support for # nolint next

NEWS.md

@@ -7,6 +7,7 @@
 
 ## New and improved features
 
+* New exclusion sentinel `# nolint next` to signify the next line should skip linting (#1791, @MichaelChirico). The usual rules apply for excluding specific linters, e.g. `# nolint next: assignment_linter.`. The exact string used to match a subsequent-line exclusion is controlled by the `exclude_next` config entry or R option `"lintr.exclude_next"`.
 * Linters with logic around the magrittr pipe `%>%` consistently apply it to the other pipes `%!>%`, `%T>%`, `%<>%` (and possibly `%$%`) where appropriate (#2008, @MichaelChirico).
   + `brace_linter()`
   + `pipe_call_linter()`

R/exclude.R

@@ -82,17 +82,20 @@ line_info <- function(line_numbers, type = c("start", "end")) {
 #' read a source file and parse all the excluded lines from it
 #'
 #' @param file R source file
-#' @param exclude regular expression used to mark lines to exclude
-#' @param exclude_start regular expression used to mark the start of an excluded range
-#' @param exclude_end regular expression used to mark the end of an excluded range
-#' @param exclude_linter regular expression used to capture a list of to-be-excluded linters immediately following a
+#' @param exclude Regular expression used to mark lines to exclude.
+#' @param exclude_next Regular expression used to mark lines immediately preceding excluded lines.
+#' @param exclude_start Regular expression used to mark the start of an excluded range.
+#' @param exclude_end Regular expression used to mark the end of an excluded range.
+#' @param exclude_linter Regular expression used to capture a list of to-be-excluded linters immediately following a
 #' `exclude` or `exclude_start` marker.
-#' @param exclude_linter_sep regular expression used to split a linter list into individual linter names for exclusion.
-#' @param lines a character vector of the content lines of `file`
-#' @param linter_names Names of active linters
+#' @param exclude_linter_sep Regular expression used to split a linter list into individual linter names for exclusion.
+#' @param lines A character vector of the content lines of `file`.
+#' @param linter_names Names of active linters.
 #'
 #' @return A possibly named list of excluded lines, possibly for specific linters.
-parse_exclusions <- function(file, exclude = settings$exclude,
+parse_exclusions <- function(file,
+                             exclude = settings$exclude,
+                             exclude_next = settings$exclude_next,
                              exclude_start = settings$exclude_start,
                              exclude_end = settings$exclude_end,
                              exclude_linter = settings$exclude_linter,
@@ -131,22 +134,34 @@ parse_exclusions <- function(file, exclude = settings$exclude,
     }
   }
 
+  next_locations <- re_matches(lines, exclude_next, locations = TRUE)[, "end"] + 1L
+  nexts <- which(!is.na(next_locations))
+
   nolint_locations <- re_matches(lines, exclude, locations = TRUE)[, "end"] + 1L
   nolints <- which(!is.na(nolint_locations))
-  # Disregard nolint tags if they also match nolint start / end
-  nolints <- setdiff(nolints, c(starts, ends))
 
-  for (i in seq_along(nolints)) {
-    linters_string <- substring(lines[nolints[i]], nolint_locations[nolints[i]])
-    linters_string <- re_matches(linters_string, exclude_linter)[, 1L]
-    exclusions <- add_exclusions(exclusions, nolints[i], linters_string, exclude_linter_sep, linter_names)
+  # Disregard nolint tags if they also match nolint next / start / end
+  nolints <- setdiff(nolints, c(nexts, starts, ends))
+
+  for (nolint in nolints) {
+    linters_string <- get_linters_string(lines[nolint], nolint_locations[nolint], exclude_linter)
+    exclusions <- add_exclusions(exclusions, nolint, linters_string, exclude_linter_sep, linter_names)
+  }
+  for (nextt in nexts) {
+    linters_string <- get_linters_string(lines[nextt], next_locations[nextt], exclude_linter)
+    exclusions <- add_exclusions(exclusions, nextt + 1L, linters_string, exclude_linter_sep, linter_names)
   }
 
   exclusions[] <- lapply(exclusions, function(lines) sort(unique(lines)))
 
   exclusions
 }
 
+get_linters_string <- function(line, loc, exclude_linter) {
+  linters_string <- substring(line, loc)
+  re_matches(linters_string, exclude_linter)[, 1L]
+}
+
 add_excluded_lines <- function(exclusions, excluded_lines, excluded_linters) {
   for (linter in excluded_linters) {
     if (linter %in% names2(exclusions)) {

R/zzz.R

@@ -299,6 +299,7 @@ settings <- NULL
     linters = default_linters,
     encoding = "UTF-8",
     exclude = rex("#", any_spaces, "nolint"),
+    exclude_next = rex("#", any_spaces, "nolint next"),
     exclude_start = rex("#", any_spaces, "nolint start"),
     exclude_end = rex("#", any_spaces, "nolint end"),
     exclude_linter = rex(

tests/testthat/test-exclusions.R

@@ -152,3 +152,59 @@ test_that("#1442: is_excluded_files works if no global exclusions are specified"
   )
   expect_length(lint_dir(tmp), 3L)
 })
+
+test_that("next-line exclusion works", {
+  withr::local_options(
+    lintr.exclude = "# NL",
+    lintr.exclude_next = "# NLN",
+    lintr.exlcude_linter = default_settings$exclude_linter
+  )
+
+  linter <- assignment_linter()
+
+  # blanket exclusion works
+  expect_lint(
+    trim_some("
+      # NLN
+      x = 1
+    "),
+    NULL,
+    linter
+  )
+
+  # specific exclusion works
+  expect_lint(
+    trim_some("
+      # NLN: assignment_linter.
+      x = 1
+    "),
+    NULL,
+    linter
+  )
+  expect_lint(
+    trim_some("
+      # NLN: assignment.
+      x = 1
+    "),
+    NULL,
+    linter
+  )
+  expect_lint(
+    trim_some("
+      # NLN: line_length_linter.
+      x = 1
+    "),
+    rex::rex("Use <-, not =, for assignment."),
+    list(linter, line_length_linter())
+  )
+
+  # interaction with plain nolint
+  expect_lint(
+    trim_some("
+      x = 1 # NLN: assignment_linter.
+      x = 2
+    "),
+    list(rex::rex("Use <-, not =, for assignment."), line_number = 1L),
+    linter
+  )
+})