This looks good. It may be a function that predates me, and the use if NA here is a little non-standard (maybe check for missing() or empty string is cleaner) but changing it now and changing the interface is not great either.

missing has it issues, so I tend to prefer having a default over using missing; Seurat uses NULL since rlang has %||% to check for it, but I think NA works well enough here. Plus, in the help page, the default is NA_character_ which indicates that config should be a character

Let's table whether rlang is authorative for another day but I guess I meant to approve and comment and just commented. Correcting that now.

The other reason that issue went undetected is that most uses of config use this pattern for one or more settings

cfg <- tiledb_config()
cfg["vfs.s3.region"] <- "us-west-1"
ctx <- tiledb_ctx(cfg)

and the more compact form of the named charecter vector which, as you correctly identified could be longer than length one, is not use much (but even more convenient).

Oh, one more thing: can you add a line to NEWS.md with the PR number? I found adding [ci_skip] to the commit makes it a little lighter on non-code commits.

And then as it is approved feel free to squash-merge.