[PATCH for 7.4.0] conf: Avoid double indentation of <metadata/> element
Daniel P. Berrangé
berrange at redhat.com
Tue May 25 08:47:21 UTC 2021
On Tue, May 25, 2021 at 09:32:35AM +0200, Michal Privoznik wrote:
> There was a recent change in libxml2 that caused a trouble for
> us. To us, <metadata/> in domain or network XMLs are just opaque
> value where management application can store whatever data it
> finds fit. At XML parser/formatter level, we just make a copy of
> the element during parsing and then format it back. For
> formatting we use xmlNodeDump() which allows caller to specify
> level of indentation. Previously, the indentation was not
> applied onto the very first line, but as of v2.9.12-2-g85b1792e
> libxml2 is applying indentation also on the first line.
>
> This does not work well with out virBuffer because as soon as we
> call virBufferAsprintf() to append <metadata/> element,
> virBufferAsprintf() will apply another level of indentation.
>
> Instead of version checking, let's skip any indentation added by
> libxml2 before virBufferAsprintf() is called.
>
> Note, the problem is only when telling xmlNodeDump() to use
> indentation, i.e. level argument is not zero. Therefore,
> virXMLNodeToString() which also calls xmlNodeDump() is safe as it
> passes zero.
>
> Signed-off-by: Michal Privoznik <mprivozn at redhat.com>
> ---
>
> I've raised this issue with libxml2 team:
>
> https://gitlab.gnome.org/GNOME/libxml2/-/commit/85b1792e37b131e7a51af98a37f92472e8de5f3f
>
> but I'm not sure it'll be fixed. Unfortunately, the patch that's causing
> us trouble is being backported all over the place, because it's
> supposedly fixing a regression.
>
> src/conf/domain_conf.c | 9 ++++++++-
> src/conf/network_conf.c | 9 ++++++++-
> 2 files changed, 16 insertions(+), 2 deletions(-)
>
> diff --git a/src/conf/domain_conf.c b/src/conf/domain_conf.c
> index 4f78b7b43d..84a8c269be 100644
> --- a/src/conf/domain_conf.c
> +++ b/src/conf/domain_conf.c
> @@ -27808,6 +27808,7 @@ virDomainDefFormatInternalSetRootName(virDomainDef *def,
>
> if (def->metadata) {
> g_autoptr(xmlBuffer) xmlbuf = NULL;
> + const char *xmlbufContent = NULL;
> int oldIndentTreeOutput = xmlIndentTreeOutput;
>
> /* Indentation on output requires that we previously set
> @@ -27824,7 +27825,13 @@ virDomainDefFormatInternalSetRootName(virDomainDef *def,
> xmlIndentTreeOutput = oldIndentTreeOutput;
> return -1;
> }
> - virBufferAsprintf(buf, "%s\n", (char *) xmlBufferContent(xmlbuf));
> +
> + /* After libxml2-v2.9.12-2-g85b1792e even the first line is indented.
> + * But virBufferAsprintf() also adds indentation. Skip one of them. */
> + xmlbufContent = (const char *) xmlBufferContent(xmlbuf);
> + virSkipSpaces(&xmlbufContent);
> +
> + virBufferAsprintf(buf, "%s\n", xmlbufContent);
Won't this mean that indent is now wrong for the older libxml ?
Regards,
Daniel
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