Add .negate to filter_on (#6)

NEWS.md

@@ -4,6 +4,7 @@
 - `transmute` is no longer an alias for `select`. This is to make the latter more flexible in some
   bare selection cases (like combining several `tidyselect` calls), and leave the former more simple
   and preferable for actual transmutation cases.
+- `filter_on` gains a `.negate` parameter.
 
 # table.express 0.1.1
 

R/VERBS-filter_on.R

@@ -4,11 +4,14 @@
 #'
 #' @export
 #' @importFrom rlang abort
+#' @importFrom rlang expr
 #'
 #' @template data-arg
 #' @param ... Key-value pairs, see details.
 #' @param nomatch See [data.table::data.table].
 #' @param mult See [data.table::data.table].
+#' @param .negate Whether to negate the expression and search only for rows that don't contain the
+#'   given values.
 #' @template chain-arg
 #'
 #' @details
@@ -30,7 +33,7 @@
 #'     start_expr %>%
 #'     filter_on(cyl = 4, gear = 5)
 #'
-filter_on <- function(.data, ..., nomatch = getOption("datatable.nomatch"), mult = "all",
+filter_on <- function(.data, ..., nomatch = getOption("datatable.nomatch"), mult = "all", .negate = FALSE,
                       .chain = getOption("table.express.chain", TRUE))
 {
     key_value <- parse_dots(FALSE, ...)
@@ -41,7 +44,12 @@ filter_on <- function(.data, ..., nomatch = getOption("datatable.nomatch"), mult
         rlang::abort("All arguments in '...' must be named.")
     }
 
-    ans <- where(.data, list(!!!values), .parse = FALSE, .chain = .chain) %>%
+    clause <- rlang::expr(list(!!!values))
+    if (.negate) {
+        clause <- rlang::expr(`!`(`!!`(clause)))
+    }
+
+    ans <- .data$set_where(clause, .chain) %>%
         frame_append(on = !!keys, .parse = FALSE)
 
     if (!missing(nomatch)) {

inst/NEWS.md

@@ -4,3 +4,4 @@
 - `transmute` is no longer an alias for `select`. This is to make the latter more flexible in some
   bare selection cases (like combining several `tidyselect` calls), and leave the former more simple
   and preferable for actual transmutation cases.
+- `filter_on` gains a `.negate` parameter.

tests/testthat/unit/test-filter_on.R

@@ -24,6 +24,12 @@ test_that("The filter_on verb works as expected.", {
     expect_identical(nrow(ans), 0L)
 })
 
+test_that("The filter_on semantics can be negated.", {
+    expected <- DT[!list(0), on = "am"]
+    ans <- DT %>% start_expr %>% filter_on(am = 0, .negate = TRUE) %>% end_expr
+    expect_identical(ans, expected)
+})
+
 test_that("The filter_on verb works for several values per key.", {
     expected <- state[.(c("South", "West"), c("South Atlantic", "Pacific"))]