Handle modifications in extensionless zip files (bug#61326)

* lisp/arc-mode.el (archive-*-write-file-member)
(archive-*-expunge): Refactor to correctly modify
extensionless zip archives.
(archive-expunge): Move implementation to a separate helper
function to facilitate testing.
(archive--act-files): New helper function to wrap around
`call-process' calls.
(archive--need-rename-p): New helper function to check whether
a temporary rename is necessary.
(archive--ensure-extension) (archive--maybe-rename): New helper
functions to rename archive if the caller deems it necessary.
(archive--with-ensure-extension): New helper function to handle
writing an archive while ensuring extensionless archives work
correctly by temporarily renaming them.

* test/lisp/arc-mode-tests.el (arc-mode-test-zip-ensure-ext):
New regression test for bug#61326.

1 files changed, 67 insertions, 0 deletions

diff --git a/test/lisp/arc-mode-tests.el b/test/lisp/arc-mode-tests.el
index 32bce1b71bd..b6e06a563fe 100644
--- a/test/lisp/arc-mode-tests.el
+++ b/test/lisp/arc-mode-tests.el
@@ -46,6 +46,73 @@
       (when (buffer-live-p zip-buffer) (kill-buffer zip-buffer))
       (when (buffer-live-p gz-buffer) (kill-buffer gz-buffer)))))
 
+(ert-deftest arc-mode-test-zip-ensure-ext ()
+  "Regression test for bug#61326."
+  (skip-unless (executable-find "zip"))
+  (let* ((default-directory arc-mode-tests-data-directory)
+         (base-zip-1 "base-1.zip")
+         (base-zip-2 "base-2.zip")
+         (content-1 '("1" "2"))
+         (content-2 '("3" "4"))
+         (make-file (lambda (name)
+                      (with-temp-buffer
+                        (insert name)
+                        (write-file name))))
+         (make-zip
+          (lambda (zip files)
+            (delete-file zip nil)
+            (funcall (archive--act-files '("zip") files) zip)))
+         (update-fn
+          (lambda (zip-nonempty)
+            (with-current-buffer (find-file-noselect zip-nonempty)
+              (save-excursion
+                (goto-char archive-file-list-start)
+                (save-current-buffer
+                  (archive-extract)
+                  (save-excursion
+                    (goto-char (point-max))
+                    (insert ?a)
+                    (save-buffer))
+                  (kill-buffer (current-buffer)))
+                (archive-extract)
+                ;; [2] must be ?a; [3] must be (eobp)
+                (should (eq (char-after 2) ?a))
+                (should (eq (point-max) 3))))))
+         (delete-fn
+          (lambda (zip-nonempty)
+            (with-current-buffer (find-file-noselect zip-nonempty)
+              ;; mark delete and expunge first entry
+              (save-excursion
+                (goto-char archive-file-list-start)
+                (should (length= archive-files 2))
+                (archive-flag-deleted 1)
+                (archive--expunge-maybe-force t)
+                (should (length= archive-files 1))))))
+         (test-modify
+          (lambda (zip mod-fn)
+            (let ((zip-base (concat zip ".zip"))
+                  (tag (gensym)))
+              (copy-file base-zip-1 zip t)
+              (copy-file base-zip-2 zip-base t)
+              (file-has-changed-p zip tag)
+              (file-has-changed-p zip-base tag)
+              (funcall mod-fn zip)
+              (should-not (file-has-changed-p zip-base tag))
+              (should (file-has-changed-p zip tag))))))
+    ;; setup: make two zip files with different contents
+    (mapc make-file (append content-1 content-2))
+    (mapc (lambda (args) (apply make-zip args))
+          (list (list base-zip-1 content-1)
+                (list base-zip-2 content-2)))
+    ;; test 1: with "test-update" and "test-update.zip", update
+    ;; "test-update": (1) ensure only "test-update" is modified, (2)
+    ;; ensure the contents of the new member is expected.
+    (funcall test-modify "test-update" update-fn)
+    ;; test 2: with "test-delete" and "test-delete.zip", delete entry
+    ;; from "test-delete": (1) ensure only "test-delete" is modified,
+    ;; (2) ensure the file list is reduced as expected.
+    (funcall test-modify "test-delete" delete-fn)))
+
 (provide 'arc-mode-tests)
 
 ;;; arc-mode-tests.el ends here