Coerce n to integer in lead too (#1383)

Fixes r-dbi/bigrquery#543

NEWS.md

@@ -1,13 +1,11 @@
 # dbplyr (development version)
 
-## Minor improvements and bug fixes
+* `lead()` translation coerces `n` to an integer.
 
 * `sql_translator()` now checks for duplicated definitions (@krlmlr, #1374).
 
 * `reframe()` now gives an informative error that it isn't supported (#1148).
 
-## Backend specific improvements
-
 * MySQL/MariaDB:
   * Fix translation of `as.integer()` for MySQL (@krlmlr, #1375).
   * New `simulate_mariadb()` (@krlmlr, #1375).

R/backend-.R

@@ -446,7 +446,7 @@ base_win <- sql_translator(
 
   lead = function(x, n = 1L, default = NA, order_by = NULL) {
     win_over(
-      sql_expr(LEAD(!!x, !!n, !!default)),
+      sql_expr(LEAD(!!x, !!as.integer(n), !!default)),
       win_current_group(),
       order_by %||% win_current_order(),
       win_current_frame()

R/backend-redshift.R

@@ -81,7 +81,7 @@ sql_translation.RedshiftConnection <- function(con) {
       # https://docs.aws.amazon.com/redshift/latest/dg/r_WF_LEAD.html
       lead = function(x, n = 1L, order_by = NULL) {
         win_over(
-          sql_expr(LEAD(!!x, !!n)),
+          sql_expr(LEAD(!!x, !!as.integer(n))),
           win_current_group(),
           order_by %||% win_current_order(),
           win_current_frame()

tests/testthat/test-backend-.R

@@ -78,6 +78,15 @@ test_that("can translate subsetting", {
 })
 
 
+# window ------------------------------------------------------------------
+
+test_that("lead and lag translate n to integers", {
+  local_con(simulate_dbi())
+
+  expect_equal(test_translate_sql(lead(x, 1)), sql("LEAD(`x`, 1, NULL) OVER ()"))
+  expect_equal(test_translate_sql(lag(x, 1)), sql("LAG(`x`, 1, NULL) OVER ()"))
+})
+
 # strings -----------------------------------------------------------------
 
 test_that("can translate case insensitive like", {