Create a style guide — create_style

This is a helper function to create a style guide, which is technically speaking a named list of groups of transformer functions where each transformer function corresponds to one styling rule. The output of this function can be used as an argument for style in top-level functions like style_text() and friends. Note that for caching to work properly, unquote all inputs to the transformer function if possible with rlang's !!, otherwise, they will be passed as references (generic variable names) instead of literals and styler:::is_cached() won't pick up changes. See how it's done in tidyverse_style() with indent_by and other arguments.

create_style_guide(
  initialize = default_style_guide_attributes,
  line_break = NULL,
  space = NULL,
  token = NULL,
  indention = NULL,
  use_raw_indention = FALSE,
  reindention = tidyverse_reindention(),
  style_guide_name = NULL,
  style_guide_version = NULL,
  more_specs_style_guide = NULL,
  transformers_drop = specify_transformers_drop(),
  indent_character = " "
)

Arguments

initialize: The bare name of a function that initializes various variables on each level of nesting.
line_break: A list of transformer functions that manipulate line_break information.
space: A list of transformer functions that manipulate spacing information.
token: A list of transformer functions that manipulate token text.
indention: A list of transformer functions that manipulate indention.
use_raw_indention: Boolean indicating whether or not the raw indention should be used.
reindention: A list of parameters for regex re-indention, most conveniently constructed using specify_reindention().
style_guide_name: The name of the style guide. Used as a meta attribute inside the created style guide, for example for caching. By convention, this is the style guide qualified by the package namespace plus the location of the style guide, separated by @. For example, "styler::tidyverse_style@https://github.com/r-lib".
style_guide_version: The version of the style guide. Used as a meta attribute inside the created style guide, for example for caching. This should correspond to the version of the R package that exports the style guide.
more_specs_style_guide: Named vector (coercible to character) with all arguments passed to the style guide and used for cache invalidation. You can easily capture them in your style guide function declaration with as.list(environment()) (compare source code of tidyverse_style()).
transformers_drop: A list specifying under which conditions transformer functions can be dropped since they have no effect on the code to format, most easily constructed with specify_transformers_drop(). This is argument experimental and may change in future releases without prior notification. It was mainly introduced to improve speed. Listing transformers here that occur almost always in code does not make sense because the process of excluding them also takes some time.
indent_character: The character that is used for indention. We strongly advise for using spaces as indention characters.

Examples

set_line_break_before_curly_opening <- function(pd_flat) {
  op <- pd_flat$token %in% "'{'"
  pd_flat$lag_newlines[op] <- 1L
  pd_flat
}
set_line_break_before_curly_opening_style <- function() {
  create_style_guide(
    line_break = list(set_line_break_before_curly_opening),
    style_guide_name = "some-style-guide",
    style_guide_version = "some-version"
  )
}
style_text(
  "a <- function(x) { x }",
  style = set_line_break_before_curly_opening_style
)
#> a <- function(x)
#> { x }