Support for xs:assert and other XSD 1.1 features?

[DinoChiesa]

Apache XercesJ 2.12.2 supports XSD 1.1, which adds some handy features to XSD 1.0.

We can write a schema that supports xsd1.1 by including a minVersion attribute:

<xs:schema xmlns:xs="http://www.w3.org/2001/XMLSchema"
           xmlns:vc="http://www.w3.org/2007/XMLSchema-versioning"
           vc:minVersion="1.1"
           elementFormDefault="qualified">

Building a Java app that handles XSD 1.1 is pretty easy in code; you need to inspect the minVersion in the XSD file, then instantiate the schemaFactory appropriately, eg if 1.1, then

var schemaFactory = SchemaFactory.newInstance("http://www.w3.org/XML/XMLSchema/v1.1");
schemaFactory.setFeature(
        "http://apache.org/xml/features/validation/cta-full-xpath-checking", true);

(or just use 1.1 always, since it is a superset).

At runtime, though, there are a bunch of dependencies that are required to allow XSD 1.1 to work; these dependencies do not seem to be asserted in the POM file for XercesJ. Instead Apache bundles the dependencies in the "XSD1.1 ready" release of XercesJ. (tgz here)

The list of bundled dependencies is:

• cupv10k-runtime.jar
• icu4j.jar
• org.eclipse.wst.xml.xpath2.processor_1.2.1.jar
• resolver.jar
• serializer.jar
• xercesImpl.jar
• xml-apis.jar

Can this team build a lemminx that supports XSD 1.1 ?

[angelozerr]

Xerces doesn't provides XSD 1.1 on maven and if I remember I had some trouble with memory. See redhat-developer/vscode-xml#222

[DinoChiesa]

ahh I see you've been down this path before.

[DinoChiesa]

I tried to address that via this repo. Relying on that and jitpack.io, you can use

<project xsi:schemaLocation="http://maven.apache.org/POM/4.0.0 http://maven.apache.org/xsd/maven-4.0.0.xsd"
         xmlns="http://maven.apache.org/POM/4.0.0"
         xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance">
   ...
  <packaging>jar</packaging>
  ...
  <repositories>
    <repository>
      <!-- jitpack is a way to get dependencies from Github repos -->
      <id>jitpack.io</id>
      <url>https://jitpack.io</url>
    </repository>
  </repositories>

  <dependencies>
    <dependency>
      <groupId>com.github.DinoChiesa.xercesj-xsd11-package</groupId>
      <artifactId>xercesImpl-xsd11</artifactId>
      <version>20250630</version> <!-- release tag for this repo -->
      <!--
          <version>2.12.2</version>
      -->
    </dependency>
    ...

But , even after rebuilding lemminx on that new dependency, I ran into other runtime errors that were inscrutable. So I kinda gave up on doing XSD1.1 in Java with Xerces and fell back on a python-based implementation.