Improve errors when a non-vector is passed to expect_vector.

The `expect_vector` function delegates most of its logic to
`vctrs::vec_assert`, which can throw one of two errors,
`vctrs_error_assert` and `vctrs_error_scalar_type`.

Only the former one was being handled, not the latter. This doesn't
affect the behaviour of tests much, but it produces sub-par error
messages and causes failing tests to terminate immediately rather than
recording the error and continuing like other assertions do.

Author: plietar

R/expect-vector.R

@@ -23,6 +23,9 @@ expect_vector <- function(object, ptype = NULL, size = NULL) {
   message <- NULL
   tryCatch(
     vctrs::vec_assert(act$val, ptype = ptype, size = size, arg = act$lab),
+    vctrs_error_scalar_type = function(e) {
+      message <<- e$message
+    },
     vctrs_error_assert = function(e) {
       message <<- e$message
     }

tests/testthat/test-expect-vector.R

@@ -3,6 +3,7 @@ test_that("basic properties upheld", {
 
   expect_success(expect_vector(1:10, size = 10))
   expect_failure(expect_vector(1:10, size = 5))
+  expect_failure(expect_vector(NULL))
 })
 
 test_that("expect_vector validates its inputs", {