Improve handling of XML attributes and element values.

[blackwinter]

Make attribute markers configurable:

• Simple XML encoder
• Generic XML handler; see XML Attributes and Element values #379
• MARC21 XML handler; see MarcXmlEncoder ouputs "leader" wrongly #336

Make value tag names configurable:

• Simple XML encoder; see XML Attributes and Element values #379
• Generic XML handler

Fixes #379.

Related to #336.

[blackwinter]

We could also set DEFAULT_VALUE_TAG = "" and drop name.isEmpty().

[dr0i]

+1 simplify if you can ... did that as sideeffect of d9ba206.

[blackwinter]

This won't actually change the behaviour due to SimpleXmlEncoder.Element.writeElement(). But I think we should do it anyway, so we get our semantics straight.

[dr0i]

Thx, I think this is very nice!
I added a commit to reuse some variables, but I am not sure if this is good, especially the direct reference of DefaultXmlPipe in SimpleXmlEncoder. You may skip the commit (as we don't have an official contributing.md yet and we are the only one working on it you may use force push).

[blackwinter]

I added a commit to reuse some variables

I like the sentiment, thanks. But I see two issues with it:

1. You included the change with the empty literal names we discussed above. Was that intentional? I actually don't think that's such a good idea. I've pulled it out into a self-contained commit.
2. For compatibility reasons we can't set the default attribute marker for the handlers identical to the one in the encoder. That's just a minor nuisance, I guess.

as we don't have an official contributing.md yet

We don't? I thought that's what #375 was. How does it become official?

(Not that I mind, though... the rebase ban is one of my major grievances with these guidelines 😉)

[dr0i]

I added a commit to reuse some variables

I like the sentiment, thanks. But I see two issues with it:

1. You included the change with the empty literal names we discussed above. Was that intentional? I actually don't think that's such a good idea. I've pulled it out into a self-contained commit.

+1 right

2. For compatibility reasons we can't set the default attribute marker for the handlers identical to the one in the encoder. That's just a minor nuisance, I guess.

ack

as we don't have an official contributing.md yet

We don't? I thought that's what #375 was. How does it become official?

ups, right! Well maybe I had slumbering in my mind that you are not so fond of it ...

(Not that I mind, though... the rebase ban is one of my major grievances with these guidelines wink)

but we don't ban it at a whole ... might you want to read again https://github.com/metafacture/metafacture-core/blob/master/CONTRIBUTING.md#force-pushing and discuss your concerns (maybe via email)?