Epub chunking customization

[Martin Doucha <next_ghost@quick.cz>]

Hi,
I'm trying to generate Epub file with autogenerated ToC in a separate
chunk at a specific position. I've tried to follow the howto at
http://www.sagehill.net/docbookxsl/ChunkingCustomization.html to the
best of my ability but no matter what I do, xsltproc just prints lots
of I/O errors when I add customized <xsl:template name="chunk"> that
relies on <xsl:apply-imports/>. Here's the whole minimal stylesheet
that doesn't work. I want to add some content customizations as well
(those should replace the first import according to the howto) but
let's keep it simple. The imports and includes are adapted from
epub3/chunk.xsl. Including epub3/chunk.xsl itself instead makes no
difference.

> <?xml version='1.0'?>
> <xsl:stylesheet xmlns:xsl="http://www.w3.org/1999/XSL/Transform"; version="1.0">
> <xsl:import href="http://docbook.sourceforge.net/release/xsl-ns/current/epub3/docbook.xsl"/>
> <xsl:import href="http://docbook.sourceforge.net/release/xsl-ns/current/xhtml/chunk-common.xsl"/>
> <xsl:include href="http://docbook.sourceforge.net/release/xsl-ns/current/xhtml/chunk-code.xsl"/>
> <xsl:include href="http://docbook.sourceforge.net/release/xsl-ns/current/epub3/epub3-chunk-mods.xsl"/>
> 
> <xsl:param name="generate.toc">
> book      title
> </xsl:param>
> <xsl:param name="process.empty.source.toc" select="1"/>
> <xsl:param name="process.source.toc" select="1"/>
> 
> <xsl:template name="chunk">
>   <xsl:param name="node" select="."/>
>   <xsl:variable name="ret">
>     <xsl:choose>
>       <xsl:when test="local-name($node) = 'toc'">1</xsl:when>
>       <xsl:when test="local-name($node) = 'preface'">0</xsl:when>
>       <xsl:otherwise>
>         <xsl:apply-imports/>
>       </xsl:otherwise>
>     </xsl:choose>
>   </xsl:variable>
>   <xsl:message>
>     <xsl:text>Chunk test: </xsl:text>
>     <xsl:value-of select="local-name($node)"/>
>     <xsl:text> - </xsl:text>
>     <xsl:value-of select="$ret"/>
>   </xsl:message>
>   <xsl:value-of select="$ret"/>
> </xsl:template>
> </xsl:stylesheet>

Notice the <xsl:message> near the end. When I run the above file,
xsltproc prints this:

> xsltproc ../xsl/epub-chunk.xsl ../swarmwise.docbook >/dev/null
> Chunk test: book - 
> Chunk test: bookinfo - 
> Chunk test: title - 
> Chunk test: subtitle - 
> Chunk test: preface - 0
> Chunk test: highlights - 
> Chunk test: para - 
> Chunk test: para - 
> Chunk test: toc - 1
> Chunk test: preface - 0
> Chunk test: epigraph - 
> Chunk test: para - 
> Chunk test: para - 
> Chunk test: part - 
> Chunk test: title - 
> Chunk test: chapter - 
> Chunk test: title - 

And lots more lines like that with no return value. After that, it
starts printing what looks like chunk IDs instead of 0/1 return values:

> Note: namesp. add : added namespace before processing              Swarmwise
> Chunk test:  - 
> Chunk test: preface - 0
> Chunk test: preface - 0
> Chunk test: preface - 0
> Chunk test: book - book-idm139645148695504
> Chunk test: book - 
> Chunk test: book - 
> Chunk test: book - book-idm139645148695504
> Chunk test: preface - 0
> Chunk test: preface - 0
> Chunk test: preface - 0
> Chunk test: book - book-idm139645148695504
> Chunk test: book - 
> Chunk test: book - 
> Chunk test: book - book-idm139645148695504

And after that, the chunk test output includes even pieces of text
from the book itself instead of 0/1 return values - chapter titles,
section titles and even entire paragraphs converted into plain text
with no XML markup.

Here's what xsltproc prints when I comment out the <xsl:message> block:

> xsltproc ../xsl/epub-chunk.xsl ../swarmwise.docbook >/dev/null
> Note: namesp. add : added namespace before processing              Swarmwise
> Error preface is not a chunk!
> Writing OEBPS/ for preface(predmluva)
> I/O error : Is a directory
> I/O error : Is a directory
> runtime error: file file:///usr/share/sgml/docbook/xsl-ns-stylesheets/xhtml/chunker.xsl line 172 element document
> xsltDocumentElem: unable to save to OEBPS/
> Error preface is not a chunk!
> Writing OEBPS/ for preface
> I/O error : Is a directory
> I/O error : Is a directory
> runtime error: file file:///usr/share/sgml/docbook/xsl-ns-stylesheets/xhtml/chunker.xsl line 172 element document
> xsltDocumentElem: unable to save to OEBPS/
> Writing OEBPS/ for section(hejno-je-otevrene)
> I/O error : Is a directory
> I/O error : Is a directory
> runtime error: file file:///usr/share/sgml/docbook/xsl-ns-stylesheets/xhtml/chunker.xsl line 172 element document
> xsltDocumentElem: unable to save to OEBPS/

I'm using DocBook XSL NS Stylesheets 1.78.0 and xsltproc --version
prints this:
> Using libxml 20901, libxslt 10128 and libexslt 817
> xsltproc was compiled against libxml 20901, libxslt 10128 and libexslt 817
> libxslt 10128 was compiled against libxml 20901
> libexslt 817 was compiled against libxml 20901

I've also tried changing the imports according to xhtml/chunk.xsl (to
generate normal chunked XHTML instead of Epub) but that just gave me
slightly different error messages from xsltproc. When I import only
epub3/chunk.xsl and comment out the custom "chunk" template, I get
usable chunked Epub data with no error messages from xsltproc. What am
I missing?

Regards,
Martin Doucha