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Re: contemporary XML parsing in JavaScript

• From: Michael Kay <mike@saxonica.com>
• To: "Liam R. E. Quin" <liam@fromoldbooks.org>
• Date: Fri, 2 Dec 2022 08:46:28 +0000

The situation with XML parsing in Javascript is pretty dire. There are a lot of products that claim to be XML parsers but are poorly documented, only do the parts of XML that they fancy, and add in bits of HTML parsing where they feel like it. We have yet to find a parser that does DTD processing. The XXE security scare stories don't help, of course.

I don't think NPM downloads is a particularly good metric, because so many of them are from automated build scripts. It would be good to have a number for distinct IP addresses. For the record, SaxonJS is getting about 12K downloads per week, which is healthy, but a tiny fraction of these numbers.

The sax-js parser, which we use in Saxon, gets 28M downloads a week, far more than fast-xml-parser. And none of them are attributable to us, because we actually forked the code to fix some conformance bugs and ship a modified version. (We didn't contribute the changes back because some of them would cause compatibility problems by disabling non-conformant extensions.)

Michael Kay
Saxonica

> On 2 Dec 2022, at 05:56, Liam R. E. Quin <liam@fromoldbooks.org> wrote:
> 
> On Thu, 2022-12-01 at 16:25 -0500, Simon St.Laurent wrote:
>> 
>> "fast-XML-parser NPM package has more downloads/week (6 million) than
>> Vue (3.4 million) or Angular (3 million)."
> 
> Good fined!
> 
> 
> It might also suggest they do a lot of bug fixes, since node checks
> often for new revisions. Or that there was a mistake that caused the
> package to be downloaded every time node.js was started. Or that it's
> fairly widely used :)
> 
> Checking
> https://snyk.io/advisor/npm-package/fast-xml-parser
> i see that 658 other projects depend on it. Also, i do notice a spike
> of downloads after each release, but it's small compared to the total,
> so that's not a major factor.
> 
> React.js gets nearly 17 million downloads per week, though, accordingto
> that page, and xml-js gets over 14.
> 
> It's not a validating parser; the documentation says "DOCTYPE entities
> are supported" and also "unpaired tags (Eg <br> in HTML), stop nodes
> (Eg <script> in HTML) are supported"
> See https://github.com/NaturalIntelligence/fast-xml-parser
> 
> 
> The "validator" has an option, "allowBooleanAttributes" but doesn't
> seem to have any reference to a DTD or external document type
> definition: it's checking well-formedness:
> 
>   const xmlData = `<parent><extra></parent>`;
>   const result = XMLValidator.validate( xmlData, {
>     unpairedTags: ["extra"]
>   });
> 
> Being able to "validate" this as XML is a violation of the XML
> specification, but that doesn't mean it isn't useful.
> 
> The parser does not allow entity replacement text to contain &, and
> also goes wrong (silently returns an incorrect result as XML) if there
> is an unescaped & in the input.
> 
> So, it's moderately popular, widely used, a little buggy...
> interestingly, it has some HTML entities built in such as &inr; for
> Indian Rupee but not egrave etc.
> 
> It looks like they are actively working to improve it, and are aware
> of, and admit to, its limitations, which is excellent.
> 
> liam
> 
> -- 
> Liam Quin, https://www.delightfulcomputing.com/
> Available for XML/Document/Information Architecture/XSLT/
> XSL/XQuery/Web/Text Processing/A11Y training, work & consulting.
> Barefoot Web-slave, antique illustrations:  http://www.fromoldbooks.org
> 
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• References:
  • contemporary XML parsing in JavaScript
    • From: "Simon St.Laurent" <simonstl@simonstl.com>
  • Re: contemporary XML parsing in JavaScript
    • From: "Liam R. E. Quin" <liam@fromoldbooks.org>