Check for a common mistake where length is applied in the wrong place

Usage like length(x == 0) is a mistake. If you intended to check x is empty, use length(x) == 0. Other mistakes are possible, but running length() on the outcome of a logical comparison is never the best choice.

Usage

length_test_linter()

See also

linters for a complete list of linters available in lintr.

Tags

best_practices, consistency, robustness

Examples

# will produce lints
lint(
  text = "length(x == 0)",
  linters = length_test_linter()
)
#> <text>:1:1: warning: [length_test_linter] Checking the length of a logical vector is likely a mistake. Did you mean `length(x) == 0`?
#> length(x == 0)
#> ^~~~~~~~~~~~~~

# okay
lint(
  text = "length(x) > 0",
  linters = length_test_linter()
)
#> ℹ No lints found.