iyzsong@member.fsf.org (宋文武) skribis:

> ludo@gnu.org (Ludovic Courtès) writes:
>
>> [...]
>>
>>> I/O error : Permission denied
>>> I/O error : Permission denied
>>> Failed to write XML file; For permission problems, try rerunning as root
>>
>> I found that string comes from ‘shared-mime-info’, which is itself used
>> by the ‘xdg-mime-database’ hook in (guix profiles) (a hook that runs
>> when the profile is created to update the MIME database):
>>
>> static gboolean save_xml_file(xmlDocPtr doc, const gchar *filename, GError **error)
>> {
>> #if LIBXML_VERSION > 20400
>> 	if (xmlSaveFormatFileEnc(filename, doc, "utf-8", 1) < 0)
>> 	{
>> 		g_set_error(error, G_FILE_ERROR, G_FILE_ERROR_FAILED,
>> 			    "Failed to write XML file; For permission problems, try rerunning as root");
>> 		return FALSE;
>> 	}
>> #else
>>
>> 宋文武: any idea what the problem might be?  Perhaps
>> ‘update-mime-database’ is trying to write to /gnu/store/…-something?
> Yep, it happends when '$out/share/mime/application' is not writable.
> The xml files under 'application' are going to be generated by
> update-mime-database, and the shared-mime-info package has it
> pre-generated, so after union "share/mime", an un-writable 'application'
> directory point to the store will cause the problem.
>
> Commit 359f06aa fix this by union the "share/mime/packages" directory.

OK, thanks for the quick (brown?) fix!

>> Also, it’s a problem that ‘update-mime-database’ returns 0 here, as
>> seems to be the case.
> It returns 256 here for the problem, but the derivation still built and
> profile got updated, I have no idea about this :-
>
> Does a failing hook (returns #f) supposed to top the profile update?

I thought it did, but it doesn’t:

  (gexp->derivation "foo" #~(begin (mkdir #$output) #f))

leads a derivation that succeeds, contrary to
‘build-expression->derivation’.

To avoid that, we need an explicit (exit #f).

For now I prefer to address it at every call site (patch below) instead
of adding some magic to ‘gexp->derivation’, which would be hard to do in
a hygienic way.

Thanks,
Ludo’.