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.

2 files changed, 123 insertions, 20 deletions

diff --git a/lisp/arc-mode.el b/lisp/arc-mode.el
index 5e696c091b2..0a971799746 100644
--- a/lisp/arc-mode.el
+++ b/lisp/arc-mode.el
@@ -645,6 +645,49 @@ Does not signal an error if optional argument NOERROR is non-nil."
       (if (not noerror)
           (error "Line does not describe a member of the archive")))))
 ;; -------------------------------------------------------------------------
+;;; Section: Helper functions for requiring filename extensions
+
+(defun archive--act-files (command files)
+  (lambda (archive)
+    (apply #'call-process (car command)
+           nil nil nil (append (cdr command) (cons archive files)))))
+
+(defun archive--need-rename-p (&optional archive)
+  (let ((archive
+         (file-name-nondirectory (or archive buffer-file-name))))
+    (cl-case archive-subtype
+      ((zip) (not (seq-contains-p archive ?. #'eq))))))
+
+(defun archive--ensure-extension (archive ensure-extension)
+  (if ensure-extension
+      (make-temp-name (expand-file-name (concat archive "_tmp.")))
+    archive))
+
+(defun archive--maybe-rename (newname need-rename-p)
+  ;; Operating with archive as current buffer, and protect
+  ;; `default-directory' from being modified in `rename-visited-file'.
+  (when need-rename-p
+    (let ((default-directory default-directory))
+      (rename-visited-file newname))))
+
+(defun archive--with-ensure-extension (archive proc-fn)
+  (let ((saved default-directory))
+    (with-current-buffer (find-buffer-visiting archive)
+      (let ((ensure-extension (archive--need-rename-p))
+            (default-directory saved))
+        (unwind-protect
+            ;; Some archive programs (like zip) expect filenames to
+            ;; have an extension, so if necessary, temporarily rename
+            ;; an extensionless file for write accesses.
+            (let ((archive (archive--ensure-extension
+                            archive ensure-extension)))
+              (archive--maybe-rename archive ensure-extension)
+              (let ((exitcode (funcall proc-fn archive)))
+                (or (zerop exitcode)
+                    (error "Updating was unsuccessful (%S)" exitcode))))
+          (progn (archive--maybe-rename archive ensure-extension)
+                 (revert-buffer nil t)))))))
+;; -------------------------------------------------------------------------
 ;;; Section: the mode definition
 
 ;;;###autoload
@@ -1378,16 +1421,9 @@ NEW-NAME."
 	  (setq ename
 		(encode-coding-string ename archive-file-name-coding-system))
           (let* ((coding-system-for-write 'no-conversion)
-		 (default-directory (file-name-as-directory archive-tmpdir))
-		 (exitcode (apply #'call-process
-				  (car command)
-				  nil
-				  nil
-				  nil
-				  (append (cdr command)
-					  (list archive ename)))))
-            (or (zerop exitcode)
-		(error "Updating was unsuccessful (%S)" exitcode))))
+                 (default-directory (file-name-as-directory archive-tmpdir)))
+            (archive--with-ensure-extension
+             archive (archive--act-files command (list ename)))))
       (archive-delete-local tmpfile))))
 
 (defun archive-write-file (&optional file)
@@ -1510,9 +1546,7 @@ as a relative change like \"g+rw\" as for chmod(2)."
 	  (archive-resummarize))
       (error "Setting group is not supported for this archive type"))))
 
-(defun archive-expunge ()
-  "Do the flagged deletions."
-  (interactive)
+(defun archive--expunge-maybe-force (force)
   (let (files)
     (save-excursion
       (goto-char archive-file-list-start)
@@ -1526,7 +1560,8 @@ as a relative change like \"g+rw\" as for chmod(2)."
     (and files
 	 (or (not archive-read-only)
 	     (error "Archive is read-only"))
-	 (or (yes-or-no-p (format "Really delete %d member%s? "
+         (or force
+             (yes-or-no-p (format "Really delete %d member%s? "
 				  (length files)
 				  (if (null (cdr files)) "" "s")))
 	     (error "Operation aborted"))
@@ -1540,13 +1575,14 @@ as a relative change like \"g+rw\" as for chmod(2)."
 	       (archive-resummarize)
 	     (revert-buffer))))))
 
+(defun archive-expunge ()
+  "Do the flagged deletions."
+  (interactive)
+  (archive--expunge-maybe-force nil))
+
 (defun archive-*-expunge (archive files command)
-  (apply #'call-process
-	 (car command)
-	 nil
-	 nil
-	 nil
-	 (append (cdr command) (cons archive files))))
+  (archive--with-ensure-extension
+   archive (archive--act-files command files)))
 
 (defun archive-rename-entry (newname)
   "Change the name associated with this entry in the archive file."
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