bug#24978: 25.1; Bad interaction between nxml-auto-insert-xml-declaration-flag and archive-extract

bug#24978: 25.1; Bad interaction between nxml-auto-insert-xml-declaration-flag and archive-extract

[Heinz Rommerskirchen]

If the variable nxml-auto-insert-xml-declaration-flag is set, an XML
declaration is inserted into non-empty XML files inside a zip archive.

To reproduce this bug create the valid XML file foo.xml containing
=== start foo.xml ===
<?xml version="1.0" encoding="utf-8"?>
<content>y</content>
=== end foo.xml ===
and pack it into a zip-archive:
$ zip -m bar.zip foo.xml
Now start "emacs -Q", evaluate
"(setq nxml-auto-insert-xml-declaration-flag 't)" in the *scratch*
buffer, visit bar.zip with C-x C-f, and press Enter on the entry
"foo.xml". foo.xml will be opened and an additional XML declaration is
inserted into the buffer rendering the file invalid and marking the
buffer as modified.

The following simple patch solved the problem for me.

=== start patch ====
--- nxml-mode-from-25.1.el	2016-11-20 19:45:43.339427354 +0100
+++ nxml-mode.el	2016-11-20 19:48:26.009625534 +0100
@@ -566,7 +566,8 @@
    ;; hook. The hook also had the drawback of overriding explicit user
    ;; instruction to save as some encoding other than utf-8.
    ;;(add-hook 'write-contents-hooks 'nxml-prepare-to-save)
-  (when (not (and (buffer-file-name) (file-exists-p (buffer-file-name))))
+  (when (and (not (and (buffer-file-name) (file-exists-p (buffer-file-name))))
+             (not archive-superior-buffer))
      (when (and nxml-default-buffer-file-coding-system
  	       (not (local-variable-p 'buffer-file-coding-system)))
        (setq buffer-file-coding-system nxml-default-buffer-file-coding-system))
=== end patch ===

-- 
Dr. Heinrich Rommerskirchen
Prof.-Schmid-Str. 41
82140 Olching
Allemagne

Tel. +49 8142 28787

Email heinz@h-rommerskirchen.de

bug#24978: 25.1; Bad interaction between nxml-auto-insert-xml-declaration-flag and archive-extract

[Lars Ingebrigtsen]

Heinz Rommerskirchen <heinz@h-rommerskirchen.de> writes:

> If the variable nxml-auto-insert-xml-declaration-flag is set, an XML
> declaration is inserted into non-empty XML files inside a zip archive.
>
> To reproduce this bug create the valid XML file foo.xml containing
> === start foo.xml ===
> <?xml version="1.0" encoding="utf-8"?>
> <content>y</content>
> === end foo.xml ===
> and pack it into a zip-archive:
> $ zip -m bar.zip foo.xml
> Now start "emacs -Q", evaluate
> "(setq nxml-auto-insert-xml-declaration-flag 't)" in the *scratch*
> buffer, visit bar.zip with C-x C-f, and press Enter on the entry
> "foo.xml". foo.xml will be opened and an additional XML declaration is
> inserted into the buffer rendering the file invalid and marking the
> buffer as modified.

(I'm going through older Emacs bug reports that have received no
response.)

I was able to reproduce the bug in Emacs 27, too.

> The following simple patch solved the problem for me.

[...]

> -  (when (not (and (buffer-file-name) (file-exists-p (buffer-file-name))))
> +  (when (and (not (and (buffer-file-name) (file-exists-p (buffer-file-name))))
> +             (not archive-superior-buffer))

Thanks for the patch, but I think the problem is a bit more general.
The intention seems to be to insert the declaration whenever you're
starting a new file, so I think a more general solution is to just check
whether the buffer is empty before inserting the declaration.  I've now
done this change on the Emacs trunk.

-- 
(domestic pets only, the antidote for overdose, milk.)
   bloggy blog: http://lars.ingebrigtsen.no