Improve error message with missing arguments

[lionel-]

expect_identical("foo")
#> Error in eval_bare(get_expr(quo), get_env(quo)) (from eval.R#97) : object '' not found

[jimhester]

Any thoughts on a good way to handle this for all expectations?

I can do something like this, but the error message then is not much better.

diff --git a/R/expectation.R b/R/expectation.R
index 6dfd504..2f248c0 100644
--- a/R/expectation.R
+++ b/R/expectation.R
@@ -85,7 +85,9 @@ is.expectation <- function(x) inherits(x, "expectation")
 #' # variable name
 #' show_failure(expect_equal(f(!!i), !!(i * 10)))
 quasi_label <- function(quo, label = NULL) {
-  force(quo)
+  if (quo_is_missing(quo)) {
+    stop("`quo` is missing", call. = FALSE)
+  }

   list(
     val = eval_bare(get_expr(quo), get_env(quo)),

expect_identical("foo")
#> Error: quo is missing

Ideally this would be

`expected` is missing

I could hoist the quo_is_missing() check up to the expect_identical() body I guess, but then I would need to modify all of the other expectations in a similar way, which seems painful.

[lionel-]

Unfortunately I think there's no great way around this other than adding an explicit argument to quasi_label() to pass the argument name.

[lionel-]

Something like "Missing argument in expectation" would already be much better though.