tests/testthat/test-scalar_in_linter.R

In lintr: A 'Linter' for R Code

test_that("scalar_in_linter skips allowed usages", {
  linter <- scalar_in_linter()

  expect_lint("x %in% y", NULL, linter)
  expect_lint("y %in% c('a', 'b')", NULL, linter)
  expect_lint("c('a', 'b') %chin% x", NULL, linter)
  expect_lint("z %in% 1:3", NULL, linter)
  # scalars on LHS are fine (often used as `"col" %in% names(DF)`)
  expect_lint("3L %in% x", NULL, linter)

  # this should be is.na(x), but it more directly uses the "always TRUE/FALSE, _not_ NA"
  #   aspect of %in%, so we delegate linting here to equals_na_linter()
  expect_lint("x %in% NA", NULL, linter)
  expect_lint("x %in% NA_character_", NULL, linter)
})

test_that("scalar_in_linter blocks simple disallowed usages", {
  linter <- scalar_in_linter()
  lint_in_msg <- rex::rex("Use == to match length-1 scalars, not %in%.")
  lint_chin_msg <- rex::rex("Use == to match length-1 scalars, not %chin%.")

  expect_lint("x %in% 1", lint_in_msg, linter)
  expect_lint("x %chin% 'a'", lint_chin_msg, linter)
})

test_that("multiple lints are generated correctly", {
  linter <- scalar_in_linter()

  expect_lint(
    trim_some('{
      x %in% 1
      y %chin% "a"
    }'),
    list("%in%", "%chin%"),
    linter
  )
})