feat: add org-drill-treat-headline-as-card-p for empty-bodied cards

A drill entry with an empty body is skipped unless its card type opts into empty bodies via the DRILL-EMPTY-P slot of org-drill-card-type-alist. That left no global way to drill headline-only items, or hierarchical-notes decks where the heading is the question and the answer lives in child entries (upstream #30, #41).

I added org-drill-treat-headline-as-card-p, default nil so existing decks are unchanged. When it's on, the empty-skip gate in org-drill--entry-empty-and-not-empty-friendly-p short-circuits, so every empty-bodied entry is drilled with its heading as the question regardless of card type. I added the safe-local-variable booleanp declaration alongside the other booleans and documented the switch in org-drill.org.

Tests pin the predicate and the classify-status outcome both on and off, and confirm the per-card-type DRILL-EMPTY-P path stays independent of the new switch.

1 files changed, 87 insertions, 0 deletions

diff --git a/tests/test-org-drill-treat-headline-as-card.el b/tests/test-org-drill-treat-headline-as-card.el
new file mode 100644
index 0000000..5b369e7
--- /dev/null
+++ b/tests/test-org-drill-treat-headline-as-card.el
@@ -0,0 +1,87 @@
+;;; test-org-drill-treat-headline-as-card.el --- Tests for headline-as-card  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; `org-drill-treat-headline-as-card-p' controls whether a drill entry with an
+;; empty body is skipped (the default) or presented as a card with the heading
+;; itself as the question (upstream issues #30 and #41).
+;;
+;; The gate lives in `org-drill--entry-empty-and-not-empty-friendly-p', whose
+;; non-nil result makes `org-drill--classify-status' return nil (the entry is
+;; not a drillable card).  These tests pin both the predicate and the
+;; classification outcome, on and off, and confirm the per-card-type
+;; DRILL-EMPTY-P mechanism still works independently of the new global switch.
+
+;;; Code:
+
+(require 'ert)
+(require 'org-drill)
+
+;;;; Defcustom default
+
+(ert-deftest test-org-drill-treat-headline-as-card-defaults-off ()
+  "The defcustom ships nil so existing decks keep skipping empty entries."
+  (should (eq nil (default-value 'org-drill-treat-headline-as-card-p))))
+
+;;;; Predicate — org-drill--entry-empty-and-not-empty-friendly-p
+
+(ert-deftest test-org-drill-empty-entry-skipped-when-headline-card-off ()
+  "With the switch off, an empty-bodied drill entry is treated as
+empty-and-skippable (predicate returns non-nil)."
+  (let ((org-drill-treat-headline-as-card-p nil))
+    (with-temp-buffer
+      (insert "* A headline-only card :drill:\n")
+      (org-mode)
+      (goto-char (point-min))
+      (should (org-drill--entry-empty-and-not-empty-friendly-p)))))
+
+(ert-deftest test-org-drill-empty-entry-not-skipped-when-headline-card-on ()
+  "With the switch on, an empty-bodied drill entry is NOT skippable
+\(predicate returns nil) — the heading becomes the card."
+  (let ((org-drill-treat-headline-as-card-p t))
+    (with-temp-buffer
+      (insert "* A headline-only card :drill:\n")
+      (org-mode)
+      (goto-char (point-min))
+      (should-not (org-drill--entry-empty-and-not-empty-friendly-p)))))
+
+(ert-deftest test-org-drill-non-empty-entry-not-skipped-regardless ()
+  "An entry with a body is never empty-and-skippable, switch on or off."
+  (dolist (flag '(nil t))
+    (let ((org-drill-treat-headline-as-card-p flag))
+      (with-temp-buffer
+        (insert "* A normal card :drill:\nThe answer body.\n")
+        (org-mode)
+        (goto-char (point-min))
+        (should-not (org-drill--entry-empty-and-not-empty-friendly-p))))))
+
+(ert-deftest test-org-drill-empty-friendly-card-type-unaffected-by-switch ()
+  "A card type that opts into empty bodies via DRILL-EMPTY-P (e.g. twosided)
+is never skippable, independent of the global switch."
+  (dolist (flag '(nil t))
+    (let ((org-drill-treat-headline-as-card-p flag))
+      (with-temp-buffer
+        (insert "* A two-sided card :drill:\n"
+                ":PROPERTIES:\n:DRILL_CARD_TYPE: twosided\n:END:\n")
+        (org-mode)
+        (goto-char (point-min))
+        (should-not (org-drill--entry-empty-and-not-empty-friendly-p))))))
+
+;;;; Classification outcome — org-drill--classify-status
+
+(ert-deftest test-org-drill-classify-empty-entry-flips-with-switch ()
+  "An empty drill entry classifies as nil (skipped) with the switch off, and
+as a real status with the switch on — the user-facing effect of the feature."
+  (with-temp-buffer
+    (insert "* A headline-only card :drill:\n")
+    (org-mode)
+    (goto-char (point-min))
+    ;; due=nil reaches :unscheduled only once the empty gate is passed; session
+    ;; is unused on that path, so nil is safe here.
+    (let ((org-drill-treat-headline-as-card-p nil))
+      (should (null (org-drill--classify-status nil nil 1))))
+    (let ((org-drill-treat-headline-as-card-p t))
+      (should (org-drill--classify-status nil nil 1)))))
+
+(provide 'test-org-drill-treat-headline-as-card)
+
+;;; test-org-drill-treat-headline-as-card.el ends here