[libvirt PATCH v5 0/8] Refactor XML parsing boilerplate code

[Tim Wiederhake]

polite ping

On Thu, 2021-04-08 at 13:19 +0200, Tim Wiederhake wrote:
> This series lays the groundwork for replacing some recurring
> boilerplate code
> in src/conf/ regarding the extraction of XML attribute values.
> 
> For an on / off attribute, the boilerplate code looks roughly like
> this,
> 
>   g_autofree char *str = NULL;
>   if (str = virXMLPropString(node, "x")) {
>     int val;
>     if ((val = virTristateBoolTypeFromString(str)) <= 0) {
>       virReportError(...)
>       return -1;
>     }
>     def->x = val;
>   }
> 
> with some variations regarding how `str` is free'd in case of later
> re-use,
> the exact error message for invalid values, whether or not
> `VIR_TRISTATE_(SWITCH|BOOL)_ABSENT` is explicitly checked for (`val <
> 0` vs.
> `val <= 0`), whether an intermediate variable is used or the value is
> assigned
> directly, and in some cases the conditions in the two if-blocks are
> merged.
> 
> After the refactoring, the above code block looks like this:
> 
>   if (virXMLPropTristateBool(node, "x", VIR_XML_PROP_OPTIONAL, &def-
> >x) < 0)
>       return -1;
> 
> Similar functions are introduced for integer valued attributes,
> unsigned
> integer valued attributes and enum valued attributes.
> 
> Patches #6, #7, and #8 demonstrate the application of these function
> and stand
> representative of more patches that I did not sent along yet as to
> not drown
> the mailing list in spam. These patches remove a total of ~ 1000
> lines of code
> and fix some places, where e.g. `<foo bar="default"/>` would
> incorrectly be
> accepted as virXMLTristateBool.
> 
> As an added benefit, this refactoring makes the error messages for
> invalid
> values in these XML attributes much more consistent:
> 
>   $ git diff master | grep "^-.*_(\"" | wc -l
>   239
>   $ git diff master | grep "^+.*_(\"" | wc -l
>   21
> 
> V1: 
> https://listman.redhat.com/archives/libvir-list/2021-March/msg00853.html
> V2: 
> https://listman.redhat.com/archives/libvir-list/2021-March/msg00994.html
> V3: 
> https://listman.redhat.com/archives/libvir-list/2021-March/msg01066.html
> V4: 
> https://listman.redhat.com/archives/libvir-list/2021-April/msg00209.html
> 
> Changes since V4:
> * Added custom error message for virXMLProp(Int|UInt) when the
> attribute value
>   is 0 and VIR_XML_PROP_NONZERO is specified.
> 
> Cheers,
> Tim
> 
> Tim Wiederhake (8):
>   virxml: Add virXMLPropTristateBool
>   virxml: Add virXMLPropTristateSwitch
>   virxml: Add virXMLPropInt
>   virxml: Add virXMLPropUInt
>   virxml: Add virXMLPropEnum
>   virNetworkForwardNatDefParseXML: Use virXMLProp*
>   virDomainIOThreadIDDefParseXML: Use virXMLProp*
>   virCPUDefParseXML: Use virXMLProp*
> 
>  src/conf/cpu_conf.c      |  14 +-
>  src/conf/domain_conf.c   |  14 +-
>  src/conf/network_conf.c  |  16 +--
>  src/libvirt_private.syms |   5 +
>  src/util/virxml.c        | 267
> +++++++++++++++++++++++++++++++++++++++
>  src/util/virxml.h        |  31 +++++
>  6 files changed, 312 insertions(+), 35 deletions(-)
> 
> -- 
> 2.26.2
> 
>