error on more than 1e6 bins (#3081)

Author: thomasp85

NEWS.md

@@ -44,6 +44,9 @@
 * `coord_sf()`, `coord_map()`, and `coord_polar()` now squash `-Inf` and `Inf`
   into the min and max of the plot (@yutannihilation, #2972).
 
+* `stat_bin()` will now error when the number of bins exceeds 1e6 to avoid 
+  accidentally freezing the user session (@thomasp85).
+
 # ggplot2 3.1.0
 
 ## Breaking changes

R/bin.R

@@ -87,6 +87,10 @@ bin_breaks_width <- function(x_range, width = NULL, center = NULL,
   max_x <- x_range[2] + (1 - 1e-08) * width
   breaks <- seq(origin, max_x, width)
 
+  if (length(breaks) > 1e6) {
+    stop("The number of histogram bins must be less than 1,000,000.\nDid you make `binwidth` too small?", call. = FALSE)
+  }
+
   bin_breaks(breaks, closed = closed)
 }
 

tests/testthat/test-stat-bin.R

@@ -124,6 +124,10 @@ test_that("weights are added", {
   expect_equal(out$count, df$y)
 })
 
+test_that("bin errors at high bin counts", {
+  expect_error(bin_breaks_width(c(1, 2e6), 1), "The number of histogram bins")
+})
+
 # stat_count --------------------------------------------------------------
 
 test_that("stat_count throws error when y aesthetic present", {