fix(modeline): drop per-render truename, guard vc fetch against signals

The VC modeline cache rebuilt its key every render, and the key included file-truename, so a stat ran on every redisplay rather than once per refresh as the comment claimed. Now it keys on (file show-remote). A moved symlink target is caught at the next TTL refresh, when vc-backend resolves the link fresh. And cj/modeline-vc-fetch is wrapped in condition-case returning nil, so a git signal on a slow or unmounted filesystem degrades to no-VC-info instead of breaking all redisplay.

2 files changed, 27 insertions, 40 deletions

diff --git a/tests/test-modeline-config-vc-cache-key.el b/tests/test-modeline-config-vc-cache-key.el
index ae869f4b8..6ba7985c2 100644
--- a/tests/test-modeline-config-vc-cache-key.el
+++ b/tests/test-modeline-config-vc-cache-key.el
@@ -1,56 +1,36 @@
 ;;; test-modeline-config-vc-cache-key.el --- Tests for VC modeline cache key -*- lexical-binding: t; -*-
 
 ;;; Commentary:
-;; The VC modeline cache keys on the file.  A symlink whose target moves to a
-;; different VC tree must invalidate the cache, so the key includes the
-;; resolved `file-truename', not just the symlink path.
+;; The VC modeline cache keys on the file path and the `cj/modeline-vc-show-remote'
+;; flag only.  `file-truename' is deliberately NOT in the key: it would run on
+;; every redisplay (the mode-line rebuilds the key each render to check validity),
+;; and a moved symlink target is picked up at the next TTL refresh anyway, since
+;; `vc-backend' resolves the link fresh.  The per-render stat isn't worth it.
 
 ;;; Code:
 
 (require 'ert)
-(require 'cl-lib)
 
 (add-to-list 'load-path (expand-file-name "modules" user-emacs-directory))
 (require 'modeline-config)
 
-;;; Normal Cases
-
-(ert-deftest test-modeline-vc-cache-key-includes-truename ()
-  "Normal: the cache key includes the resolved truename of the file."
-  (let ((f (make-temp-file "cj-mlkey-")))
-    (unwind-protect
-        (should (member (file-truename f) (cj/modeline-vc-cache-key f)))
-      (delete-file f))))
-
-;;; Boundary Cases
-
-(ert-deftest test-modeline-vc-cache-key-changes-when-symlink-target-moves ()
-  "Boundary: re-pointing a symlink to a new target changes the cache key.
-The symlink path is identical both times; only its truename differs, so a
-key that ignored the truename would serve a stale VC backend."
-  (let* ((dir (make-temp-file "cj-mlkey-dir-" t))
-         (target-a (expand-file-name "a" dir))
-         (target-b (expand-file-name "b" dir))
-         (link (expand-file-name "link" dir)))
-    (unwind-protect
-        (progn
-          (write-region "" nil target-a)
-          (write-region "" nil target-b)
-          (make-symbolic-link target-a link)
-          (let ((key-a (cj/modeline-vc-cache-key link)))
-            (delete-file link)
-            (make-symbolic-link target-b link)
-            (let ((key-b (cj/modeline-vc-cache-key link)))
-              (should-not (equal key-a key-b)))))
-      (delete-directory dir t))))
+(ert-deftest test-modeline-vc-cache-key-is-file-and-show-remote ()
+  "Normal: the key is (FILE SHOW-REMOTE), with no per-render file-truename stat."
+  (let ((cj/modeline-vc-show-remote nil))
+    (should (equal (cj/modeline-vc-cache-key "/x/y.el") '("/x/y.el" nil)))))
+
+(ert-deftest test-modeline-vc-cache-key-tracks-show-remote ()
+  "Boundary: toggling show-remote yields a different key (separate cache entry)."
+  (should-not (equal (let ((cj/modeline-vc-show-remote nil))
+                       (cj/modeline-vc-cache-key "/x/y.el"))
+                     (let ((cj/modeline-vc-show-remote t))
+                       (cj/modeline-vc-cache-key "/x/y.el")))))
 
 (ert-deftest test-modeline-vc-cache-key-stable-for-same-file ()
-  "Boundary: the key is stable across calls for an unchanged file."
-  (let ((f (make-temp-file "cj-mlkey-stable-")))
-    (unwind-protect
-        (should (equal (cj/modeline-vc-cache-key f)
-                       (cj/modeline-vc-cache-key f)))
-      (delete-file f))))
+  "Boundary: the key is stable across calls for an unchanged file + show-remote."
+  (let ((cj/modeline-vc-show-remote nil))
+    (should (equal (cj/modeline-vc-cache-key "/x/y.el")
+                   (cj/modeline-vc-cache-key "/x/y.el")))))
 
 (provide 'test-modeline-config-vc-cache-key)
 ;;; test-modeline-config-vc-cache-key.el ends here
diff --git a/tests/test-modeline-config-vc-cache.el b/tests/test-modeline-config-vc-cache.el
index b6aafbfbe..dab755442 100644
--- a/tests/test-modeline-config-vc-cache.el
+++ b/tests/test-modeline-config-vc-cache.el
@@ -98,5 +98,12 @@
       (should (text-property-any 0 (length rendered)
                                  'mouse-face 'mode-line-highlight rendered)))))
 
+(ert-deftest test-modeline-config-vc-fetch-swallows-vc-errors ()
+  "Error: a signal from the VC backend is swallowed (returns nil) rather than
+propagating into the mode-line redisplay path, where it would break all redisplay."
+  (cl-letf (((symbol-function 'file-remote-p) (lambda (&rest _) nil))
+            ((symbol-function 'vc-backend) (lambda (&rest _) (error "git boom"))))
+    (should (null (cj/modeline-vc-fetch "/tmp/project/file.el")))))
+
 (provide 'test-modeline-config-vc-cache)
 ;;; test-modeline-config-vc-cache.el ends here