XMLDecl parent and next_sibling methods do not work

[henrik]

For documents with an explicit XML declaration, the parent and next_sibling methods do not work. (It is possible to locate the XML declaration using previous_sibling from the root element.)

This is a problem for programs that use treewalkers or node iterators, like the Test::Unit::Xml framework. The treewalker cannot walk the document tree because it gets stuck on the XML declaration.

The problem is serious because XML declarations are common, and mandatory in XML 1.1.

[henrik]

Unit test that fails because of the XML declaration bug

[ser]

Fixed by changeset:1277.

Note that the unit test had to be modified a bit, because the source document contains whitespace text nodes. Text nodes are siblings, so that

    assert_kind_of(REXML::XMLDecl, @root.previous_sibling)
    assert_kind_of(REXML::Element, @xml_declaration.next_sibling)

had to become:

    assert_kind_of(REXML::XMLDecl, @root.previous_sibling.previous_sibling)
    assert_kind_of(REXML::Element, @xml_declaration.next_sibling.next_sibling)

The other thing I could have done was told the parser to ignore whitespace. 6 of one, half-dozen of the other.