select_helpers accept character vector?

[ruaridhw]

Possible feature request though this may contradict #49

Allow for natively passing a vector of strings to starts_with, ends_with, contains ... in order to avoid having to redefine the regex

Currently:
(1) Unwieldy manual list of single columns

select(df,
       starts_with("a"),
       starts_with("b"),
       ends_with("c"),
       ends_with("d"),
       ...)

or

(2) Redefine matching regex for each select_helper

long_list_of_select_vars <- c("a", "b", ...)
another_long_vector <- c("c", "d", ...)
select(df,
       matches(paste0("^(", paste(long_list_of_select_vars, collapse="|"), ")")),
       matches(paste0("(", paste(another_long_vector, collapse="|"), ")$")))

Request:

select(df,
       starts_with(c("a", "b")),
       ends_with(c("c", "d")),
       ...)

which would have the same behaviour as (1)

For context

[huftis]

The PR at tidyverse/dplyr#2958 (never commited) changed the semantics so that:

Selecting verbs (e.g. `select()` or verbs supporting `vars()`
selections) now treat symbols a bit differently. Symbols are only
evaluated in the data context, never in the calling context (#2904).
This means that you can no longer refer to local variables unless
you are explicitly unquoting these variables with `!!`.

Note that since last version, helper calls (like `starts_with()`)
obey the opposite behaviour and are evaluated in the calling
context, not the data context. To sum up, symbols can only refer to
data frame objects, while helpers can only refer to contextual
objects.

(Source: tidyverse/dplyr@331ed4e)

As long as it’s documented, that sounds like a reasonable behaviour, IMHO.