Proper use of in:, \intitlepunct for @inbook entries in biblatex

Question

The following code produces what are (to me) unexpected results and I would like to know where I am going wrong. Here's the code:

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@bookinbook{robber-early-years,
  crossref  =   {robber-robberies},
  title     =   {Robbing Trains: The Early Years},
  pages     =   {33-245}}
@inbook{robber-greatest,
  crossref  =   {robber-robberies},
  title     =   {My Greatest Robbery Yet},
  pages     =   {456--468}}
@book{robber-robberies,
  author    =   {Robber, Great Train},
  title     =   {A Robber's Life},
  year      =   2014,
  publisher =   {Fictitious Emporium Ltd.},
  address   =   {Somewhere}}
\end{filecontents}
\usepackage{biblatex}
\makeatletter
  \renewcommand*{\intitlepunct}{\addspace}
  % http://tex.stackexchange.com/a/10686/39222
  \renewbibmacro{in:}{%
    \ifentrytype{article}{}{\printtext{\bibstring{in}\intitlepunct}}}
\makeatother
\bibliography{\jobname.bib}

\begin{document}

\autocites{robber-early-years}{robber-greatest}

\printbibliography

\end{document}

What I expect this to do for entry types which use the bibmacro in: and which are not of type @article is to use in or In followed by a breakable space rather than in or In followed by a colon etc. However, I get a full stop as well and I do not understand why:

I can avoid this by redefining the @inbook entry type:

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@bookinbook{robber-early-years,
  crossref  =   {robber-robberies},
  title     =   {Robbing Trains: The Early Years},
  pages     =   {33-245}}
@inbook{robber-greatest,
  crossref  =   {robber-robberies},
  title     =   {My Greatest Robbery Yet},
  pages     =   {456--468}}
@book{robber-robberies,
  author    =   {Robber, Great Train},
  title     =   {A Robber's Life},
  year      =   2014,
  publisher =   {Fictitious Emporium Ltd.},
  address   =   {Somewhere}}
\end{filecontents}
\usepackage{biblatex}
\makeatletter
  \renewcommand*{\intitlepunct}{\addspace}
  % http://tex.stackexchange.com/a/10686/39222
  \renewbibmacro{in:}{%
    \ifentrytype{article}{}{\printtext{\bibstring{in}\intitlepunct}}}
\makeatother
\bibliography{\jobname.bib}
\makeatletter
\DeclareBibliographyDriver{inbook}{%
  \usebibmacro{bibindex}%
  \usebibmacro{begentry}%
  \usebibmacro{author/translator+others}%
  \setunit{\labelnamepunct}\newblock
  \usebibmacro{title}%
  \newunit
  \printlist{language}%
  \newunit\newblock
  \usebibmacro{byauthor}%
  \newunit\newblock
  \usebibmacro{in:}%
%   \usebibmacro{bybookauthor}%
%   \newunit\newblock
  \usebibmacro{maintitle+booktitle}%
  \newunit\newblock
  \usebibmacro{byeditor+others}%
  \newunit\newblock
  \printfield{edition}%
  \newunit
  \iffieldundef{maintitle}
    {\printfield{volume}%
     \printfield{part}}
    {}%
  \newunit
  \printfield{volumes}%
  \newunit\newblock
  \usebibmacro{series+number}%
  \newunit\newblock
  \printfield{note}%
  \newunit\newblock
  \usebibmacro{publisher+location+date}%
  \newunit\newblock
  \usebibmacro{chapter+pages}%
  \newunit\newblock
  \iftoggle{bbx:isbn}
    {\printfield{isbn}}
    {}%
  \newunit\newblock
  \usebibmacro{doi+eprint+url}%
  \newunit\newblock
  \usebibmacro{addendum+pubstate}%
  \setunit{\bibpagerefpunct}\newblock
  \usebibmacro{pageref}%
  \newunit\newblock
  \iftoggle{bbx:related}
    {\usebibmacro{related:init}%
     \usebibmacro{related}}
    {}%
  \usebibmacro{finentry}}
\makeatother

\begin{document}

\autocites{robber-early-years}{robber-greatest}

\printbibliography

\end{document}

But this is surely not the best way to do this. It strikes me as odd that the driver for @inbook tries to use the book author as well as the author. As I understand it, @inbook and @bookinbook are for precisely those cases in which the author of the whole is also the author of a distinct part. An example for @bookinbook mentioned in the manual is the collected works of an author. But in that case, you would not expect a distinct author and it seems silly to include the author twice when laying out the entry.

This makes me think that I'm fundamentally misunderstanding something here - either about how the commands work or about the intended purpose of these entry types.

If I stick to the standard definition of in:, I don't get spurious full stops but I do, of course, get the colon I wanted to get rid of. (This looks especially silly for non-article entries, in my view, and in is altogether unnecessary for article entries so eliminating the colon seemed a good option. The comment in the code is to the question I took the code from but I cannot get it to work 'right'.)

Can anybody explain how to do this correctly and how these are intended to be used?

Answer 1

Although I can't promise I've understood it, I think that by using \addspace you are confusing the punctuation tracker. Because the tracker sees that no relevant punctuation mark has been printed, when the next \newunit occurs (immediately after bybookauthor has printed nothing), it backs up, removes your space, and inserts \newunitpunct.

You can sort this out by defining \intitlepunct as \addspace\nopunct, which I think should be safe in this context.

Answer 2

biblatex has a punctuation tracker and a punctuation buffer, a \newunit or \setunit command inserts the respective punctuation mark into the buffer, it does not print the punctuation mark straight away, subsequent \setunits overwrite the buffer.

So the \addspace in the buffer is overwritten by the \newunit following the bybookauthor macro. Luckily for us, the biblatex developers got into trouble with this concept at some point and decided to add \printunit. \printunit inserts a punctuation mark that persist in the buffer, i.e. cannot be overwritten by other \setunits.

If we add the \printunit command to the redefinition of in:

\renewbibmacro{in:}{%
  \ifentrytype{article}{}{\printtext{\bibstring{in}\printunit{\intitlepunct}}}}

the output should be as expected. (I don't know why this is not the default, after all, the "in:" is always printed and one would want it to be followed by the proper punctuation mark as defined in \intitlepunct.)

This problem seems to occur only with \intitlepunct set to \addspace or \space, any of the other \add commands work like a charm without \printunit.

You can read more about the wonderful world of punctuation with biblatex in §4.7 Punctuation and Spacing, p. 189 of the biblatex documentation.

\documentclass{article}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@bookinbook{robber-early-years,
  crossref  =   {robber-robberies},
  title     =   {Robbing Trains: The Early Years},
  pages     =   {33-245}}
@inbook{robber-greatest,
  crossref  =   {robber-robberies},
  title     =   {My Greatest Robbery Yet},
  pages     =   {456--468}}
@book{robber-robberies,
  author    =   {Robber, Great Train},
  title     =   {A Robber's Life},
  year      =   2014,
  publisher =   {Fictitious Emporium Ltd.},
  address   =   {Somewhere}}
\end{filecontents*}
\usepackage{biblatex}

\renewcommand*{\intitlepunct}{\addspace}
\renewbibmacro{in:}{%
  \ifentrytype{article}{}{\printtext{\bibstring{in}\printunit{\intitlepunct}}}}

\addbibresource{\jobname.bib}

\begin{document}
  \autocites{robber-early-years}{robber-greatest}
  \printbibliography
\end{document}