allow argument na.rm in median() (#483)

Fixes #442

NEWS.md

@@ -1,6 +1,8 @@
 # dbplyr (development version)
 
 * All old lazy eval shims have been removed. 
+* `median()` now takes a new argument `na.rm` for consistency with `mean()`,
+  but still does always remove any missing values (@lorenzwalthert, #483).
 
 # dbplyr 1.4.4
 

R/translate-sql-quantile.R

@@ -29,9 +29,10 @@ sql_median <- function(f,
                        style = c("infix", "ordered"),
                        window = FALSE) {
 
+  warned <- FALSE
   quantile <- sql_quantile(f, style = style, window = window)
-
-  function(x) {
+  function(x, na.rm = FALSE) {
+    warned <<- check_na_rm(f, na.rm, warned)
     quantile(x, 0.5)
   }
 }

tests/testthat/test-translate-sql-quantile.R

@@ -4,13 +4,23 @@ test_that("quantile and median don't change without warning", {
   reg <- list(
     quantile = translate_sql(quantile(x, 0.75), window = FALSE),
     quantile_win = translate_sql(quantile(x, 0.75), vars_group = "g"),
-    median = translate_sql(median(x), window = FALSE),
-    median_win = translate_sql(median(x), vars_group = "g")
+    median = translate_sql(median(x, na.rm = TRUE), window = FALSE),
+    median_win = translate_sql(median(x, na.rm = TRUE), vars_group = "g")
   )
 
   expect_known_output(print(reg), test_path("sql/backend-quantile.sql"))
 })
 
+
+test_that("median functions warn once if na.rm = FALSE", {
+  old <- set_current_con(simulate_dbi())
+  on.exit(set_current_con(old))
+
+  expect_warning(translate_sql(median("x")), "Missing values")
+  expect_warning(translate_sql(median("x")), NA)
+  expect_warning(translate_sql(median("x", na.rm = TRUE)), NA)
+})
+
 test_that("checks for invalid probs", {
   expect_error(check_probs("a"), "numeric")
   expect_error(check_probs(1:3), "single value")