Block unreachable code and comments following return statements

Code after e.g. a return() or stop() or in deterministically false conditional loops like if (FALSE) can't be reached; typically this is vestigial code left after refactoring or sandboxing code, which is fine for exploration, but shouldn't ultimately be checked in. Comments meant for posterity should be placed before the final return().

Usage

unreachable_code_linter()

See also

linters for a complete list of linters available in lintr.

Tags

best_practices, readability

Examples

# will produce lints
code_lines <- "f <- function() {\n  return(1 + 1)\n  2 + 2\n}"
writeLines(code_lines)
#> f <- function() {
#>   return(1 + 1)
#>   2 + 2
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)
#> ::warning file=<text>,line=3,col=3::file=<text>,line=3,col=3,[unreachable_code_linter] Code and comments coming after a return() or stop() should be removed.

code_lines <- "f <- if (FALSE) {\n 2 + 2\n}"
writeLines(code_lines)
#> f <- if (FALSE) {
#>  2 + 2
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)
#> ::warning file=<text>,line=2,col=2::file=<text>,line=2,col=2,[unreachable_code_linter] Code inside a conditional loop with a deterministically false condition should be removed.

code_lines <- "f <- while (FALSE) {\n 2 + 2\n}"
writeLines(code_lines)
#> f <- while (FALSE) {
#>  2 + 2
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)
#> ::warning file=<text>,line=2,col=2::file=<text>,line=2,col=2,[unreachable_code_linter] Code inside a conditional loop with a deterministically false condition should be removed.

# okay
code_lines <- "f <- function() {\n  return(1 + 1)\n}"
writeLines(code_lines)
#> f <- function() {
#>   return(1 + 1)
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)

code_lines <- "f <- if (foo) {\n 2 + 2\n}"
writeLines(code_lines)
#> f <- if (foo) {
#>  2 + 2
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)

code_lines <- "f <- while (foo) {\n 2 + 2\n}"
writeLines(code_lines)
#> f <- while (foo) {
#>  2 + 2
#> }
lint(
  text = code_lines,
  linters = unreachable_code_linter()
)