From 14dd1183116e4ed58884ce9a5ccef10f325192b7 Mon Sep 17 00:00:00 2001
From: Maximilian Held <info@maxheld.de>
Date: Thu, 12 Sep 2024 17:18:45 +0200
Subject: [PATCH] make skip if not functions

---
 NAMESPACE                   |  1 +
 R/tests.R                   | 44 ++++++++++++++++++++++++++++++++++++-
 tests/testthat/test-tests.R |  9 ++++++++
 3 files changed, 53 insertions(+), 1 deletion(-)
 create mode 100644 tests/testthat/test-tests.R

diff --git a/NAMESPACE b/NAMESPACE
index c4af25c..ae2fe89 100644
--- a/NAMESPACE
+++ b/NAMESPACE
@@ -1,6 +1,7 @@
 # Generated by roxygen2: do not edit by hand
 
 export(is_installed2)
+export(make_skip_if_not_function)
 export(opt_set_local2)
 export(source_pef)
 export(transform_with_generated)
diff --git a/R/tests.R b/R/tests.R
index 2c0fee6..855d004 100644
--- a/R/tests.R
+++ b/R/tests.R
@@ -2,7 +2,7 @@
 #'
 #' To be used as an argument for [testthat::expect_snapshot()].
 #' @param x A character vector.
-#' @keywords snapshot helpers
+#' @keywords snapshot helpers, testing helpers
 #' @name transform_snap
 NULL
 
@@ -16,3 +16,45 @@ transform_with_generated <- function(x = character()) {
     x
   )
 }
+
+#' Make a [testthat::skip_if_not()] function
+#'
+#' Function operator to turn
+#' [checkmate](https://mllg.github.io/checkmate/index.html)'s
+#' `check_*()`-type functions into [testthat](https://testthat.r-lib.org)'s
+#' `skip_if_not_*()` functions.
+#'
+#' @inheritParams checkmate::makeAssertionFunction
+#' @details
+#' Notice that `check_*()` are always formulated *positively*;
+#' the message from `check_*()` is emitted,
+#' when its condition is *not* met.
+#' The [testthat](https://testthat.r-lib.org) equivalent is the opposite:
+#' a `skip_if_not_*()` function would skip with the emitted message.
+#'
+#' You cannot generate `skip_if_*()` functions from `check_*()` functions,
+#' because the negation of the emitted message may be wrong or confusing.
+#' But you can create one manually:
+#'
+#' ```r
+#' skip_if_cond <- function(x) {
+#'   testthat::skip_if(
+#'     my_pkg::check_cond(x),
+#'     # needs a custom message here
+#'     "Skipping because condition is true."
+#'   )
+#' }
+#' ```
+#' @export
+#' @keywords testing helpers
+make_skip_if_not_function <- function(check.fun) {
+  force(check.fun)
+  function(...) {
+    res <- check.fun(...)
+    if (isTRUE(res)) {
+      return(invisible())
+    } else {
+      testthat::skip(res)
+    }
+  }
+}
diff --git a/tests/testthat/test-tests.R b/tests/testthat/test-tests.R
new file mode 100644
index 0000000..b681dc3
--- /dev/null
+++ b/tests/testthat/test-tests.R
@@ -0,0 +1,9 @@
+describe("make_skip_if_not_function", {
+  it("returns invisibly if success", {
+    expect_equal(
+      make_skip_if_not_function(checkmate::check_scalar)(1),
+      invisible()
+    )
+  })
+  # can't easily test for failure, because then it would, well, skip.
+})