format(hms()) should produce an empty character vector

[kevinushey]

> library(hms)
> format(hms())
[1] "hms()"

This was surprising to me; I think in general the contract for format() is that it produces a character vector of the same length as its input.

[krlmlr]

Thanks. Indeed, this seems true in the vctrs ecosystem (but not for data frames).

format(vctrs::new_list_of())
#> character(0)
format(vctrs::new_vctr(integer()))
#> character(0)
dput(format(data.frame()))
#> structure(list(), names = character(0), row.names = integer(0), class = "data.frame")

^{Created on 2025-01-31 with reprex v2.1.1}

Need to assess the impact on the downstream dependencies.