[XML-SIG] Minidom bugs/questions
Sun, 04 Feb 2001 21:46:35 -0700
> > Converting my app to use minidom was easy enough, but I found out a
> > bout a bunch of differences between the two DOM implementations. Some
> > of these are fine with me (e.g. minidom doesn't preserve comments,
> > doesn't prefix its output with "<?xml version="1.0" ?>" when writing
> > XML output,
minidom should be fixed to put out an XML declaration, preferably with the
encoding. This is hardly a burden, and is *highly* recommended XML practice.
> > minidom returns Unicode strings even for ASCII input).
> > 1. The other DOM has a hasAttributes() predicate; minidom is missing
> > this and I have to use the more expensive form "if node.attributes".
> Right; that's a bug in minidom: hasAttributes was introduced in "DOM
> Level 2".
> The original idea of minidom was that it should be "minimal"; clearly
> that has not worked out, so we probably should review it carefully to
> achieve completeness (with respect to "DOM 2 Core").
Well, we should think about exactly what makes minidom "mini". It's debatable
whether it is possible to implement all of DOM Level 2 core and still be
"mini". And what about DOm level 3?
> > 4. In minidom, createDocument() leaves doc.documentElement set to None;
> > in the other DOM, doc.documentElement is initialized to an Element
> > node created from the second argument to createDocument(). (Again,
> > according to Fred, the DOM standard requires the latter.)
> That was a surprise to me. After reading the spec and a number of
> implementations, I think the requirement is much stronger: You MUST
> pass a qualifiedName, only the namespaceURI and the doctype are
Yes. This is a pain, but it is clearly fundamental to the DOM WG conceptual
> It appears to be a common trick to allow null in createDocument, so
> that the first element found during parsing can be introduced with
> appendChild, but that appears to be non-conforming (somebody please
> correct me if it is).
I think it is, even though 4DOM does this. Mike or Jeremy will probably
remind me if I'm missing something. From what I see of the readers, we don't
need this convenience.
> I could try to come up with a separate patch for that issue.
> > 5. When writing XML output from a DOM tree that uses namespace
> > attributes, minidom doesn't insert the proper "xmlns:<tag>=<URI>"
> > attributes. The other DOM gets this right. (This is a bit tricky
> > to do, although I've figured a good way to do it which I'll gladly
> > donate to minidom if it's deemed useful.)
> Yes, that is certainly desirable; minidom should support namespaces
Of course if it isn't Level 2 compliant, it needn't do so. I wouldn't
consider it unreasonable to have minidom L1 only. If users want Level 2, they
install PyXML or other.
> > 6. When writing XML output from a DOM tree that has a default
> > namespace, minidom writes <:tag>...</:tag> instead of
> > <tag>...</tag> like the other DOM, and like I would have expected.
> Certainly a bug. When writing out namespace declarations, dealing with
> default default namespace is really tricky (e.g. when a tree that had
> a default namespace is extended with an element with no namespace).
Horrid bug. Those are invalid XML 1.0 NMTOKENS.
Uche Ogbuji Principal Consultant
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