#' Block usage of `ifelse()` where `pmin()` or `pmax()` is more appropriate
#'
#' `ifelse(x > M, M, x)` is the same as `pmin(x, M)`, but harder
#' to read and requires several passes over the vector.
#'
#' The same goes for other similar ways to censor a vector, e.g.
#' `ifelse(x <= M, x, M)` is `pmin(x, M)`,
#' `ifelse(x < m, m, x)` is `pmax(x, m)`, and
#' `ifelse(x >= m, x, m)` is `pmax(x, m)`.
#'
#' @examples
#' # will produce lints
#' lint(
#' text = "ifelse(5:1 < pi, 5:1, pi)",
#' linters = ifelse_censor_linter()
#' )
#'
#' lint(
#' text = "ifelse(x > 0, x, 0)",
#' linters = ifelse_censor_linter()
#' )
#'
#' # okay
#' lint(
#' text = "pmin(5:1, pi)",
#' linters = ifelse_censor_linter()
#' )
#'
#' lint(
#' text = "pmax(x, 0)",
#' linters = ifelse_censor_linter()
#' )
#'
#' @evalRd rd_tags("ifelse_censor_linter")
#' @seealso [linters] for a complete list of linters available in lintr.
#' @export
ifelse_censor_linter <- function() {
xpath <- glue("
parent::expr
/following-sibling::expr[
(LT or GT or LE or GE)
and expr[1] = following-sibling::expr
and expr[2] = following-sibling::expr
]
/parent::expr
")
Linter(linter_level = "expression", function(source_expression) {
ifelse_calls <- source_expression$xml_find_function_calls(ifelse_funs)
bad_expr <- xml_find_all(ifelse_calls, xpath)
matched_call <- xp_call_name(bad_expr)
operator <- xml_find_chr(bad_expr, "string(expr[2]/*[2])")
match_first <- !is.na(xml_find_first(bad_expr, "expr[2][expr[1] = following-sibling::expr[1]]"))
optimizer <- ifelse((operator %in% c("<", "<=")) == match_first, "pmin", "pmax")
first_var <- rep_len("x", length(match_first))
second_var <- rep_len("y", length(match_first))
first_var[!match_first] <- "y"
second_var[!match_first] <- "x"
xml_nodes_to_lints(
bad_expr,
source_expression = source_expression,
lint_message = sprintf(
"%s(x, y) is preferable to %s(x %s y, %s, %s).",
optimizer, matched_call, operator, first_var, second_var
),
type = "warning"
)
})
}
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