Handling namespaces when parsing XML

[Jefidev]

Currently the namespace of an XML attributes is discarded
That could lead to undesirable behavior. Parsing the following XML :
readXML("\<Data xmlns:ns=\"http://trivial\"\>\<Field name=\"A\" ns:name=\"a\"\>\</Field\>\</Data\>");

Lead to that :
node: "Data"(["Field"( [], name="a")])

Only one of the two "name" attribute was kept.

Proposed solution
The namespace could be handled like this :
node: "Data"(["Field"( [], default = [(name, "a")])] ns = [(name, "A")])])

Or like this :
node: "Data"(["Field"( [], ("", "name") = "a", ("ns", "name") = "A"])

But there may be a more "Rascalest" way.
The "get" method provided by the XML module should also accept an optional parameter in order to precise the namespace required :
get(node, "name") => "a"
get(node, "name", "ns") => "A"

This allows us to search the attribute associated with the correct namespace and that doesn't break the backward compatibility of the get function.

[jurgenvinju]

The XML reader has a fullyQualify option which seems to work, but it has an issue:

rascal>n = readXML("\<Field xmlns:ns=\"http://trivial\" name=\"A\" ns:name=\"a\"\>\</Field\>",fullyQualify=true);
node: "Field"(
  [],
  ns:name="a",
  name="A",
  xmlns=("ns":"http://trivial"))

The ns:name is not syntactically correct, so we can not address it in Rascal code.

@DavyLandman we might:

1. allow : in escaped qualified names, like so: \ns:name
2. substitute the : for - like so: \ns-name

I prefer the latter since it does not require adapting the Rascal syntax, but it's not so nice as the : solution. @PaulKlint @tvdstorm should have an opinion about this too..

[jurgenvinju]

Ok:

1. adding : to escaped names would be ambiguous; see a::qualified::Name
2. a complex solution would add only : and reject :: from escaped names; this has too much impact in the grammar in my mind
3. adding . to the escaped names would be an option, but still a substitution is required in the XML reader.
4. so for now it seems substituting : for - will do the trick.