Double occurrences of names in Index with biblatex

Question

I use biblatex with indexing option; moreover, inside the text I have some names to index, with the usual \index{} command. Since I have the same authors in the bibliography and in the text, in the Index I find two occurrences of the same name, the first one coming from text, the second one from bibliography, for example:

Homer, 27, 45, 79
Homer, 107

But it's wrong and confusing. How can I unify the names occurrences?

A minimal example:

\documentclass{article}
\usepackage{fontspec}
\usepackage[style=philosophy-verbose,scauthors=true,classical=true,%
volumeformat=romansc,indexing]{biblatex}
\usepackage{filecontents}
\usepackage{imakeidx}
\indexsetup{othercode=\footnotesize}
\makeindex[intoc=true]
\begin{filecontents*}{\jobname.bib}
@book{strawson:1966,
  author         = {Peter Strawson},
  title          = {The Bounds of Sense},
  publisher      = {Routledge},
  location       = {London},
  year           = {1966},
}
\end{filecontents*}
\addbibresource{\jobname.bib}

\begin{document}
De nobis ipsis silemus\footcite{strawson:1966}: De re autem, quae agitur,
petimus, as Strawson\index{Strawson, Peter} told
\newpage
De nobis ipsis silemus: De re autem, quae agitur,
petimus, as Strawson\index{Strawson, Peter} told
\newpage
De nobis ipsis silemus\footcite{strawson:1966}: De re autem, quae agitur,
petimus, as Strawson told
\newpage
De nobis ipsis silemus
De nobis ipsis silemus: De re autem, quae agitur,
petimus, as Strawson\index{Strawson, Peter} told
\newpage
De nobis ipsis silemus\footcite{strawson:1966}: De re autem, quae agitur,
petimus, as Strawson told

\printbibliography
\printindex
\end{document}

where you'll note the double occurrence of Strawson. In example.idx I read

\indexentry{Strawson, Peter}{1}
\indexentry{Strawson, Peter@Strawson, Peter}{1}
\indexentry{Strawson, Peter}{2}
\indexentry{Strawson, Peter@Strawson, Peter}{3}
\indexentry{Strawson, Peter}{4}
\indexentry{Strawson, Peter@Strawson, Peter}{5}
\indexentry{Strawson, Peter@Strawson, Peter}{5}

Answer 1

For reasons that I don't really understand, the indexing made by biblatex issues a command of the form

\index{Strawson, Peter@Strawson, Peter}

as you can see by examining the .idx file

\indexentry{Strawson, Peter}{1}
\indexentry{Strawson, Peter@Strawson, Peter}{1}
\indexentry{Strawson, Peter}{2}
\indexentry{Strawson, Peter@Strawson, Peter}{3}
\indexentry{Strawson, Peter}{4}
\indexentry{Strawson, Peter@Strawson, Peter}{5}
\indexentry{Strawson, Peter@Strawson, Peter}{5}

You can work around this behavior by defining

\newcommand{\nindex}[1]{\index{#1@#1}}

and using \nindex{Strawson, Peter} in the text. After the change, here's the .idx file I get:

\indexentry{Strawson, Peter@Strawson, Peter}{1}
\indexentry{Strawson, Peter@Strawson, Peter}{1}
\indexentry{Strawson, Peter@Strawson, Peter}{2}
\indexentry{Strawson, Peter@Strawson, Peter}{3}
\indexentry{Strawson, Peter@Strawson, Peter}{4}
\indexentry{Strawson, Peter@Strawson, Peter}{5}
\indexentry{Strawson, Peter@Strawson, Peter}{5}

and here's the index, with a single entry:

Maybe there is a workaround also on the biblatex side, but I don't know it.

Answer 2

The result you are seeing has been correctly diagnosed by egreg. But there may be a simpler workaround. It's actually not down to \indexname, as I wrongly speculated, but to the treatment of prefixes "van" "von" "de la" etc.

If biblatex is "using prefixes" (which means it will always print Ludwig van Beethoven as Van Beethoven, Ludwig, with a capital) then it puts both a "printing" and a "sorting" entry into the index, separated by @. It does this so that it can have makeindex sort using "van Beethoven, Ludwig", but print "Van Beethoven, Ludwig". The latter requires the addition of a LaTeX command (\MakeCapital {van}) in the file, which would cause sorting difficulties if it was nakedly included in the index entry.

Simple Solution You can avoid this by setting the option useprefixes=false when loading biblatex. That may solve your problem, unless you need "useprefixes" i.e. you have entries like "van Beethoven" which you want print "Van Beethoven" and sorted under V. In most cases in English conventions of sorting at least this will be a good solution, and probably what you want.

Not so simple solution Alternatively, if you want to keep the "useprefixes" option, the following code tries to make sure that the additional naming (van Beethoven, Ludwig@\MakeCapital{van} Beethoven Ludwig) only gets used when the name actually has a prefix, and therefore solves the problem in your case (but you would then need to use egreg's approach if dealing with a name that did have a prefix, i.e. you would have to ensure that your index entries for names with a prefix took the form given above).

\makeatletter
\renewcommand*{\mkbibindexname}[4]{%
\ifuseprefix
   {\ifblank{#3}% no PREFIX
       {\@firstofone #1% remove spurious braces                                    
       \ifblank{#4}{}{ #4}%                                        
       \ifblank{#2#3}{}{,}%
       \ifblank{#2}{}{ #2}}%
       {#3 % PREFIX                                                      
         \@firstofone #1%removespuriousbraces
         \ifblank{#4}{}{ #4}%
         \ifblank{#2}{}{, #2}%
         \actualoperator
         \ifblank{#3}{}{\MakeCapital{#3} %
         #1%       
         \ifblank{#4}{}{ #4}%
         \ifblank{#2}{}{, #2}}}}
    {\@firstofone #1% NOT "using prefix" remove spurious braces                                    
     \ifblank{#4}{}{ #4}%                                                      
     \ifblank{#2#3}{}{,}%                                                      
     \ifblank{#2}{}{ #2}%                                                      
     \ifblank{#3}{}{ #3}}}
\makeatother

Answer 3

I use another solution: defining fake citation commands which print nothing, but add the author of the “cited” reference to the index.

The problem, as already pointed out, is that biblatex is liable to transform author names in various ways before adding them to the index; the @ issue mentioned in the question is just one of them. For instance, I had an annoying problem with special characters, like accents: to index the name “Châtelet, Émilie du”, biblatex would actually call \indexentry on Ch\IeC {\^a}telet, \IeC {\'E}milie du, and a manual call to \index{Châtelet, Émilie du} would therefore create a duplicate entry. So whenever I wanted to add an entry to the index manually, I had to check in the .idx file to see what biblatex had done, and then copy it, as barbara beeton and Paul Stanley suggested. It worked, but on top of being fairly illegible, I felt it wasn't very robust for my (big) document, as any change in biblatex internals or in my options (regarding prefixes, say) might break all of my manual entries.

Now, if I define:

\newbibmacro*{idxauthor}{%
  \ifciteindex
    {\indexnames{author}}
    {}}
\DeclareCiteCommand{\idxauthor}
  {}%
  {\usebibmacro{idxauthor}}
  {}
  {}

\newbibmacro*{idxeditor}{%
  \ifciteindex
    {\indexnames{editor}}
    {}}
\DeclareCiteCommand{\idxeditor}
  {}%
  {\usebibmacro{idxeditor}}
  {}
  {}

\newbibmacro*{idxtransl}{%
  \ifciteindex
    {\indexnames{translator}}
    {}}
\DeclareCiteCommand{\idxtransl}
  {}%
  {\usebibmacro{idxtransl}}
  {}
  {}

then I can call \idxauthor{strawson:1966} to add a manual index entry for Strawson, which relies on biblatex internals to issue exactly the same indexing command as a \cite{strawson:1966} but does nothing else (and in particular does not print Strawson (1966) or whatever).