Do not treat Rmd files without code as being all code

Fixes #370

NEWS.md

@@ -1,4 +1,5 @@
 # lintr 1.0.3.9000 # 
+* R Markdown files that do not contain chunks are no longer treated as code (#370).
 * `open_curly_linter()` and `closed_curly_linter()` now do not lint double curly syntax (#388)
 * `open_curly_linter()` now allows comments after the curly braces (#188)
 * `lint_package()` now excludes `R/RcppExports.R` by default (#282)

R/extract.R

@@ -14,7 +14,7 @@ extract_r_source <- function(filename, lines) {
 
   # no chunks found, so just return the lines
   if (length(starts) == 0 || length(ends) == 0) {
-    return(lines)
+    return(character())
   }
 
   if (length(starts) != length(ends)) {

tests/testthat/test-knitr_formats.R

@@ -86,9 +86,7 @@ test_that("it does _not_ handle brew", {
 })
 
 test_that("it does _not_ error with inline \\Sexpr", {
-  expect_lint("#' text \\Sexpr{1 + 1} more text\n",
-    checks = list(
-      rex("Trailing blank lines are superfluous.")
-    ),
+  expect_lint("#' text \\Sexpr{1 + 1} more text",
+    NULL,
     default_linters)
 })