"Warning XSLT version ignored" output when using Jing with Saxon 11.4

[rdeltour]

When using Jing with Saxon 11.4, the following warning is reported (when using Schematron)

Warning
  XSLT version ignored: only "3.0" is recognized

This is due to Jing's Saxon factory setting the XSLT_VERSION feature to "2.0" (in NewSaxonSchemaReaderFactory), which is reported by Saxon (in the Configuration class).

I'm not quite sure since when Saxon reports that (probably since it implements XSLT 3.0).

The workaround I found in EPUBCheck (see w3c/epubcheck#1448) is to provide a custom SchematronSchemaReaderFactory via SPI, which does not set that feature.

I don't know how to best silence this warning in Jing, or if Jing should try to to not set that feature when detecting Saxon's XSLT 3.0 support. Any advice @ndw?

[ndw]

Let me give it some thought. Busy week and my brain is currently overfull.

[rdeltour]

Let me give it some thought. Busy week and my brain is currently overfull.

Of course, nothing pressing on my side! We have a workaround in EPUBCheck.

[michaelhkay]

At one time (before 3.0 was finalised) Saxon had the option to operate as either a 2.0 or a 3.0 conformant processor. If you selected 2.0 (in the API), then we tried hard to suppress all 3.0 features such as new functions, xsl:iterate, etc. Simply setting version="2.0" in the stylesheet doesn't have this effect (3.0 features will still work, so you don't pass the conformance tests for 2.0). At some later date we decided we would no longer have a 2.0-conformant mode: if you request 2.0, we fall back to 3.0, so you get the 3.0 features whether you like it or not. We made this decision because the level of backwards compatibility between 2.0 and 3.0 is very high, so pretty well all non-error stylesheets will run unchanged. If you ask for 2.0 conformance, we can't meet your request, so we give a warning that we are falling back to 3.0. I think that's reasonable.

More recently we've been going through all the warning messages making sure they all have unique error codes so it's easier to suppress them in an ErrorReporter. It looks like I missed this one: I'll fix that.

[rdeltour]

Thanks for the explanation @michaelhkay!

the level of backwards compatibility between 2.0 and 3.0 is very high, so pretty well all non-error stylesheets will run unchanged

so, can we safely assume that setting the "XSLT_VERSION" feature in Jing is effectively useless ? (or irrelevant even in Saxon versions which did have a 2.0-conformant mode?)

I'm trying to figure out if removing that configuration:

factory.setAttribute(FeatureKeys.XSLT_VERSION, "2.0");

would be a safe way to fix the issue on Jing's side, rather than asking users to suppress the warning in an ErrorReporter.

[michaelhkay]

Absolutely. The warning is telling you that there's no point setting the version to 2.0, because Saxon will use the default (3.0) regardless.

The only real point in requesting 2.0 would be to avoid accidentally using 3.0 features, in order to make sure that your code is portable to other 2.0 processors. But Saxon no longer provides that option.

[rdeltour]

Ok, thanks for confirming, @michaelhkay!