Gt: tidyselect-based improvements

[jthomasmock]

---

When trying to apply some type of adjustment to multiple columns, I would typically want to do:
col_1:col_n, this fails w/ vars(), which forces the user to move to naming every column. This is fine for small tables, but could be a bad UX for many col names.

reprex

library(gt)

# Fails 
gtcars %>%
  head() %>% 
  gt() %>% 
  tab_spanner(
    label = "Gas Mileage",
    columns = vars(
      mpg_c:mpg_h
    )
  )
#> Error: Can't convert a call to a string


# works
gtcars %>%
  head() %>% 
  gt() %>% 
  tab_spanner(
    label = "Gas Mileage",
    columns = vars(
      mpg_c, mpg_h
    )
  )

mfr	model	year	trim	bdy\_style	hp	hp\_rpm	trq	trq\_rpm	Gas Mileage		drivetrain	trsmn	ctry\_origin	msrp
									mpg\_c	mpg\_h
Ford	GT	2017	Base Coupe	coupe	647	6250	550	5900	11	18	rwd	7a	United States	447000
Ferrari	458 Speciale	2015	Base Coupe	coupe	597	9000	398	6000	13	17	rwd	7a	Italy	291744
Ferrari	458 Spider	2015	Base	convertible	562	9000	398	6000	13	17	rwd	7a	Italy	263553
Ferrari	458 Italia	2014	Base Coupe	coupe	562	9000	398	6000	13	17	rwd	7a	Italy	233509
Ferrari	488 GTB	2016	Base Coupe	coupe	661	8000	561	3000	15	22	rwd	7a	Italy	245400
Ferrari	California	2015	Base Convertible	convertible	553	7500	557	4750	16	23	rwd	7a	Italy	198973

^{Created on 2020-06-17 by the reprex package (v0.3.0)}

[meersel]

Please add tidy_select option when selecting column names :

Example:
columns = vars(ends_with("old"))

[rich-iannone]

This is pretty overdue. Definitely need to overhaul tidyselect support, thanks!

[rich-iannone]

Given the tidyselect improvements we made in a recent PR, @jthomasmock 's example code now works!

The revised code (sans vars()) is:

gtcars %>%
  head() %>% 
  gt() %>% 
  tab_spanner(
    label = "Gas Mileage",
    columns = mpg_c:mpg_h
  )

The table looks like this: