In dgkf/reflow: What the Package Does (One Line, Title Case)

reflow

An experimental linter and formatter designed as a syntax pattern matching DSL.

Status

Right now this is entirely a proof of concept. The examples may break or change as the package develops, and there are no guarantees that this will ever mature into something stable.

Goals

Make syntax styles easier to express, validate and apply
Apply style logic in a minimal traversal of the syntax tree.
Make composition of styles easy, built upon minimal rules

Examples

library(reflow)
options(reflow.quiet = FALSE)

# define a set of linter rules
rs <- rules(
  "function header opening paren should not be preceded by whitespace" = rule(
    "function", ws(0), "expr"
  ),
  "function header closing paren should be followed by a space or newline" = rule(
    "function", "expr", either_token(ws(1), ws(nl = 1)), any_token()
  ),
  "parameter assignments should always be surrounded by single spaces" = rule(
    on = "eq_formals",
    ws(1), "=", ws(1)
  ),
  "multiline expressions should be indented by one level" = rule(
    "{",
    ws(nl = 1),
    indent(zero_or_more(any_token(), until = "}")),
    ws(nl = 1),
    "}"
  )
)

# match the rules against a block of code
match_style(rs, "
test <- function()  1L

test <- function (a = 1L, b  = 3){
   1 + 2L
  {
    1 + 2
  }
}
")

<<text> 2:21>
1▕
2▕ test <- function()  1L
                       ^
function header closing paren should be followed by a space or newline

<<text> 4:18>
2▕ test <- function()  1L
3▕
4▕ test <- function (a = 1L, b  = 3){
                    ^
function header opening paren should not be preceded by whitespace

<<text> 4:34>
2▕ test <- function()  1L
3▕
4▕ test <- function (a = 1L, b  = 3){
                                    ^
function header closing paren should be followed by a space or newline

<<text> 4:30>
2▕ test <- function()  1L
3▕
4▕ test <- function (a = 1L, b  = 3){
                                ^
parameter assignments should always be surrounded by single spaces

<<text> 5:4>
3▕
4▕ test <- function (a = 1L, b  = 3){
5▕    1 + 2L
      ^
multiline expressions should be indented by one level