {
+    check_string(date_minor_breaks)
     minor_breaks <- breaks_width(date_minor_breaks)
   }
   if (!is.waive(date_labels)) {
+    check_string(date_labels)
     labels <- function(self, x) {
       tz <- self$timezone %||% "UTC"
       label_date(date_labels, tz)(x)

tests/testthat/test-scale-date.R

@@ -69,7 +69,7 @@ test_that("datetime colour scales work", {
   expect_equal(range(get_layer_data(p)$colour), c("#132B43", "#56B1F7"))
 })
 
-test_that("date(time) scales throw warnings when input is numeric", {
+test_that("date(time) scales throw warnings when input is incorrect", {
   p <- ggplot(data.frame(x = 1, y = 1), aes(x, y)) + geom_point()
 
   expect_warning(
@@ -82,4 +82,19 @@ test_that("date(time) scales throw warnings when input is numeric", {
     "The value was converted to a <POSIXt/POSIXct> object."
   )
 
+  expect_error(
+    ggplot_build(p + scale_x_date(date_breaks = c(11, 12))),
+    "must be a single string"
+  )
+
+  expect_error(
+    ggplot_build(p + scale_x_date(date_minor_breaks = c(11, 12))),
+    "must be a single string"
+  )
+
+  expect_error(
+    ggplot_build(p + scale_x_date(date_labels = c(11, 12))),
+    "must be a single string"
+  )
+
 })