Block statements like if (!A) x else y

if (!A) x else y is the same as if (A) y else x, but the latter is easier to reason about in the else case. The former requires double negation that can be avoided by switching the statement order.

Usage

if_not_else_linter(exceptions = c("is.null", "is.na", "missing"))

Arguments

exceptions

Character vector of calls to exclude from linting. By default, is.null(), is.na(), and missing() are excluded given the common idiom !is.na(x) as "x is present".

Details

This only applies in the simple if/else case. Statements like if (!A) x else if (B) y else z don't always have a simpler or more readable form.

It also applies to ifelse() and the package equivalents dplyr::if_else() and data.table::fifelse().

See also

linters for a complete list of linters available in lintr.

Tags

configurable, consistency, readability

Examples

# will produce lints
lint(
  text = "if (!A) x else y",
  linters = if_not_else_linter()
)
#> <text>:1:5: warning: [if_not_else_linter] Prefer `if (A) x else y` to the less-readable `if (!A) y else x` in a simple if/else statement.
#> if (!A) x else y
#>     ^~

lint(
  text = "if (!A) x else if (!B) y else z",
  linters = if_not_else_linter()
)
#> <text>:1:20: warning: [if_not_else_linter] Prefer `if (A) x else y` to the less-readable `if (!A) y else x` in a simple if/else statement.
#> if (!A) x else if (!B) y else z
#>                    ^~

lint(
  text = "ifelse(!is_treatment, x, y)",
  linters = if_not_else_linter()
)
#> <text>:1:1: warning: [if_not_else_linter] Prefer `ifelse(A, x, y)` to the less-readable `ifelse(!A, y, x)`.
#> ifelse(!is_treatment, x, y)
#> ^~~~~~~~~~~~~~~~~~~~~~~~~~~

lint(
  text = "if (!is.null(x)) x else 2",
  linters = if_not_else_linter(exceptions = character())
)
#> <text>:1:5: warning: [if_not_else_linter] Prefer `if (A) x else y` to the less-readable `if (!A) y else x` in a simple if/else statement.
#> if (!is.null(x)) x else 2
#>     ^~~~~~~~~~~

# okay
lint(
  text = "if (A) x else y",
  linters = if_not_else_linter()
)
#> ℹ No lints found.

lint(
  text = "if (!A) x else if (B) z else y",
  linters = if_not_else_linter()
)
#> ℹ No lints found.

lint(
  text = "ifelse(is_treatment, y, x)",
  linters = if_not_else_linter()
)
#> ℹ No lints found.

lint(
  text = "if (!is.null(x)) x else 2",
  linters = if_not_else_linter()
)
#> ℹ No lints found.