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https://issues.apache.org/jira/browse/XALANJ-2493?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=12782185#action_12782185
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Henry Zongaro commented on XALANJ-2493:
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Hi, Martin.
I was just trying out your patch and was tripped up by the references to an
AssertionError constructor. Where is that class defined?
> BasisLibrary.nodeList2Iterator broken
> -------------------------------------
>
> Key: XALANJ-2493
> URL: https://issues.apache.org/jira/browse/XALANJ-2493
> Project: XalanJ2
> Issue Type: Bug
> Security Level: No security risk; visible to anyone(Ordinary problems in
> Xalan projects. Anybody can view the issue.)
> Components: XSLTC
> Affects Versions: The Latest Development Code
> Reporter: Martin von Gagern
> Attachments: XALANJ-2493_1.patch, XALANJ_2493_Test1.java
>
>
> The current implementation of nodeList2Iterator is broken, because it can not
> deal with attribute nodes. It relies on copyNodes which in turn tries to add
> attribute nodes as children of some top level node. Attributes don't live on
> the children axis, though, so this is against DOM and causes a DOM exception
> in the Xerces DOM implementation and probably most other implementations. The
> resulting HIERARCHY_REQUEST_ERR was noted e.g. in XALANJ-2424.
> Furthermore, the implementation is inefficient, because it manually copies
> each and every node from the source document to a new DTM to some new DTM.
> The time overhead for the copying as well as the memory overhead for the
> additional DOM can be avoided in cases where the nodes come from some input
> document, as opposed to a document completely loaded within some extension
> function.
> A comment in the related XALANJ-2425 suggests returning DTMIterator from
> extension functions and avoiding the re-import for those. I don't like this
> idea because it exposes a lot of Xalans internals to extension functions, and
> because the returned node list might be newly created, while at least some of
> thenodes might still be from the same document. So instead of special cases
> for the list type, I implemented special cases for every node of the list. If
> it is a proxy node of the same (Multi)DOM, we simply use its handle.
> If not, we add it to some w3c DOM and turn that into a DTM, pretty much like
> the current implementation does. However, I dropped copyNodes in favor of
> Document.importNode, to avoid code duplication and rely on supposedly more
> heavily tested code. I also added another level of elements, so that there is
> one such dummy node for every item of the source list, with always a single
> child or element. A few assertions help ensure this single child policy. This
> is especially important in the new implementation, because otherwise it would
> become difficult to get the proxied nodes and the newly DTMified nodes into
> correct order.
> Right now, the import of DOM nodes is only implemented for those nodes I
> expect to turn up in the DTM in pretty much the same form as they do in the
> w3c DOM. For all other nodes, an internal error is thrown. This especially
> concerns document fragment nodes. At least in w3c DOM, a document fragment
> can never be a child, so if DTM behaves the same, we would need to import
> document fragments seperately, or expand them to the list of their children
> instead. I'm not sure what correct behaviour would be here, so I'd rather
> throw an exception than implement wrong behaviour.
> I also noticed that
> org.apache.xml.dtm.ref.DTMManagerDefault.getDTMHandleFromNode would in theory
> provide an implementation for turning w3c nodes into DTM handles - exactly
> what we need here. That method seems to start importing from the topmost
> ancestor of a node, giving as much context as possible, in contrast to both
> current and my suggested XSLTC approach, which destroys ancestor references.
> That method also seems to employ caches in order to avoid importing a
> document repeatedly. Sadly, actually using that method throws a
> ClassCastException as it expects a DTM generate from a DOM source to be a
> DOM2DTM, which SAXImpl is not. A comment inside that method also indicates
> that future implementations might drop auto-importing and instead leave it to
> the caller to import a DOM if it hasn't been imported before.
> I left my own attempt at an nodeList2Iterator implementation using
> getDTMHandleFromNode in place, renamed to
> nodeList2IteratorUsingHandleFromNode and made private. So it's there, it even
> gets compiled, but it won't get used. If that method gets fixed in
> XSLTCDTMManager or its ancestor, then this method might be used instead,
> giving a much simpler and cleaner implementation. If some of my code would be
> useful for such an implementation as well, like the check for "is same DOM",
> feel free to copy or move my code to those classes as well.
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