Function argument linter

Check that arguments with defaults come last in all function declarations, as per the tidyverse design guide.

Changing the argument order can be a breaking change. An alternative to changing the argument order is to instead set the default for such arguments to NULL.

Usage

function_argument_linter()

See also

• linters for a complete list of linters available in lintr.

• https://design.tidyverse.org/required-no-defaults.html

Tags

best_practices, consistency, style

Examples

# will produce lints
lint(
  text = "function(y = 1, z = 2, x) {}",
  linters = function_argument_linter()
)
#> ::warning file=<text>,line=1,col=24::file=<text>,line=1,col=24,[function_argument_linter] Arguments without defaults should come before arguments with defaults.

lint(
  text = "function(x, y, z = 1, ..., w) {}",
  linters = function_argument_linter()
)
#> ::warning file=<text>,line=1,col=28::file=<text>,line=1,col=28,[function_argument_linter] Arguments without defaults should come before arguments with defaults.

# okay
lint(
  text = "function(x, y = 1, z = 2) {}",
  linters = function_argument_linter()
)

lint(
  text = "function(x, y, w, z = 1, ...) {}",
  linters = function_argument_linter()
)

lint(
  text = "function(y = 1, z = 2, x = NULL) {}",
  linters = function_argument_linter()
)

lint(
  text = "function(x, y, z = 1, ..., w = NULL) {}",
  linters = function_argument_linter()
)