Allow trailing_whitespace_linter to skip empty lines

Author: flying-sheep

R/trailing_whitespace_linter.R

@@ -1,34 +1,44 @@
 #' @describeIn linters check there are no trailing whitespace characters.
 #' @export
-trailing_whitespace_linter <- function(source_file) {
+trailing_whitespace_linter <- function(check_empty_lines = TRUE) {
+  # for backwards compatibility, check if this was called on the
+  # check_empty_lines option or directly on a source file
+  if (is.logical(check_empty_lines)) {
+    function(source_file) trailws_linter(source_file, check_empty_lines)
+  } else {  # call with old default
+    source_file <- check_empty_lines
+    trailws_linter(source_file, TRUE)
+  }
+}
+
+trailws_linter <- function(source_file, check_empty_lines) {
   res <- re_matches(source_file$lines,
     rex(capture(name = "space", some_of(" ", regex("\\t"))), or(newline, end)),
     global = TRUE,
     locations = TRUE)
 
-  lapply(seq_along(source_file$lines), function(itr) {
+  if (any(lapply(res, nrow) != 1L)) {
+    stop("invalid data: text after '\\n' found")
+  }
 
-      mapply(
-        FUN = function(start, end) {
-          if (is.na(start)) {
-            return()
-          }
-          line_number <- names(source_file$lines)[itr]
-          Lint(
-            filename = source_file$filename,
-            line_number = line_number,
-            column_number = start,
-            type = "style",
-            message = "Trailing whitespace is superfluous.",
-            line = source_file$lines[as.character(line_number)],
-            ranges = list(c(start, end)),
-            linter = "trailing_whitespace_linter"
-            )
-        },
-        start = res[[itr]]$space.start,
-        end = res[[itr]]$space.end,
-        SIMPLIFY = FALSE
-        )
-  })
+  lapply(seq_along(source_file$lines), function(idx) {
+    start <- res[[idx]]$space.start
+    end   <- res[[idx]]$space.end
 
+    skip_empty_line <- !check_empty_lines && start == 1L
+    if (is.na(start) || skip_empty_line) {
+      return()
+    }
+
+    Lint(
+      filename = source_file$filename,
+      line_number = names(source_file$lines)[[idx]],
+      column_number = start,
+      type = "style",
+      message = "Trailing whitespace is superfluous.",
+      line = source_file$lines[[idx]],
+      ranges = list(c(start, end)),
+      linter = "trailing_whitespace_linter"
+    )
+  })
 }

R/zzz.R

@@ -4,6 +4,7 @@
 #' @title linters
 #' @param source_file returned by \code{\link{get_source_expressions}}
 #' @param length the length cutoff to use for the given linter.
+#' @param check_empty_lines if \code{trailing_whitespace_linter} should consider completely empty lines.
 NULL
 
 named_list <- function(...) {
@@ -75,7 +76,7 @@ default_linters <- with_defaults(default = list(),
   multiple_dots_linter,
   object_length_linter(30),
   object_usage_linter,
-  trailing_whitespace_linter,
+  trailing_whitespace_linter(),
   trailing_blank_lines_linter,
   commented_code_linter,
 

man/linters.Rd

@@ -2,16 +2,16 @@ context("trailing_whitespace_linter")
 test_that("returns the correct linting", {
   expect_lint("blah",
     NULL,
-    trailing_whitespace_linter)
+    trailing_whitespace_linter())
 
   expect_lint("blah <- 1  ",
     c(message = rex("Trailing whitespace is superfluous."),
       column_number = 10),
-    trailing_whitespace_linter)
+    trailing_whitespace_linter())
 
   expect_lint("blah <- 1  \n'hi'",
     rex("Trailing whitespace is superfluous."),
-    trailing_whitespace_linter)
+    trailing_whitespace_linter())
 
   expect_lint("blah <- 1\n'hi'\na <- 2  ",
     list(
@@ -20,5 +20,5 @@ test_that("returns the correct linting", {
         line_number = 3
       )
     ),
-    trailing_whitespace_linter)
+    trailing_whitespace_linter())
 })