tests/testthat/test-empty_assignment_linter.R

In lintr: A 'Linter' for R Code

test_that("empty_assignment_linter skips valid usage", {
  expect_lint("x <- { 3 + 4 }", NULL, empty_assignment_linter())
  expect_lint("x <- if (x > 1) { 3 + 4 }", NULL, empty_assignment_linter())

  # also triggers assignment_linter
  expect_lint("x = { 3 + 4 }", NULL, empty_assignment_linter())
})

test_that("empty_assignment_linter blocks disallowed usages", {
  linter <- empty_assignment_linter()
  lint_msg <- rex::rex("Assign NULL explicitly or, whenever possible, allocate the empty object")

  expect_lint("xrep <- {}", lint_msg, linter)

  # assignment with equal works as well, and white space doesn't matter
  expect_lint("x = {   }", lint_msg, linter)

  # ditto right assignments
  expect_lint("{} -> x", lint_msg, linter)
  expect_lint("{} ->> x", lint_msg, linter)

  # ditto data.table-style walrus assignments
  expect_lint("x[, col := {}]", lint_msg, linter)

  # newlines also don't matter
  expect_lint("x <- {\n}", lint_msg, linter)

  # LHS of assignment doesn't matter
  expect_lint("env$obj <- {}", lint_msg, linter)
})