Validate backend history and order choices

Author: tninja

ai-code-backends.el

@@ -27,6 +27,8 @@
 (defvar ai-code--cli-resume-fn #'ai-code--unsupported-resume)
 (defvar ai-code--cli-switch-fn #'ai-code--unsupported-switch-to-buffer)
 (defvar ai-code--cli-send-fn #'ai-code--unsupported-send-command)
+(defvar ai-code-selected-backend 'claude-code
+  "Currently selected backend key from `ai-code-backends'.")
 
 (defvar ai-code--repo-backend-alist nil
   "Alist of (GIT-ROOT . BACKEND) to keep backend affinity per repository.")
@@ -427,6 +429,18 @@ configuration paths, upgrade commands, and skill-install commands."
   (expand-file-name "ai-code-backends-history.el" user-emacs-directory)
   "File path to store the MRU history of selected backends.")
 
+(defun ai-code--delete-backends-history-file ()
+  "Delete `ai-code-backends-history-file' when it exists."
+  (when (file-exists-p ai-code-backends-history-file)
+    (ignore-errors (delete-file ai-code-backends-history-file))))
+
+(defun ai-code--valid-backends-history-p (history)
+  "Return non-nil when HISTORY is a list of backend symbols."
+  (and (listp history)
+       (seq-every-p (lambda (item)
+                      (and item (symbolp item)))
+                    history)))
+
 (defun ai-code--load-backends-history ()
   "Load the MRU backend history from `ai-code-backends-history-file'."
   (if (file-exists-p ai-code-backends-history-file)
@@ -435,9 +449,13 @@ configuration paths, upgrade commands, and skill-install commands."
             (insert-file-contents ai-code-backends-history-file)
             (let ((content (buffer-string)))
               (unless (string-empty-p content)
-                (read content))))
+                (let ((history (read content)))
+                  (if (ai-code--valid-backends-history-p history)
+                      history
+                    (ai-code--delete-backends-history-file)
+                    nil)))))
         (error
-         (ignore-errors (delete-file ai-code-backends-history-file))
+         (ai-code--delete-backends-history-file)
          nil))
     nil))
 
@@ -451,9 +469,6 @@ configuration paths, upgrade commands, and skill-install commands."
                     (prin1-to-string updated-history))))
       (error nil))))
 
-(defvar ai-code-selected-backend 'claude-code
-  "Currently selected backend key from `ai-code-backends'.")
-
 (defun ai-code-set-backend (new-backend)
   "Set the AI backend to NEW-BACKEND."
   (unless (ai-code--backend-spec new-backend)
@@ -467,6 +482,35 @@ configuration paths, upgrade commands, and skill-install commands."
   "Return backend plist for KEY from `ai-code-backends'."
   (seq-find (lambda (it) (eq (car it) key)) ai-code-backends))
 
+(defun ai-code--ordered-backend-choices ()
+  "Return backend choices with the effective backend first, then MRU entries."
+  (let* ((choices (mapcar (lambda (it)
+                            (let* ((key (car it))
+                                   (label (plist-get (cdr it) :label)))
+                              (cons (format "%s" label) key)))
+                          ai-code-backends))
+         (effective-backend (ai-code--effective-backend))
+         (history (ai-code--load-backends-history))
+         (history-choices (seq-filter #'identity
+                                      (mapcar (lambda (key)
+                                                (seq-find (lambda (candidate)
+                                                            (eq (cdr candidate) key))
+                                                          choices))
+                                              history)))
+         (other-choices (seq-remove (lambda (candidate)
+                                      (member candidate history-choices))
+                                    choices))
+         (sorted-choices (append history-choices other-choices))
+         (current-choice (seq-find (lambda (candidate)
+                                     (eq (cdr candidate) effective-backend))
+                                   sorted-choices)))
+    (if current-choice
+        (cons current-choice
+              (seq-remove (lambda (candidate)
+                            (eq (cdr candidate) effective-backend))
+                          sorted-choices))
+      sorted-choices)))
+
 (defun ai-code-current-backend-label ()
   "Return label string of the currently selected backend.
 Falls back to symbol name when label is unavailable."
@@ -542,25 +586,11 @@ invoke `ai-code-cli-resume'; otherwise call `ai-code-cli-start'."
 (defun ai-code-select-backend ()
   "Interactively select and apply an AI backend from `ai-code-backends'."
   (interactive)
-  (let* ((choices (mapcar (lambda (it)
-                            (let* ((key (car it))
-                                   (label (plist-get (cdr it) :label)))
-                              (cons (format "%s" label) key)))
-                          ai-code-backends))
-         (effective-backend (ai-code--effective-backend))
-         (history (ai-code--load-backends-history))
-         (history-choices (seq-filter #'identity
-                                      (mapcar (lambda (key)
-                                                (seq-find (lambda (c) (eq (cdr c) key)) choices))
-                                              history)))
-         (other-choices (seq-remove (lambda (c) (member c history-choices)) choices))
-         (sorted-choices (append history-choices other-choices))
-         (current-choice (seq-find (lambda (it) (eq (cdr it) effective-backend)) sorted-choices))
-         (ordered-choices (if current-choice
-                              (cons current-choice
-                                    (seq-remove (lambda (it) (eq (cdr it) effective-backend))
-                                                sorted-choices))
-                            sorted-choices))
+  (let* ((ordered-choices (ai-code--ordered-backend-choices))
+         (current-choice (car ordered-choices))
+         (completion-extra-properties
+          '(:display-sort-function identity
+            :cycle-sort-function identity))
          (choice (completing-read "Select backend: "
                                   (mapcar #'car ordered-choices)
                                   nil t nil nil (car current-choice)))

test/test_ai-code-backends.el

@@ -414,6 +414,7 @@
                               (backend-c :label "Backend C" :start ignore :switch ignore :send ignore)))
          (ai-code-selected-backend 'backend-a)
          (captured-candidates nil)
+         (captured-extra-properties nil)
          (selected-choice "Backend B"))
     (unwind-protect
         (progn
@@ -425,6 +426,7 @@
           (cl-letf (((symbol-function 'completing-read)
                      (lambda (_prompt candidates &rest _args)
                        (setq captured-candidates candidates)
+                       (setq captured-extra-properties completion-extra-properties)
                        selected-choice))
                     ((symbol-function 'ai-code-onboarding-show-backend-switch-hint) #'ignore)
                     ((symbol-function 'message) #'ignore))
@@ -438,6 +440,10 @@
             ;;   - Then: history items in order (backend-c, backend-b) excluding current
             ;; So candidates should be '("Backend A" "Backend C" "Backend B")
             (should (equal captured-candidates '("Backend A" "Backend C" "Backend B")))
+            (should (eq (plist-get captured-extra-properties :display-sort-function)
+                        #'identity))
+            (should (eq (plist-get captured-extra-properties :cycle-sort-function)
+                        #'identity))
 
             ;; 3. The history file should have been updated after selection:
             ;; New selection B is now at the top, C is next
@@ -466,6 +472,19 @@
       (when (file-exists-p temp-file)
         (delete-file temp-file)))))
 
+(ert-deftest ai-code-test-backends-readable-malformed-history-file-deleted ()
+  "Test that readable but malformed history content is discarded."
+  (let* ((temp-file (make-temp-file "ai-code-backends-history-"))
+         (ai-code-backends-history-file temp-file))
+    (unwind-protect
+        (progn
+          (write-region "backend-b" nil temp-file nil 'silent)
+          (should (file-exists-p temp-file))
+          (should-not (ai-code--load-backends-history))
+          (should-not (file-exists-p temp-file)))
+      (when (file-exists-p temp-file)
+        (delete-file temp-file)))))
+
 (ert-deftest ai-code-test-select-backend-partial-history-keeps-all-backends ()
   "Test that even if the history file only covers some backends or contains invalid keys, all backends are still available as choices."
   (let* ((temp-file (make-temp-file "ai-code-backends-history-"))