HTML reader with auto_identifiers produces duplicate attributes

[bpj]

(See also pandoc-discuss)

When converting to mediawiki MW headings are prepended with a span
<span id="HEADING-ID"></span>, evidently to provide an anchor to
pandoc's original/automatic id so that internal links will still work. However
if there is a <section> element¹ I frequently end up with an identical id
tag on the div resulting from the section element and the automatically
inserted span element, which seems like a bug to me:

<section id="head-2" class="level2">
<h2>Head 2</h2>
<section id="head-3" class="level3">
<h3>Head 3</h3>
<ol type="1">
<li><p>Li 1</p></li>
<li><p>Li 2</p>
<p>Li 2 para 2</p></li>
<li><p>Li 3</p></li>
</ol>
<p>Text</p>
<ol type="i">
<li>Li i</li>
<li>Li ii</li>
</ol>
</section>
</section>

<div id="head-2" class="section level2">

<span id="head-2"></span>
== Head 2 ==

<div id="head-3" class="section level3">

<span id="head-3"></span>
=== Head 3 ===

<ol style="list-style-type: decimal;">
<li><p>Li 1</p></li>
<li><p>Li 2</p>
<p>Li 2 para 2</p></li>
<li><p>Li 3</p></li></ol>

Text

<ol style="list-style-type: lower-roman;">
<li>Li i</li>
<li>Li ii</li></ol>


</div>

</div>

It seems that the only fix currently is to go through the MW source after
conversion and manually remove any offending spans.

Footnotes

1. In my case inserted by pandoc into the HTML now used as source at an
   earlier run. ↩

[jgm]

Re-opening so we can add the section divs again, and just fix the id issue.

[jgm]

I reverted the change. Actually, it appears that the real issue is in the HTML reader. Using pandoc -f html -t native on the snippet above, we get:

[ Div
    ( "head-2" , [ "section" , "level2" ] , [] )
    [ Header
        2 ( "head-2" , [] , [] ) [ Str "Head" , Space , Str "2" ]
    , Div
        ( "head-3" , [ "section" , "level3" ] , [] )
        [ Header
            3 ( "head-3" , [] , [] ) [ Str "Head" , Space , Str "3" ]
...

So the problem here is that the HTML reader is adding auto-identifiers to the Header elements that duplicate the identifiers already present in the Divs. That is what needs fixing.

This also points to a workaround for your case: use -f html-auto_identifiers -t mediawiki.

[jgm]

With changes to the HTML reader, I now get:

<div id="head-2" class="section level2">

<span id="head-2-1"></span>
== Head 2 ==

<div id="head-3" class="section level3">

<span id="head-3-1"></span>
=== Head 3 ===

<ol style="list-style-type: decimal;">
<li><p>Li 1</p></li>
<li><p>Li 2</p>
<p>Li 2 para 2</p></li>
<li><p>Li 3</p></li></ol>

Text

<ol style="list-style-type: lower-roman;">
<li>Li i</li>
<li>Li ii</li></ol>


</div>

</div>

[jgm]

OK, those changes led to some other problems, e.g. with the LaTeX writer, so reverting for now.

[jgm]

What we really need is a pass through the AST at the end of the HTML writer that finds section Divs immediately containing a Header with the same id, and removes the id on the Header.