Saxon

It seems to me that an error https://www.w3.org/TR/xpath-30/#ERRXPDY0002 should be raised if the context item has been declared to be absent and there is use of a global variable (e.g. add_out-interface-usages) having an <xsl:copy> instruction inside . Let's see what Michael says.

Just clarifying my description above where the end of lines were swallowed:

java -jar /tmp/saxon9he.jar -s:datastore.xml -xsl:orig.xsl -o:orig_output.xml -t -T > orig_debug.log 2>&1

where orig_output.xml contains
<out-interface-usages>
<interface-usages>subtended-node-port</interface-usages>
</out-interface-usages>



java -jar /tmp/saxon9he.jar -s:datastore.xml -xsl:nocontext.xsl -o:nocontext_output.xml -t -T > nocontext_debug.log 2>&1

where nocontext_output.xml contains
<out-interface-usages/>



files.zip contains the following: 
saxonica_ticket/ 
├── datastore.xml 
├── nocontext_debug.log 
├── nocontext_output.xml 
├── nocontext.xsl 
├── orig_debug.log 
├── orig_output.xml 
├── orig.xsl 
└── README

The only difference is that nocontext.xsl contains <xsl:global-context-item use="absent"/>. As such, I would expect the output of the XSLT to be the same or a more graceful behaviour, with error or not.

The spec states in §11.9.1

[ERR XTTE0945] It is a type error to use the xsl:copy instruction with no select attribute when the context item is absent.

and Saxon is failing to report this error. Instead, xsl:copy is returning an empty sequence in this situation (i.e. it is a no-op).

In fact there are two opportunities to detect the type error, at compile time and at run time, and Saxon is missing both.

In XSLGlobalVariable.initializeBinding() it should check for the existence of an <xsl:global-context-item> declaration when allocating a static type to the contextItemStaticInfo object.

In Copy.processLeavingTail it should report a type error if the context item is null.

Thanks for the prompt response. It will help us in improving our XSL to prevent these issues to start with.

Leaving bug as resolved until fix applied to the Saxon 10 maintenance release.