[ and [[ keep attributes (#275)

* [ and [[ keep attributes

* Keep pillar attribute to ensure formatting survives subsetting

* Only test pillar attribute

* Update R/make_units.R

Co-authored-by: Iñaki Ucar <iucar@fedoraproject.org>

R/conversion.R

@@ -194,12 +194,14 @@ as_difftime <- function(x) {
 
 
 #' @export
-`[.units` <- function(x, i, j, ..., drop = TRUE)
-  .as.units(NextMethod(), units(x))
+`[.units` <- function(x, i, j, ..., drop = TRUE) {
+  restore_units(NextMethod(), x)
+}
 
 #' @export
-`[[.units` <- function(x, i, j, ...)
-  .as.units(NextMethod(), units(x))
+`[[.units` <- function(x, i, j, ...) {
+  restore_units(NextMethod(), x)
+}
 
 #' @export
 as.POSIXct.units = function (x, tz = "UTC", ...) {

R/make_units.R

@@ -6,6 +6,12 @@
     structure(x, units = value, dim = dim, class = "units")
 }
 
+restore_units <- function(x, to) {
+  out <- .as.units(x, units(to))
+  attr(out, "pillar") <- attr(to, "pillar")
+  out
+}
+
 #' @name units
 #' @export
 #'

tests/testthat/test_misc.R

@@ -116,3 +116,11 @@ test_that("str works", {
     str(set_units(1/1:3, m/s))
   })
 })
+
+test_that("subsetting keeps pillar attribute (#275)", {
+  x <- set_units(1:3, m)
+  attr(x, "pillar") <- "bar"
+
+  expect_equal(attr(x[1:2], "pillar"), "bar")
+  expect_equal(attr(x[[1]], "pillar"), "bar")
+})