fix: recover from corrupted persist file at package load (upstream #45)

Issue #45 (2021): persist-load raised End of file during parsing
at persist.el:413 in some configurations, likely from a corrupted
persist data file.  Pre-fix, this propagated up through the
top-level (persist-defvar org-drill-sm5-optimal-factor-matrix ...)
form at file-load time and broke the entire package's load.

Wrapped the persist-defvar form in condition-case.  On failure, the
matrix falls back to a fresh nil binding via plain defvar, and a
message tells the user what happened.  org-drill continues to load
normally.

1 files changed, 51 insertions, 0 deletions

diff --git a/tests/test-org-drill-persist-recovery.el b/tests/test-org-drill-persist-recovery.el
new file mode 100644
index 0000000..eb0b572
--- /dev/null
+++ b/tests/test-org-drill-persist-recovery.el
@@ -0,0 +1,51 @@
+;;; test-org-drill-persist-recovery.el --- Regression test for corrupted persist file  -*- lexical-binding: t; -*-
+
+;;; Commentary:
+;; Upstream issue #45 (2021-10).  `persist-load' raises "End of file
+;; during parsing" at persist.el:413 in some configurations, likely
+;; from a corrupted persist data file.  Pre-fix, this propagated up
+;; through the `(persist-defvar org-drill-sm5-optimal-factor-matrix
+;; ...)' form at file-load time, breaking the entire package's load.
+;;
+;; Fix wraps the persist-defvar form in `condition-case' so a
+;; corrupted file falls back to a fresh nil matrix instead of
+;; preventing the package from loading.
+
+;;; Code:
+
+(require 'ert)
+(require 'cl-lib)
+(require 'persist)
+(require 'org-drill)
+
+;;;; Regression — wrapping pattern
+
+(ert-deftest test-persist-defvar-error-falls-back-to-initial-value ()
+  "When persist-load throws, the condition-case wrapper recovers and
+binds the symbol to the supplied initial value.
+
+This verifies the same wrapping pattern used at top-level around the
+real `org-drill-sm5-optimal-factor-matrix' definition."
+  (let ((sym (intern (format "org-drill-test-persist-sym-%d" (random 999999)))))
+    (unwind-protect
+        (progn
+          (cl-letf (((symbol-function 'persist-symbol) #'ignore)
+                    ((symbol-function 'persist-load)
+                     (lambda (_) (error "End of file during parsing"))))
+            (condition-case _err
+                (eval `(persist-defvar ,sym 'fallback-value "doc"))
+              (error
+               (set sym 'fallback-value))))
+          (should (eq 'fallback-value (symbol-value sym))))
+      ;; Clean up the test symbol.
+      (when (boundp sym) (makunbound sym)))))
+
+(ert-deftest test-org-drill-sm5-optimal-factor-matrix-bound ()
+  "After loading org-drill, the SM5 matrix variable is bound — confirms
+the at-load-time wrapping (or normal persist-defvar success) leaves
+the package in a usable state."
+  (should (boundp 'org-drill-sm5-optimal-factor-matrix)))
+
+(provide 'test-org-drill-persist-recovery)
+
+;;; test-org-drill-persist-recovery.el ends here