Coord sf breaks fallback (#6232)

* add news bullet

* fallback

* avoid duplicated labels

* add test

* add news bullet

Author: teunbrand

NEWS.md

@@ -1,5 +1,9 @@
 # ggplot2 (development version)
 
+* Axis labels are now preserved better when using `coord_sf(expand = TRUE)` and
+  graticule lines are straight but do not meet the edge (@teunbrand, #2985).
+* Attempt to boost detail in `coord_polar()` and `coord_radial()` near the 
+  center (@teunbrand, #5023)
 * Scale names, guide titles and aesthetic labels can now accept functions 
   (@teunbrand, #4313)
 * Binned scales with zero-width data expand the default limits by 0.1 

R/coord-sf.R

@@ -721,6 +721,14 @@ view_scales_from_graticule <- function(graticule, scale, aesthetic,
     accept_start <- graticule[[orth_start]] < thres
     accept_end   <- graticule[[orth_end]]   < thres
   }
+  if (!any(accept_start | accept_end)) {
+    eps <- sqrt(.Machine$double.xmin)
+    subtract <- switch(position, top = , bottom = 90, 0)
+    straight <-
+      abs(graticule$angle_start - subtract) < eps &
+      abs(graticule$angle_end   - subtract) < eps
+    accept_start <- straight
+  }
 
   # Parsing the information of the `label_axes` argument:
   # should we label the meridians ("E") or parallels ("N")?

tests/testthat/test-coord_sf.R

@@ -425,3 +425,15 @@ test_that("coord_sf() can render with empty graticules", {
   p <- suppressWarnings(layer_grob(ggplot(df) + geom_sf())[[1]])
   expect_length(p$x, 1)
 })
+
+test_that("coord_sf() can calculate breaks when expansion is on", {
+  skip_if_not_installed("sf")
+  df <- sf::st_multipoint(cbind(c(-180, 180), c(-90, 90)))
+  df <- sf::st_sfc(df, crs = 4326)
+  b <- ggplot_build(ggplot(df) + geom_sf())
+
+  x <- get_guide_data(b, "x")
+  y <- get_guide_data(b, "y")
+  expect_equal(nrow(x), 5L)
+  expect_equal(nrow(y), 3L)
+})