Ensure count() adds grouping vars

Fixes tidyverse#1703

NEWS.md

@@ -1,5 +1,8 @@
 # dplyr 0.4.3.9000
 
+* `count()` now adds additional grouping variables, rather than overriding
+  existing (#1703).
+
 * `pmin()` and `pmax()` are translated to SQL `MIN()` and `MAX()` (#1711).
 
 * `case_when()` is a general vectorised if + else if (#631).

R/tally.R

@@ -86,6 +86,6 @@ count <- function(x, ..., wt = NULL, sort = FALSE) {
 #' @export
 #' @rdname tally
 count_ <- function(x, vars, wt = NULL, sort = FALSE) {
-  grouped <- group_by_(x, .dots = vars)
+  grouped <- group_by_(x, .dots = vars, add = TRUE)
   tally_(grouped, wt = wt, sort = sort)
 }

tests/testthat/test-count.r

@@ -11,6 +11,14 @@ test_that("can count variable called n", {
   expect_equal(out$nn, c(3, 2))
 })
 
+test_that("grouped count includes group", {
+  df <- data.frame(g = c(1, 2, 2, 2))
+
+  res <- df %>% group_by(g) %>% count()
+  expect_equal(names(res), c("g", "n"))
+  expect_equal(res$n, c(1, 3))
+})
+
 # n_distinct --------------------------------------------------------------
 
 test_that("count_distinct gives the correct results on iris", {