From ab222e49b0b88bf6ef2cad5bac0fc2fbcccddfa4 Mon Sep 17 00:00:00 2001
From: DavisVaughan <davis@rstudio.com>
Date: Tue, 16 Nov 2021 15:19:31 -0500
Subject: [PATCH 1/2] Return `logical()` from `vec_equal_na(NULL)`

---
 src/equal.c                 | 4 ++++
 tests/testthat/test-equal.R | 4 ++++
 2 files changed, 8 insertions(+)

diff --git a/src/equal.c b/src/equal.c
index f4be86a68..7b0e70ee6 100644
--- a/src/equal.c
+++ b/src/equal.c
@@ -475,6 +475,10 @@ SEXP vec_equal_na(SEXP x) {
     UNPROTECT(1);
     return out;
   }
+  case vctrs_type_null: {
+    UNPROTECT(1);
+    return vctrs_shared_empty_lgl;
+  }
   case vctrs_type_scalar:    Rf_errorcall(R_NilValue, "Can't detect `NA` values in scalars with `vctrs_equal_na()`.");
   default:                   Rf_error("Unimplemented type in `vctrs_equal_na()`.");
   }
diff --git a/tests/testthat/test-equal.R b/tests/testthat/test-equal.R
index 8a22286d8..115909e06 100644
--- a/tests/testthat/test-equal.R
+++ b/tests/testthat/test-equal.R
@@ -303,6 +303,10 @@ test_that("works recursively with data frame columns", {
   expect_equal(vec_equal_na(df), c(FALSE, FALSE, FALSE, TRUE))
 })
 
+test_that("works with `NULL` input (#1494)", {
+  expect_identical(vec_equal_na(NULL), logical())
+})
+
 test_that("NA propagate symmetrically (#204)", {
   exp <- c(NA, NA)
 

From c5e1a098ea5a7de45d2fe30e9caf3505c4ce175c Mon Sep 17 00:00:00 2001
From: DavisVaughan <davis@rstudio.com>
Date: Tue, 16 Nov 2021 15:19:39 -0500
Subject: [PATCH 2/2] NEWS bullet

---
 NEWS.md | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/NEWS.md b/NEWS.md
index f386b4411..a20df231e 100644
--- a/NEWS.md
+++ b/NEWS.md
@@ -1,5 +1,7 @@
 # vctrs (development version)
 
+* `vec_equal_na(NULL)` now returns `logical(0)` rather than erroring (#1494).
+
 * `vec_as_location(missing = "error")` now fails with `NA` and `NA_character_`
   in addition to `NA_integer_` (#1420, @krlmlr).