Saxon

The problem is actually in the Java code of ParseOptions.merge(). This code attempts to combine two sets of parser options (for example those set in the configuration file and those set on the document builder) by taking non-default values in preference to default values. However, for the ParserFeatures field, we're simply taking the union of the two sets of ParserFeatures, which in this case includes both http://xml.org/sax/features/validation=false and http://xml.org/sax/features/validation=true so the result is arbitrary.

Note that the problem manifests itself as a failure in NUnit test TestDocumentBuilder.TestSaxSourceValidation().

Confirmed that if we merge features in such a way that a "true" setting always overrides a "false" setting, the unit test now passes.

The code change applies to the 10.x, 11.x, and 12.x branches even though we have only seen adverse effects on the 10.x branch.