index(register) from an XML source

[MF <massifr@fastwebnet.it>]

Hello list,
please see this:
----------------------------------------
\startbuffer[test]
<text>
  <div>
    <p>In this page there is a <name idref="id1">cat</name>,
      a <name idref="id2">dog</name>
     and a <name idref="id3">horse</name>.</p>
  </div>
  <div>
    <p>In this page there's only a <name idref="id2">fox
terrier</name>.</p>
  </div>
  <div>
    <p>In this page you find a <name idref="id1">persian cat</name>
     and a <name idref="id3">horse</name>.</p>
  </div>
  <index>
    <entry id="id1" data-sort="cat">Cat</entry>
    <entry id="id2" data-sort="dog">Dog</entry>
    <entry id="id3" data-sort="horse">Horse</entry>
  </index>
</text>
\stopbuffer

\defineregister[Animal][Animals]

\startxmlsetups xml:mysetup
  \xmlsetsetup{#1}{text|div|p|name|i|index|entry}{xml:*}
\stopxmlsetups

\xmlregistersetup{xml:mysetup}

\startxmlsetups xml:text
  \xmlflush{#1}
\stopxmlsetups

\startxmlsetups xml:div
  \xmlflush{#1}\page
\stopxmlsetups

\startxmlsetups xml:p
  \xmlflush{#1}\par
\stopxmlsetups

\startxmlsetups xml:name
 
\Animal[\xmlfunction{#1}{sortKeyOfAnimal}]{\xmlfunction{#1}{indexEntryF
orAnimal}}{\bf\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:i
  \dontleavehmode{\em\xmlflush{#1}}
\stopxmlsetups

\startxmlsetups xml:index
  \placeregister[Animal]
\stopxmlsetups

\startxmlsetups xml:entry
  \xmlflush{#1}
\stopxmlsetups

\startluacode
userdata = userdata or {}
userdata.animals = {}

function userdata.findAnimal(t)
  local idref = xml.attribute(t, "", "idref")
  local animal = userdata.animals[idref]
  if not animal then
    local entry = xml.first(t, "ancestor::text//index/entry[@id = '" ..
idref .. "']")
    local sortkey = xml.attribute(entry, "", "data-sort")
    animal = {}
    if sortkey and entry then
      animal.id = idref
      animal.sortkey = sortkey
      animal.entry = entry
      userdata.animals[idref] = animal
    end
  end
  return animal
end

function xml.functions.sortKeyOfAnimal(t)
  local animal = userdata.findAnimal(t)
  if animal.sortkey then
    context(animal.sortkey)
  else
    context("zzz")
  end
end

function xml.functions.indexEntryForAnimal(t)
  local animal = userdata.findAnimal(t)
  if animal.entry then
    lxml.flush(animal.entry)
  end
end
\stopluacode

\starttext
  \xmlprocessbuffer{main}{test}{}
\stoptext
----------------------------------------

It's a simplified version of the documents I'm working on:
- it's XML
- the index entries are already defined
- the entries of the index have an "id" attribute and they are
referred in the main text with an "idref" attribute
- \Animal[sortkey]{entry} is used to index the terms in the text
- "sortkey" and "entry" are calculated by the Lua code, that reads the
idref and finds the right entry inside the <index> element (it also
caches the entries)

Context has no problems with that code, but the index I get (page 4) is
something like this:

c
Cat 1
Cat 3

d
Dog 1
Dog 2

h
Horse 1
Horse 3

What I'd expect is instead:

c
Cat 1,3

d
Dog 1,2

h
Horse 1,3

Could you explain me why everytime I get a distinct entry in the index,
even when the sort key and the entry are the same? (or I only think
they are, but they are not really)
Thanks in advance,
Massi
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