attr_getter() uses partial matching, which is error-prone/dangerous

[huftis]

Here’s a bug/misfeature is was bitten by today. Basically, I was trying to extract the label associated with each variable in a tibble, using (bascially) map(df, attr_getter("label")).

However, for some of the variables, the value of the labels (note the s) attribute, a ‘> 1’-length vector, were extracted instead. It turned out that this happens when the label attribute is missing. The reason is partial matching on the attribute name, which unfortunately is the default in attr().

It’s to late to change the base attr() function, but partial matching is dangerous ☠️, and I see no reason that this should be the default in attr_getter() too!

To fix this, one only needs to add exact = TRUE in the call to the attr function in get_attr().

Reprex:

library(purrr)
x = c(0, 1, 1, 0)
attr(x, "labels") = c(`0` = "Female", `1` = "Male")
get_label = attr_getter("label")
get_label(x) # Expected output: NULL
#>        0        1 
#> "Female"   "Male"

[hadley]

Do you want to do a PR?

[huftis]

Sure, @hadley, I can try to create a PR.

[huftis]

I’ve now added a PR for this issue, @hadley.