Skip viewscales if graticule is empty

NEWS.md

@@ -1,5 +1,6 @@
 # ggplot2 (development version)
 
+* `coord_sf()` no longer errors when dealing with empty graticules (@teunbrand, #6052)
 * Passing empty unmapped aesthetics to layers raises a warning instead of
   throwing an error (@teunbrand, #6009).
 * Moved {mgcv} from Imports to Suggests (@teunbrand, #5986)

R/coord-sf.R

@@ -658,6 +658,9 @@ sf_breaks <- function(scale_x, scale_y, bbox, crs) {
 #' @keywords internal
 view_scales_from_graticule <- function(graticule, scale, aesthetic,
                                        label, label_graticule, bbox) {
+  if (empty(graticule)) {
+    return(ggproto(NULL, ViewScale))
+  }
 
   # Setup position specific parameters
   # Note that top/bottom doesn't necessarily mean to label the meridians and

tests/testthat/test-coord_sf.R

@@ -371,3 +371,27 @@ test_that("coord_sf() throws error when limits are badly specified", {
   # throws error when limit's length is different than two
   expect_snapshot_error(ggplot() + coord_sf(ylim=1:3))
 })
+
+test_that("coord_sf() can render with empty graticules", {
+
+  skip_if_not_installed("sf")
+  # Skipping this test on CRAN as changes upstream in {sf} might affect
+  # this test, i.e. when suddenly graticules *do* work
+  skip_on_cran()
+
+  df <- sf::st_sf(
+    g = sf::st_sfc(sf::st_point(
+      # Out of bounds values for lon/lat
+      c(-600, 1200)
+    )),
+    crs = 4326
+  )
+
+  # Double-check graticule is empty, suppressing warnings about oob longlat values
+  grat <- suppressWarnings(sf::st_graticule(df))
+  expect_equal(nrow(grat), 0)
+
+  # Plot should render
+  p <- suppressWarnings(layer_grob(ggplot(df) + geom_sf())[[1]])
+  expect_length(p$x, 1)
+})