exclude %<>% from one_call_pipe_linter (#2331)

NEWS.md

@@ -39,6 +39,7 @@
 * `nested_pipe_linter()` for discouraging pipes within pipes, e.g. `df1 %>% inner_join(df2 %>% select(a, b))` (part of #884, @MichaelChirico).
 * `nrow_subset_linter()` for discouraging usage like `nrow(subset(x, conditions))` in favor of something like `with(x, sum(conditions))` which doesn't require a full subset of `x` (part of #884, @MichaelChirico).
 * `pipe_return_linter()` for discouraging usage of `return()` inside a {magrittr} pipeline (part of #884, @MichaelChirico).
+* `one_call_pipe_linter()` for discouraging one-step pipelines like `x |> as.character()` (#2330 and part of #884, @MichaelChirico).
 
 ### Lint accuracy fixes: removing false positives
 

R/one_call_pipe_linter.R

@@ -31,13 +31,20 @@
 #'   linters = one_call_pipe_linter()
 #' )
 #'
+#' # assignment pipe is exempted
+#' lint(
+#'   text = "DF %<>% mutate(a = 2)",
+#'   linters = one_call_pipe_linter()
+#' )
+#'
 #' @evalRd rd_tags("one_call_pipe_linter")
 #' @seealso
 #' - [linters] for a complete list of linters available in lintr.
 #' - <https://style.tidyverse.org/pipes.html#short-pipes>
 #' @export
 one_call_pipe_linter <- function() {
-  pipes_cond <- xp_text_in_table(magrittr_pipes)
+  # exception for assignment pipe per #2330
+  pipes_cond <- xp_text_in_table(setdiff(magrittr_pipes, "%<>%"))
 
   # preceding-sibling::SPECIAL: if there are ever two pipes, don't lint
   # OP-LEFT-BRACKET/LBB: accept DT[...] %>% .[...] as a two-call pipe,

tests/testthat/test-one_call_pipe_linter.R

@@ -7,6 +7,9 @@ test_that("one_call_pipe_linter skips allowed usages", {
   expect_lint("foo(x) %>% bar()", NULL, linter)
   # both calls in second step --> OK
   expect_lint("x %>% foo(bar(.))", NULL, linter)
+
+  # assignment pipe is exempted
+  expect_lint("x %<>% as.character()", NULL, linter)
 })
 
 test_that("one_call_pipe_linter blocks simple disallowed usages", {
@@ -41,20 +44,13 @@ test_that("one_call_pipe_linter skips data.table chains", {
 
 test_that("one_call_pipe_linter treats all pipes equally", {
   linter <- one_call_pipe_linter()
+  lint_msg_part <- "Expressions with only a single call shouldn't use pipe "
 
   expect_lint("foo %>% bar() %$% col", NULL, linter)
+  expect_lint("x %T>% foo()", rex::rex(lint_msg_part, "%T>%."), linter)
+  expect_lint("x %$%\n  foo", rex::rex(lint_msg_part, "%$%."), linter)
   expect_lint(
-    "x %T>% foo()",
-    rex::rex("Expressions with only a single call shouldn't use pipe %T>%."),
-    linter
-  )
-  expect_lint(
-    "x %$%\n  foo()",
-    rex::rex("Expressions with only a single call shouldn't use pipe %$%."),
-    linter
-  )
-  expect_lint(
-    'data %>% filter(type == "console") %$% obscured_gaia_id %>% unique()',
+    'data %>% filter(type == "console") %$% obscured_id %>% unique()',
     NULL,
     linter
   )
@@ -64,7 +60,7 @@ test_that("multiple lints are generated correctly", {
   expect_lint(
     trim_some("{
       a %>% b()
-      c %$% d()
+      c %$% d
       e %T>%
         f()
     }"),