On 12/07/2011 08:10 PM, Daniel Veillard wrote:
On Mon, Dec 05, 2011 at 02:48:30PM -0700, Eric Blake wrote:
According to the official XML specification [1], attributes can be specified with either ' or " (where the difference is that you can use '"' or '"' but must use """, and conversely for "'" or "'" vs. '''). But our code generation in src/conf prefers to output the '' notation, as it is easier to write C string literals for that style. Using a consistent style throughout libvirt will make it easier for users to copy-and-paste without wondering why we switch quoting styles mid-stream. [...] diff --git a/tests/xml2sexprdata/xml2sexpr-escape.xml b/tests/xml2sexprdata/xml2sexpr-escape.xml index 6eed578..bca2c81 100644 --- a/tests/xml2sexprdata/xml2sexpr-escape.xml +++ b/tests/xml2sexprdata/xml2sexpr-escape.xml @@ -5,7 +5,7 @@ <type>hvm</type> <kernel>/var/lib/xen/vmlinuz.2Dn2YT</kernel> <initrd>/var/lib/xen/initrd.img.0u-Vhq</initrd> - <cmdline> method=http://download.fedora.devel.redhat.com/pub/fedora/linux/core/test/5.91/x86_64/os&version="devel" </cmdline> + <cmdline> method=http://download.fedora.devel.redhat.com/pub/fedora/linux/core/test/5.91/x86_64/os&version="devel" </cmdline> <loader>/usr/lib/xen/boot/hvmloader</loader>
Actually I dislike for this kind of things. It's semantically equivalent, and I don't think we should try to enforce arbitrary requirements which are not needed. This is actually more confusing for people who do know the XML spec, "why isn't my example good" it actually is! The choice of quotes is on purpose to allow easy serialization when you have ' or " in an attribute value. Requiring the user to escape is kind of wrong IMHO.
But the fact that we _didn't_ have any ' or " in attribute values in all of the conversion is a testament to the fact that we don't want to choose attributes with quoting in the attribute value.
Also the automatic rule won't be able to distinguish " and " within attribute text content from those within element text content, and we certainly don't want to make a simili parser in perl or regexps. Also if someone uses an XML editor on one of our fragment it's very likely that the ' will be turned into " because the distinction is not part of the XML infoset (i.e. the amount of data an XML parser should report to the application) and the tool will serialize back using his own preferences, and that's just fine.
I think the inconvenients in that case are not worth the possible improvement.
One of the improvements, which I already have noticed since I wrote the patch, is that it is easier to search the rng files for a particular macro definition. That is, if you KNOW that a syntax-check rule enforced the style of <define name='blah'>...</define>, it is easier to see <ref name='blah'/> and search for the definition; whereas pre-patch, you could see <ref name='blah'/> but not know whether to search for name='blah' or name="blah" to find the counterpart <define>. Notice that my syntax-check is not documenting anything contrary to the user; that is, no where did I change documentation to suggest to the user that they must prefer '' over "". Rather it is just presenting a consistent interface (since 'virsh dumpxml dom' always outputs name='value', then the web pages that document how to interpret 'virsh dumpxml' output should also use name='value'). We could drop the changes to the tests directory, if you'd like (that is, use just patches 2 and 3 for the ease of rng searching and for the consistent documentation, but leaving the test directory as a way to prove that the quoting style doesn't matter). But if you're dead set against this series, I guess it won't hurt things to drop it (I can continue to do a regex search for name=['"]blah when looking for a <def name='blah'> counterpart in rng, which is particularly hard to type at a shell command line, but oh well). Any other opinions? -- Eric Blake eblake@redhat.com +1-919-301-3266 Libvirt virtualization library http://libvirt.org