bug#40156: 26.3; append-to-file does not work on nonexistent file over ssh

[Michael Albinus <michael.albinus@gmx.de>]

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Version: 27.2

Sean Devlin <spd@toadstyle.org> writes:

> Hi folks,

Hi Sean,

> I did a little digging, and I think the problem is in
> tramp-sh-handle-write-region around line 3240:
>
>> 	  ;; If `append' is non-nil, we copy the file locally, and let
>> 	  ;; the native `write-region' implementation do the job.
>> 	  (when append (copy-file filename tmpfile 'ok))
>
> It looks like copy-file fails if filename doesn’t exist. Adding a test
> for file existence (i.e. file-exists-p) to the condition seems to
> solve the problem, though admittedly I only tested for my own narrow
> use case.

Thanks, and yes, your analysis is correct. I've committed a respective
patch to Emacs master. I've extended also tramp-tests.el
accordingly. The patch is appended.

Since Emacs 27.1 is already in pretest, I haven't applied it there. The
next Tramp release in GNU ELPA, 2.4.3.3, will contain the patch. It is
expected end of March.

> Thanks!

Best regards, Michael.


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diff --git a/lisp/net/tramp-sh.el b/lisp/net/tramp-sh.el
index 7ac41d16c8..06dca31227 100644
--- a/lisp/net/tramp-sh.el
+++ b/lisp/net/tramp-sh.el
@@ -3306,7 +3306,8 @@ tramp-sh-handle-write-region

 	  ;; If `append' is non-nil, we copy the file locally, and let
 	  ;; the native `write-region' implementation do the job.
-	  (when append (copy-file filename tmpfile 'ok))
+	  (when (and append (file-exists-p filename))
+	    (copy-file filename tmpfile 'ok))

 	  ;; We say `no-message' here because we don't want the
 	  ;; visited file modtime data to be clobbered from the temp
diff --git a/test/lisp/net/tramp-tests.el b/test/lisp/net/tramp-tests.el
index e220420d8c..e6c6b28c58 100644
--- a/test/lisp/net/tramp-tests.el
+++ b/test/lisp/net/tramp-tests.el
@@ -2356,7 +2356,14 @@ tramp-test10-write-region
 		(write-region nil nil tmp-name 3))
 	      (with-temp-buffer
 		(insert-file-contents tmp-name)
-		(should (string-equal (buffer-string) "foobaz"))))
+		(should (string-equal (buffer-string) "foobaz")))
+	      (delete-file tmp-name)
+	      (with-temp-buffer
+		(insert "foo")
+		(write-region nil nil tmp-name 'append))
+	      (with-temp-buffer
+		(insert-file-contents tmp-name)
+		(should (string-equal (buffer-string) "foo"))))

 	    ;; Write string.
 	    (write-region "foo" nil tmp-name)