From b2cc4d1645b378043a971906b5ebc34d3c92b544 Mon Sep 17 00:00:00 2001
From: Craig Jennings <c@cjennings.net>
Date: Tue, 5 May 2026 04:29:28 -0500
Subject: fix: guard org-drill-smart-reschedule cond against nil days-ahead
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The function takes `days-ahead' as &optional, but the schedule cond
called `(= 0 days-ahead)' and `(cl-minusp days-ahead)' before any
type-guard, so passing nil crashed with a wrong-type-argument error.

Today's two callers (the rating-confirmation flow and the
org-drill-relearn-item helper) always pass a number, so this was
latent — but a third caller relying on the documented &optional
shape would hit it immediately.

Switched the cond to require numberp before the value comparisons,
and the default branch now falls back to the algorithm-computed
next-interval when days-ahead is nil.  That matches the intent
implied by the optional signature and the docstring.
---
 org-drill.el | 15 ++++++++++-----
 1 file changed, 10 insertions(+), 5 deletions(-)

diff --git a/org-drill.el b/org-drill.el
index dd210a2..fe99a3f 100644
--- a/org-drill.el
+++ b/org-drill.el
@@ -1429,15 +1429,20 @@ item will be scheduled exactly this many days into the future."
         (if (eql 'sm5 org-drill-spaced-repetition-algorithm)
             (setq org-drill-sm5-optimal-factor-matrix new-ofmatrix))
 
+        ;; Pick the schedule based on days-ahead.  The optional arg may be
+        ;; nil (callers omit it to mean "use the algorithm-computed
+        ;; next-interval").  The original cond compared `(= 0 days-ahead)'
+        ;; before any type guard, which crashed on nil.
         (cond
-         ((= 0 days-ahead)
+         ((and (numberp days-ahead) (= 0 days-ahead))
           (org-schedule '(4)))
-         ((cl-minusp days-ahead)
+         ((and (numberp days-ahead) (cl-minusp days-ahead))
           (org-schedule nil (current-time)))
          (t
-          (org-schedule nil (time-add (current-time)
-                                      (days-to-time
-                                       (round next-interval))))))))))
+          (let ((interval (if (numberp days-ahead) days-ahead next-interval)))
+            (org-schedule nil (time-add (current-time)
+                                        (days-to-time
+                                         (round interval)))))))))))
 
 (defun org-drill-hypothetical-next-review-date (quality)
   "Returns an integer representing the number of days into the future
-- 
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