Feature request: support for .data pronoun

[karldw]

Thanks for the great package!

I'm wondering if you'd consider adding support for the .data and .env pronouns from the tidyverse's new tidyeval framework. (.data says "look in the dataframe for the column" while .env says something like "look in the environment for the value")

See the dplyr programming vignette has some background.) I think the rlang::eval_tidy function will be key here.

Here's a demo:

library(rlang)
library(assertr)

mtcars %>% verify(mpg > 30)  # verify works!
#> verification [mpg > 30] failed! (28 failures)

mgp <- 40
mtcars %>% verify(mgp > 30)  # fat fingers :(
# No error because mgp exists elsewhere

# I'd like to write:
mtcars %>% verify(.data$mpg > 30)
# and 
mtcars %>% verify(.data$mpg > .env$mgp)


# How it works in dplyr:
mtcars %>% dplyr::mutate(x = mgp)  # no error, but mgp always 40

# but if we're careful, we get an error
mtcars %>% dplyr::mutate(x = .data$mgp)
#> Error in mutate_impl(.data, dots) : 
#>  Evaluation error: Column `mgp`: not found in data.

[karldw]

Hmm, it seems that .env might not be helpful because of the way %>% works. See r-lib/rlang#339 for details.
I think .data might still be useful.

[tonyfischetti]

Haha, I'll have to read the vignette you posted.
I'll check back in when I've read it

Thanks for the suggestion :)

[tonyfischetti]

Hi!
I'd definitely consider adding this. I see you're a contributor to rlang, would you like to submit a pull request? I feel like I don't understand rlang nearly as well as you.

[karldw]

Sure! It will be a bit before I'm able to write the PR, but it's on my list.

[tonyfischetti]

Great! Thank you very much :)