Formatting

Arity formats R source, roxygen comments, and package DESCRIPTION files. Start with installation, then run the formatter from your project directory.

Format Files

Format one file in place, or pass a directory to format the files inside it:

arity format R/example.R
arity format .

You can pass several files or directories in one invocation. Directory walks honor .gitignore and the exclusions in arity.toml. They include package-root DESCRIPTION files as well as R source. See Configuration to exclude generated or vendored files.

Check Without Writing

Use --check to report files that need formatting without changing them:

arity format --check .

Arity prints a diff for each file that would change and exits nonzero if any need formatting. Add --quiet to show the file list and summary without the diffs. See Integrations to run this check in CI or pre-commit.

Format Standard Input

Pass - to read a buffer from standard input and write the formatted text to standard output:

cat R/example.R | arity format -

Standard input is treated as R source unless you supply --stdin-filename. For a package description, use:

cat DESCRIPTION | arity format --stdin-filename DESCRIPTION -

--check requires file paths. For an editor buffer, consume the formatted standard output instead. Editor Setup covers the language server and RStudio integration.

Choose Formatting Settings

Put shared settings in arity.toml so the CLI and language server use the same style:

[format]
line-width = 100
indent-width = 2

For a single run, use arity format --line-width 100 R/example.R. The configuration reference describes every setting, including line endings and the switches for roxygen and DESCRIPTION formatting. DESCRIPTION continuation lines use four spaces regardless of the R indentation setting.

Preserve Selected Layout

Use a formatter directive when a particular statement needs hand-written layout:

# arity-format skip: the rows show the matrix layout
m <- matrix(c(1, 0,
              0, 1), nrow = 2)

# arity-format off and # arity-format on protect a region, and # arity-format skip-file protects a whole file. These spellings leave linting enabled. See Directives for their scope and the special rules for DESCRIPTION files.