selects.grouped_df + non-syntactic variables

Fixes #1138

NEWS.md

@@ -1,5 +1,8 @@
 # dplyr 0.4.3.9000
 
+* `select()` works even if the grouping variable has a non-syntactic name 
+  (#1138).
+
 * In `select()`, negating a failed match (e.g. `select(mtcars, -contains("x"))`)
   returns all columns, instead of no columns (#1176)
 

R/grouped-df.r

@@ -95,7 +95,8 @@ select_.grouped_df <- function(.data, ..., .dots) {
   vars <- select_vars_(names(.data), dots)
 
   # Ensure all grouping variables are present, notifying user with a message
-  missing <- setdiff(as.character(groups(.data)), vars)
+  group_names <- vapply(groups(.data), as.character, character(1))
+  missing <- setdiff(group_names, vars)
 
   if (length(missing) > 0) {
     message("Adding missing grouping variables: ",

tests/testthat/test-select.r

@@ -24,6 +24,11 @@ test_that("grouping variables preserved with a message (#1511)", {
   expect_named(res, c("g", "x"))
 })
 
+test_that("non-syntactic grouping variable is preserved (#1138)", {
+  df <- data_frame(`a b` = 1L) %>% group_by(`a b`) %>% select()
+  expect_named(df, "a b")
+})
+
 test_that("select doesn't fail if some names missing", {
   df1 <- data.frame(x = 1:10, y = 1:10, z = 1:10)
   df2 <- setNames(df1, c("x", "y", ""))