LaTeX: fix mark-up when \DUrole is used with multiple classes

[jfbu]

Fix #12744

Relates

• more latex problems with references inside parsed-literal directive (\DUrole) #3207. It could have been opportunity then to use nested mark-up in output. I did not check probably using comma separated classes was there since origin. It may have evolved in Docutils after Sphinx had inherited it.

This may be in all rigor breaking but I doubt very much people have customized LaTeX via \DUrole for simultaneous classes (the PR changes nothing when there is only one class) and anyhow it was never documented as possible so far.

EDIT: when I say "breaking" I only mean by that that if someone for example has defined via \@namedef a LaTeX command \DUrolestd,std-ref (where both comma and hyphen are part of the name) then this styling command will not be executed anymore as now only \DUrolestd and \DUrolestd-ref will be (if and only if they exist). The PDF build will not be broken in any way. And anyhow I would be very surprised someone has actually done that!.

I rebased on tip of master now that master passes tests.

[jfbu]

For the record: I plunged into ancient Docutils history, and found out that the related changes happened in their projet at r5742 (Dec 1, 2008) with a syntax change such as

-\docutilsrolevery{\docutilsrolespecial{interpreted text}}
+\DUspan{very,special}{interpreted text}

and then r5862 (Jan 30, 2009) which removed \DUspan in favor of \DUrole with nested output (quite a few renamings inside this code chunk have happened since, keeping its same functionality):

-        self.body.append(r'\DUspan{%s}{' %','.join(classes))
+        for cls in classes:
+            self.body.append(r'\DUrole{%s}{' % cls)
+        self.context.append('}' * (len(classes)))

with an example syntax change such as

-  \DUspan{argA,argB,argC}{<content>}
+  \DUrole{argi}{\DUrole{argii}{\DUrole{arg-3}{<content>}}}

This all happened between their Release 0.5 (2008-06-25) and their Release 0.6 (2009-10-11).¹

Sphinx seems to have inherited the short-lived (never released) \DUspan syntax at our commit 5f6c38f in March 2009 (but this may come from earlier, because it is posterior to the commit date introducing \DUrole into Docutils, perhaps this is not date when revision was merged). But \DUspan was not modified into \DUrole until much later: at 6b36b31 (see this Jan 15, 2016 comment) and the behavior of Sphinx LaTeX writer was not modified then to create nested macros as in Docutils.

Footnotes

1. Due to a issue with git tags at Docutils, one gets only
   $ git tag --contains 472ada29b7
   0.14
   0.14rc1 ↩

[jfbu]

I have rebased manually. Once tests complete and I have checked again the diff I will squash merge.