breaks_pretty() will return zero-range limit (#455)

NEWS.md

@@ -1,5 +1,6 @@
 # scales (development version)
 
+* `breaks_pretty()` will return the input limit when it has no range (#446)
 * `transform_exp()` now has more sensible breaks, available in `breaks_exp()` 
   (@teunbrand, #405).
 * The scales package now keeps track of known palettes. These can be retrieved

R/breaks.R

@@ -122,6 +122,9 @@ breaks_pretty <- function(n = 5, ...) {
   force_all(n, ...)
   n_default <- n
   function(x, n = n_default) {
+    if (zero_range(as.numeric(x))) {
+      return(x[1])
+    }
     breaks <- pretty(x, n, ...)
     names(breaks) <- attr(breaks, "labels")
     breaks

tests/testthat/test-breaks.R

@@ -31,8 +31,11 @@ test_that("breaks_pretty() arguments are forcely evaluated on each call #81", {
   expect_equal(subfun2(1), subfuns[[2]](1))
 })
 
-test_that("exponential breaks give sensible values", {
+test_that("breaks_pretty() returns input when given zero-width range (#446)", {
+  expect_equal(breaks_pretty()(c(1, 1)), 1)
+})
 
+test_that("exponential breaks give sensible values", {
   x <- breaks_exp()(c(0, 2))
   expect_equal(x, c(0, 0.5, 1, 1.5, 2))