tests/testthat/test-lazy.R

In lazyeval: Lazy (Non-Standard) Evaluation

context("lazy")


lazy_caller <- function(arg) {
  lazy(arg)
}
outer_fun <- function(arg) {
  lazy_caller(arg)
}


test_that("basic lazy() functionality works", {
  expect_equal(lazy_caller(0)$expr, 0)
  expect_equal(lazy_caller("char")$expr, "char")
  expect_equal(lazy_caller(sym)$expr, as.name("sym"))
  expect_equal(lazy_caller(call("name"))$expr, quote(call("name")))
})

test_that("lazy() works with nested promises", {
  expect_equal(outer_fun(0)$expr, 0)
  expect_equal(outer_fun("char")$expr, "char")
  expect_equal(outer_fun(sym)$expr, as.name("sym"))
  expect_equal(outer_fun(call("name"))$expr, quote(call("name")))
})

test_that("lazy() does not unpack lazily loaded objects", {
  lazy <- lazy_caller(mean)
  expect_equal(deparse(lazy$expr), "mean")

  nested_lazy <- outer_fun(mean)
  expect_equal(deparse(lazy$expr), "mean")

  outer_fun2 <- function() {
    list(
      lazy = lazy_caller(mean),
      env = environment()
    )
  }
  embedded_lazy <- outer_fun2()
  expect_identical(embedded_lazy$lazy$expr, as.name("mean"))
  expect_identical(embedded_lazy$lazy$env, embedded_lazy$env)
})

test_that("lazy() works for double-colon operator", {
  expect_error(lazy <- lazy_caller(stats::runif(10)), NA)
  expect_error(nested_lazy <- outer_fun(stats::runif(10)), NA)
})