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Diffstat (limited to 'working/org-element-cache-persist-bug/upstream-report.txt')
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1 files changed, 87 insertions, 0 deletions
diff --git a/working/org-element-cache-persist-bug/upstream-report.txt b/working/org-element-cache-persist-bug/upstream-report.txt new file mode 100644 index 00000000..81fcaaa7 --- /dev/null +++ b/working/org-element-cache-persist-bug/upstream-report.txt @@ -0,0 +1,87 @@ +Subject: [BUG] Persisting the element cache while its buffer is live corrupts it [9.7.11 (release_9.7.11 @ /usr/share/emacs/30.2/lisp/org/)] + +Writing the element cache to disk strips the :buffer property from every cached +element in the live buffer and never puts it back. The next access to a cached +headline signals (wrong-type-argument stringp nil), and it keeps signalling until +the cache is reset by hand. + +Minimal reproduction, self-contained, no dirvish or other packages involved. Save +as repro.el and run "emacs -Q --batch -l repro.el": + + (require 'org) + (require 'org-element) + (require 'org-persist) + + (let* ((dir (make-temp-file "org-persist-repro-" t)) + (org-persist-directory (expand-file-name "persist" dir)) + (file (expand-file-name "notes.org" dir)) + (org-element-use-cache t) + (org-element-cache-persistent t) + (org-log-done nil)) + (with-temp-file file + (dotimes (i 20) (insert (format "* TODO task %d\nbody %d\n" i i)))) + (let ((buffer (find-file-noselect file))) + (with-current-buffer buffer + (org-element-cache-reset) + (org-element-cache-map #'ignore :granularity 'headline) + (goto-char (point-min)) + (re-search-forward "^\\* TODO task 0") + (beginning-of-line) + (org-todo "DONE")) + (org-persist-write `((elisp org-element--cache) + (version ,org-element-cache-version)) + buffer t) + (with-current-buffer buffer + (message "%S" + (condition-case err + (progn (org-element-cache-map + (lambda (e) (org-element-property :raw-value e)) + :granularity 'headline) + "ok") + (error err)))) + (set-buffer-modified-p nil) + (kill-buffer buffer)) + (delete-directory dir t)) + +Expected: "ok". +Actual: (wrong-type-argument stringp nil). + +Adding a print of the cached :buffer values on either side of the write shows +(#<buffer notes.org>) before and (nil) after. + +The mechanism, as far as I can follow it. org-element--cache-persist-before-write +walks org-element--cache and clears :buffer on every element. That looks +deliberate, since buffer objects can't be printed, and a8286a5a9 describes it as +"Clear and restore non-printable buffer objects in :buffer property". The restore +half is org-element--cache-persist-after-read, which sets :buffer back to +(current-buffer). But that only runs on the read path. Nothing restores :buffer +after a write, so a write against a buffer that is still alive leaves the live +cache holding nils. + +The error itself comes from org-element--headline-parse-title. Cached elements +keep their deferred :title and :tags thunks, and resolving one runs +(with-current-buffer (org-element-property :buffer headline)). set-buffer on nil +is the signal. + +How I reached it without calling org-persist-write directly. Any second buffer +visiting the same file will do it, because org-persist registers a buffer-local +org-persist-write-all-buffer on kill-buffer-hook, and the write's hook resolves +(get-file-buffer FILE), which can return the other buffer. In my case dirvish +built a preview buffer, pointed buffer-file-name at a file I already had open, +and ran set-auto-mode. Killing that preview corrupted the cache of the buffer I +was working in. Any package that makes a throwaway buffer visiting a live file +can trigger it, so I don't think this is dirvish's bug to fix. + +Two details that might help narrow it. Which buffer gets damaged depends on +buffer-list order, since get-file-buffer returns the first buffer visiting the +file. And a nearly empty cache survives, because the next access reparses instead +of reading a stripped element. That combination is probably why this shows up as +an intermittent "org-element cache is broken again" rather than a clean repro. + +Setting org-element-cache-persistent to nil avoids it, which I see recommended on +this list fairly often. It looks like it may be working around this rather than a +separate problem. + +I haven't written a patch. From the outside the symmetric fix would be to restore +:buffer after an in-session write the way the read path does, rather than to stop +clearing it. Happy to test a patch against the reproduction above. |