refactor(org-drill): share one validated drill-file selector

org-capture-config.el and org-drill-config.el each scanned drill-dir with an inline directory-files call, so a missing, empty, or unreadable drill-dir surfaced as a low-level directory-files error or an empty completing-read, depending on which command ran. Added cj/--drill-files-or-error, the single validated entry point: it signals a clear user-error when the directory is missing, unreadable, or has no drill files, and otherwise returns the list. cj/--drill-pick-file and both drill capture templates now route through it. The pure cj/--drill-files-in primitive and its tests are unchanged. Tests cover missing dir, empty dir, a non-org-only dir, and a normal listing.

3 files changed, 73 insertions, 11 deletions

diff --git a/modules/org-capture-config.el b/modules/org-capture-config.el
index 5cd76f0a..39cafe03 100644
--- a/modules/org-capture-config.el
+++ b/modules/org-capture-config.el
@@ -18,6 +18,7 @@
 (defvar org-capture-templates)
 (defvar org-complex-heading-regexp-format)
 
+(declare-function cj/--drill-pick-file "org-drill-config")
 (declare-function org-at-encrypted-entry-p "org-crypt")
 (declare-function org-at-heading-p "org")
 (declare-function org-back-to-heading "org")
@@ -230,21 +231,13 @@ Captured On: %U"
            :prepend t)
 
           ("d" "Drill Question" entry
-           (file (lambda ()
-                   (let ((files (directory-files drill-dir nil "^[^.].*\\.org$")))
-                     (expand-file-name
-                      (completing-read "Choose file: " files)
-                      drill-dir))))
+           (file (lambda () (cj/--drill-pick-file drill-dir)))
            "* Item   :drill:\n%?
 ** Answer\n%i\nSource: [[%:link][%:description]]
 Captured On: %U" :prepend t)
 
           ("f" "Drill Question (from PDF)" entry
-           (file (lambda ()
-                   (let ((files (directory-files drill-dir nil "^[^.].*\\.org$")))
-                     (expand-file-name
-                      (completing-read "Choose file: " files)
-                      drill-dir))))
+           (file (lambda () (cj/--drill-pick-file drill-dir)))
            "* Item   :drill:\n%?
 ** Answer\n%(cj/org-capture-pdf-active-region)
 Source: [[%L][%(buffer-name (org-capture-get :original-buffer))]]
diff --git a/modules/org-drill-config.el b/modules/org-drill-config.el
index 79fdb027..c3852ed1 100644
--- a/modules/org-drill-config.el
+++ b/modules/org-drill-config.el
@@ -32,10 +32,23 @@
   "Return the drill Org file names directly inside DIR (no leading dots)."
   (directory-files dir nil "^[^.].*\\.org$"))
 
+(defun cj/--drill-files-or-error (dir)
+  "Return the drill Org files in DIR, or signal a clear `user-error'.
+Errors when DIR is missing, unreadable, or has no drill files, so callers
+fail with an actionable message instead of a low-level `directory-files'
+error or an empty `completing-read'.  This is the single entry point the
+drill commands and the drill capture templates share."
+  (unless (and (file-directory-p dir) (file-readable-p dir))
+    (user-error "Drill directory missing or unreadable: %s" dir))
+  (let ((files (cj/--drill-files-in dir)))
+    (unless files
+      (user-error "No drill files (.org) found in %s" dir))
+    files))
+
 (defun cj/--drill-pick-file (dir)
   "Prompt for one of the drill Org files in DIR; return its absolute path."
   (expand-file-name
-   (completing-read "Choose flashcard file: " (cj/--drill-files-in dir) nil t)
+   (completing-read "Choose flashcard file: " (cj/--drill-files-or-error dir) nil t)
    dir))
 
 (defun cj/--drill-pick-dir (other-dir)
diff --git a/tests/test-org-drill-config--drill-files-or-error.el b/tests/test-org-drill-config--drill-files-or-error.el
new file mode 100644
index 00000000..3b980358
--- /dev/null
+++ b/tests/test-org-drill-config--drill-files-or-error.el
@@ -0,0 +1,56 @@
+;;; test-org-drill-config--drill-files-or-error.el --- Tests for validated drill file listing -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Unit tests for cj/--drill-files-or-error, the single validated entry point
+;; that drill capture templates and the drill commands share.  It returns the
+;; drill files in a directory or signals a clear `user-error' when the
+;; directory is missing, unreadable, or empty — instead of leaking a low-level
+;; error from `directory-files' or handing `completing-read' an empty list.
+
+;;; Code:
+
+(require 'ert)
+
+(add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
+(require 'org-drill-config)
+
+;;; Normal Cases
+
+(ert-deftest test-org-drill--files-or-error-normal-lists-org-files ()
+  "Normal: a directory with drill files returns their names."
+  (let ((dir (make-temp-file "cj-drill-or-error-" t)))
+    (unwind-protect
+        (progn
+          (write-region "" nil (expand-file-name "a.org" dir))
+          (write-region "" nil (expand-file-name "b.org" dir))
+          (should (equal '("a.org" "b.org")
+                         (cj/--drill-files-or-error dir))))
+      (delete-directory dir t))))
+
+;;; Boundary Cases
+
+(ert-deftest test-org-drill--files-or-error-boundary-empty-dir-signals ()
+  "Boundary: an existing but empty directory signals a clear user-error."
+  (let ((dir (make-temp-file "cj-drill-or-error-empty-" t)))
+    (unwind-protect
+        (should-error (cj/--drill-files-or-error dir) :type 'user-error)
+      (delete-directory dir t))))
+
+(ert-deftest test-org-drill--files-or-error-boundary-only-non-org-signals ()
+  "Boundary: a directory with no .org files signals a user-error."
+  (let ((dir (make-temp-file "cj-drill-or-error-nonorg-" t)))
+    (unwind-protect
+        (progn
+          (write-region "" nil (expand-file-name "notes.txt" dir))
+          (should-error (cj/--drill-files-or-error dir) :type 'user-error))
+      (delete-directory dir t))))
+
+;;; Error Cases
+
+(ert-deftest test-org-drill--files-or-error-missing-dir-signals-user-error ()
+  "Error: a missing directory signals a `user-error', not a low-level error."
+  (should-error (cj/--drill-files-or-error "/no/such/cj-drill/dir/")
+                :type 'user-error))
+
+(provide 'test-org-drill-config--drill-files-or-error)
+;;; test-org-drill-config--drill-files-or-error.el ends here