Suppress default NA handling for geom_ribbon.

Fixes #1549

Author: hadley

NEWS.md

@@ -55,6 +55,9 @@
 
 * `geom_path()` knows that "solid" (not just 1) represents a solid line (#1534).
 
+* `geom_ribbon()` preserves missing values so they correctly generate a 
+  gap in the ribbon (#1549).
+
 * `geom_histgram(bins = n)` now gives a histogram with `n` bins, not `n + 1`
   (#1487).
 

R/geom-ribbon.r

@@ -65,6 +65,10 @@ GeomRibbon <- ggproto("GeomRibbon", Geom,
 
   draw_key = draw_key_polygon,
 
+  handle_na = function(data, params) {
+    data
+  },
+
   draw_group = function(data, panel_scales, coord, na.rm = FALSE) {
     if (na.rm) data <- data[stats::complete.cases(data[c("x", "ymin", "ymax")]), ]
     data <- data[order(data$group, data$x), ]

tests/testthat/test-geom-ribbon.R

@@ -0,0 +1,10 @@
+context("geom_ribbon")
+
+test_that("NAs are not dropped from the data", {
+  df <- data.frame(x = 1:5, y = c(1, 1, NA, 1, 1))
+
+  p <- ggplot(df, aes(x))+
+    geom_ribbon(aes(ymin = y - 1, ymax = y + 1))
+
+  expect_equal(layer_data(p)$ymin, c(0, 0, NA, 0, 0))
+})