Remove <<- from assignment_linter defaults

NEWS.md

@@ -3,6 +3,7 @@
 ## Deprecations & breaking changes
 
 * Six linters fully deprecated in the previous release are now removed: `consecutive_stopifnot_linter()`, `extraction_operator_linter()`, `no_tab_linter()`, `single_quotes_linter()`, `unnecessary_nested_if_linter()`, and `unneeded_concatenation_linter()`.
+* `assignment_linter()` only allows `<-` by default, i.e., `<<-` is now excluded (consistent with the defaults for `undesirable_operator_linter()`; #2717, @MichaelChirico).
 * Arguments `allow_cascading_assign=`, `allow_right_assign=`, and `allow_pipe_assign=` to `assignment_linter()` are now removed. Use `operator=` instead.
 * Argument `interpret_glue` to `object_usage_linter()`, marked deprecated in the previous release, is now defunct. Use `interpret_extensions=` instead; see the 3.3.0-1 release notes and `?object_usage_linter` for more.
 

R/assignment_linter.R

@@ -2,9 +2,9 @@
 #'
 #' Check that the specified operator is used for assignment.
 #'
-#' @param operator Character vector of valid assignment operators. Defaults to allowing `<-` and `<<-`; other valid
-#'   options are `=`, `->`, `->>`, `%<>%`; use `"any"` to denote "allow all operators", in which case this linter only
-#'   considers `allow_trailing` for generating lints.
+#' @param operator Character vector of valid assignment operators. Defaults to allowing only `<-`; other valid
+#'   options are `=`, `<<-`, `->`, `->>`, `%<>%`; use `"any"` to denote "allow all operators", in which case
+#    this linter only considers `allow_trailing` for generating lints.
 #' @param allow_trailing Logical, default `TRUE`. If `FALSE` then assignments aren't allowed at end of lines.
 #'
 #' @examples
@@ -14,7 +14,7 @@
 #'   linters = assignment_linter()
 #' )
 #'
-#' code_lines <- "1 -> x\n2 ->> y"
+#' code_lines <- "1 -> x\n2 ->> y\nz <<- 3"
 #' writeLines(code_lines)
 #' lint(
 #'   text = code_lines,
@@ -37,7 +37,7 @@
 #'   linters = assignment_linter()
 #' )
 #'
-#' code_lines <- "x <- 1\ny <<- 2"
+#' code_lines <- "x <- 1\ny <- 2\nz <- 3"
 #' writeLines(code_lines)
 #' lint(
 #'   text = code_lines,
@@ -79,7 +79,7 @@
 #' - <https://style.tidyverse.org/syntax.html#assignment-1>
 #' - <https://style.tidyverse.org/pipes.html#assignment-2>
 #' @export
-assignment_linter <- function(operator = c("<-", "<<-"),
+assignment_linter <- function(operator = "<-",
                               allow_trailing = TRUE) {
   all_operators <- c("<-", "=", "->", "<<-", "->>", "%<>%")
   if ("any" %in% operator) {

tests/testthat/test-assignment_linter.R

@@ -10,7 +10,7 @@ test_that("assignment_linter skips allowed usages", {
 
 test_that("assignment_linter blocks disallowed usages", {
   linter <- assignment_linter()
-  lint_msg <- rex::rex("Use one of <-, <<- for assignment, not =.")
+  lint_msg <- rex::rex("Use <- for assignment, not =.")
 
   expect_lint("blah=1", lint_msg, linter)
   expect_lint("blah = 1", lint_msg, linter)
@@ -32,16 +32,16 @@ test_that("arguments handle <<- and ->/->> correctly", {
   linter_yes_right <- assignment_linter(operator = c("->", "->>"))
   lint_msg_right <- rex::rex("Replace ->> by assigning to a specific environment")
 
-  expect_lint("1 -> blah", rex::rex("Use one of <-, <<- for assignment, not ->."), linter)
+  expect_lint("1 -> blah", rex::rex("Use <- for assignment, not ->."), linter)
   expect_lint("1 ->> blah", lint_msg_right, assignment_linter(operator = "<-"))
 
-  # <<- is only blocked optionally
-  expect_no_lint("1 <<- blah", linter)
+  # <<- can be unblocked optionally
   expect_lint(
     "1 <<- blah",
     rex::rex("Replace <<- by assigning to a specific environment"),
-    assignment_linter(operator = "<-")
+    linter
   )
+  expect_no_lint("1 <<- blah", assignment_linter(operator = "<<-"))
 
   # blocking -> can be disabled
   expect_no_lint("1 -> blah", linter_yes_right)
@@ -85,10 +85,10 @@ test_that("arguments handle trailing assignment operators correctly", {
 
   expect_lint(
     trim_some("
-      x <<-
+      x <-
         y
     "),
-    rex::rex("<<- should not be trailing"),
+    rex::rex("<- should not be trailing"),
     linter_no_trailing
   )
   expect_lint(
@@ -127,11 +127,11 @@ test_that("arguments handle trailing assignment operators correctly", {
       arrange(-value) ->
       is_long
   ")
-  expect_lint(pipe_right_string, rex::rex("Use one of <-, <<- for assignment, not ->"), linter_default)
+  expect_lint(pipe_right_string, rex::rex("Use <- for assignment, not ->"), linter_default)
   expect_lint(
     pipe_right_string,
     list(
-      rex::rex("Use one of <-, <<- for assignment, not ->"),
+      rex::rex("Use <- for assignment, not ->"),
       rex::rex("Assignment -> should not be trailing")
     ),
     linter_no_trailing
@@ -150,7 +150,7 @@ test_that("arguments handle trailing assignment operators correctly", {
         54
     "),
     list(
-      list(message = "Use one of <-, <<- for assignment, not =.", line_number = 1L, column_number = 6L),
+      list(message = "Use <- for assignment, not =.", line_number = 1L, column_number = 6L),
       list(message = "Assignment = should not be trailing at the end of a line", line_number = 1L, column_number = 6L),
       list(message = "Assignment <- should not be trailing at the end of a line", line_number = 3L, column_number = 6L)
     ),

tests/testthat/test-exclusions.R

@@ -206,7 +206,7 @@ test_that("next-line exclusion works", { # nofuzz
       # NLN: line_length_linter.
       x = 1
     "),
-    rex::rex("Use one of <-, <<- for assignment, not =."),
+    rex::rex("Use <- for assignment, not =."),
     list(linter, line_length_linter())
   )
 
@@ -216,7 +216,7 @@ test_that("next-line exclusion works", { # nofuzz
       x = 1 # NLN: assignment_linter.
       x = 2
     "),
-    list(rex::rex("Use one of <-, <<- for assignment, not =."), line_number = 1L),
+    list(rex::rex("Use <- for assignment, not =."), line_number = 1L),
     linter
   )
 })

tests/testthat/test-expect_lint.R

@@ -4,7 +4,7 @@
 
 # fuzzer disable: assignment
 linter <- assignment_linter()
-lint_msg <- "Use one of <-, <<- for assignment, not ="
+lint_msg <- "Use <- for assignment, not ="
 
 test_that("no checks", {
   expect_success(expect_no_lint("a", linter))

tests/testthat/test-knitr_extended_formats.R

@@ -4,7 +4,7 @@ test_that("marginfigure engine from tufte package doesn't cause problems", {
 
   expect_lint(
     file = test_path("knitr_extended_formats", "tufte.Rmd"),
-    checks = list(rex::rex("Use one of <-, <<- for assignment, not =."), line_number = 11L),
+    checks = list(rex::rex("Use <- for assignment, not =."), line_number = 11L),
     default_linters,
     parse_settings = FALSE
   )
@@ -16,7 +16,7 @@ test_that("engines from bookdown package cause no problems", {
 
   expect_lint(
     file = test_path("knitr_extended_formats", "bookdown.Rmd"),
-    checks = list(rex::rex("Use one of <-, <<- for assignment, not =."), line_number = 14L),
+    checks = list(rex::rex("Use <- for assignment, not =."), line_number = 14L),
     default_linters,
     parse_settings = FALSE
   )

tests/testthat/test-knitr_formats.R

@@ -1,5 +1,5 @@
 regexes <- list(
-  assign = rex::rex("Use one of <-, <<- for assignment, not =."),
+  assign = rex::rex("Use <- for assignment, not =."),
   local_var = rex::rex("local variable"),
   quotes = rex::rex("Only use double-quotes."),
   trailing = rex::rex("Remove trailing blank lines."),