Using pre-existing character vectors in quasiquotation of an expression with rlang

Sometimes when working with dplyr one has a character vector of column names that's to be used to operate on data, for instance:

 cols_of_interest <- c("Petal.Width", "Petal.Length")

In dplyr 0.5.0 and earlier, the recommended approach to this problem was to use the verb_ underscore construct as follows:

library("tidyverse")
my_cols <- c("Petal.Width", "Petal.Length")
iris %>%
  select_(.dots = my_cols)

The verb_ functions are now deprecated in favour of the new tidy evaluation framework (dplyr.tidyverse.org/articles/programming.html) introduced by the rlang library.

As of dplyr 0.7.0 the following works without any special accommodations:

library("tidyverse")
# library("rlang")
my_cols <- c("Petal.Width", "Petal.Length")
iris %>%
  select(my_cols)

Note that in development builds of dplyr, this was not the case

Motivation

Selecting columns in Shiny apps is a good example use case, this is how one could do it using verb_ notation

library("shiny")
library("tidyverse")
library("DT")

shinyApp(
  ui = fluidPage(
    selectInput("cols_to_show",
                "Columns to show",
                choices = colnames(iris),
                multiple = TRUE),
    dataTableOutput("verb_table")
  ),
  server = function(input, output){
    output$verb_table <- renderDataTable({
      iris %>%
        select_(.dots = input$cols_to_show)

    })
  }
)