#' Require usage of `expect_gt(x, y)` over `expect_true(x > y)` (and similar)
#'
#' [testthat::expect_gt()], [testthat::expect_gte()], [testthat::expect_lt()],
#' [testthat::expect_lte()], and [testthat::expect_equal()] exist specifically
#' for testing comparisons between two objects. [testthat::expect_true()] can
#' also be used for such tests, but it is better to use the tailored function
#' instead.
#'
#' @examples
#' # will produce lints
#' lint(
#' text = "expect_true(x > y)",
#' linters = expect_comparison_linter()
#' )
#'
#' lint(
#' text = "expect_true(x <= y)",
#' linters = expect_comparison_linter()
#' )
#'
#' lint(
#' text = "expect_true(x == (y == 2))",
#' linters = expect_comparison_linter()
#' )
#'
#' # okay
#' lint(
#' text = "expect_gt(x, y)",
#' linters = expect_comparison_linter()
#' )
#'
#' lint(
#' text = "expect_lte(x, y)",
#' linters = expect_comparison_linter()
#' )
#'
#' lint(
#' text = "expect_identical(x, y == 2)",
#' linters = expect_comparison_linter()
#' )
#'
#' lint(
#' text = "expect_true(x < y | x > y^2)",
#' linters = expect_comparison_linter()
#' )
#'
#' @evalRd rd_tags("expect_comparison_linter")
#' @seealso [linters] for a complete list of linters available in lintr.
#' @export
expect_comparison_linter <- function() {
# != doesn't have a clean replacement
comparator_nodes <- setdiff(infix_metadata$xml_tag[infix_metadata$comparator], "NE")
xpath <- glue("
parent::expr
/following-sibling::expr[1][ {xp_or(comparator_nodes)} ]
/parent::expr[not(SYMBOL_SUB[text() = 'info'])]
")
comparator_expectation_map <- c(
`>` = "expect_gt", `>=` = "expect_gte",
`<` = "expect_lt", `<=` = "expect_lte",
`==` = "expect_identical"
)
Linter(linter_level = "expression", function(source_expression) {
xml_calls <- source_expression$xml_find_function_calls("expect_true")
bad_expr <- xml_find_all(xml_calls, xpath)
comparator <- xml_find_chr(bad_expr, "string(expr[2]/*[2])")
expectation <- comparator_expectation_map[comparator]
lint_message <- sprintf("%s(x, y) is better than expect_true(x %s y).", expectation, comparator)
xml_nodes_to_lints(bad_expr, source_expression, lint_message = lint_message, type = "warning")
})
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.