I find that a key() expression returns more nodes than it should.  The
expression is evaluated in the context of an exsl:node-set document.  The code
uses the same key with multiple exsl:node-set documents.

See my bug #148773 from about a year ago.  I got your fix for that from CVS and
had been using that version until yesterday when I upgraded to version 1.1.15
(Debian) and found this new issue.  I have just tried with the current CVS
version and it also fails.  So the regression occured between 2004-08-02 and 1.1.15.

I am still working on a minimal test case and will post something here when it
is narrowed down further, but for the time being here is an overview.  I am
hoping that perhaps you will immediately recognise the problem from this
description.

I have a key definition:

<xsl:key name="tree-by-subject_id" match="tree" use="@subject_id"/>

I perform transformations in a series of steps, using exsl:node-set and
variables to store the intermediate results:

<xsl:variable name="X">
  <xsl:apply-templates select="/" mode="step1"/>
</xsl:variable>

<xsl:variable name="Y">
  <xsl:apply-templates select="exsl:node-set($X)" mode="step2"/>
</xsl:variable>

<xsl:apply-templates select="exsl:node-set($Y)" mode="step3"/>


More than one of these steps makes use of the key in expressions like this:

<xsl:value-of select="count(key('tree-by-subject-id',$a))"/>

Generally the result will be 1, i.e. each subject_id attribute value will
identify a single tree node; this code is checking for duplicates.

With the new version of libxslt I find that this code is returning 2 in most
cases during one of the transformation steps.

If instead I write

<xsl:value-of select="count(//tree[@subject_id=$a])"/>

I still get 1 as before (but it evaluates more slowly).

I consider the fact that the key() expression returns a different result from
the //tree[] expression, which is just the key definition inlined, to be the
"smoking gun" that this is a library bug.

Looking at

<xsl:for-each select="key(...)">
  <xsl:value-of select="generate-id()">
</xsl:for-each>

and

<xsl:for-each select="//tree[...]">
  <xsl:value-of select="generate-id()">
</xsl:for-each>

I see that the key() returns the same node as the inline version of the
expression, plus one other node.

I will continue to work on a minimal example.

I have also upgraded libxml2, if that matters.

Regards,  --Phil.