uibinder/safehtml disagreement on xlink:href attribute

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Stephen Haberman

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Nov 18, 2015, 9:49:03 AM11/18/15

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I'm attempting to use icons in an svg file in a ui.xml file like:

But with a variable, so:

However, because of the xlink namespace (which the browser requires, AFAICT), UiBinder and SafeHtml end up disagreeing on whether this is a SafeUri-requiring attribute.

E.g. here is the UiBinder logic, which ignores namespace because it uses local name:

https://github.com/gwtproject/gwt/blob/master/user/src/com/google/gwt/uibinder/elementparsers/HtmlInterpreter.java#L48

And here is the SafeHtml logic, which does looks at namespace+attribute due to the underlying jsilver implementation:

https://github.com/gwtproject/gwt/blob/master/user/src/com/google/gwt/safehtml/rebind/SafeHtmlTemplatesImplMethodCreator.java#L301

https://code.google.com/p/jsilver/source/browse/trunk/src/com/google/streamhtmlparser/impl/HtmlParserImpl.java#237

So, it ends up failing because UiBinder generated SafeUri, but SafeHtml says "this attribute shouldn't be a SafeUri, did you SafeHtml or String".

I'm wondering how to make them agree...while in this scenario it is true that xlink:href is a URI, so UiBinder was right, in theory there could be other namespaces where that is not the case, and the heuristic of "any attribute named href is a uri, regardless of namespace" could be wrong.

Any great ideas?

...I suppose the other option is to just turn off safe html templates for now.

- Stephen

Thomas Broyer

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Nov 19, 2015, 5:28:21 AM11/19/15

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Well, three things:

There's an impedance mismatch between UiBinder (using XML with namespaces) and HTML. UiBinder has not been designed to output "namespaced HTML", and actually there's no such thing as "namespaced HTML" (SVG-in-HTML hardcodes the "xlink:href" name to translate to an "href" attribute in the XLink namespace in the InfoSet: https://html.spec.whatwg.org/multipage/syntax.html#adjust-foreign-attributes). To have UiBinder play well in those cases, it'd have to somehow follow the "InfoSet to HTML syntax" rules: https://html.spec.whatwg.org/multipage/syntax.html#serialising-html-fragments
UiBinder should probably converge to use jsilver's HtmlUtils.isAttributeUri and co. so we at least have the same rule everywhere.
JSilver should adjust to those special cases like "xhtml:href", and UiBinder should pass the appropriate name to JSilver (following the same "InfoSet to HTML syntax" mapping rules).