biblatex-chicago: translationas does not work without translator name

Edited: title changed to use translationas instead of translatedas, since the former is the correct name for the relation. I have left the latter in the question.

In my bibliography, I want to inform readers of the English translation of a work I cite. If I just use the translatedas relation to link the two entries, nothing is printed between them:

This seems likely to confuse readers, as well as not corresponding to the Manual (16th ed., 14.109). So I want to add "translated as" before the data for the translation. I can do that by defining the bibliography string translatedas, which works fine with verbose-ibid, but with biblatex-chicago it produces two spurious commas and drops some punctuation and spacing between elements:

The problem depends on the lack of a translator name. Furet's book actually does have a translator, and if her name is included in the entry then all goes well. However, in my case, the translation I want to cite is anonymous. How can I add a relation to an anonymous translation?

MWE:

\documentclass{article}
\usepackage[american]{babel}
\usepackage[babel]{csquotes}
\usepackage[backend=biber]{biblatex-chicago}
\NewBibliographyString{translatedas}
\DefineBibliographyStrings{english}{translatedas = {translated as}}
\nocite{furet:related}
\begin{filecontents}{\jobname.bib}
@book{furet:passing:eng,
Author = {Furet, François},
Location = {Chicago},
Publisher = {University of Chicago Press},
Title = {The Passing of an Illusion},
Year = {1999}
}

@book{furet:related,
Author = {Furet, François},
Location = {Paris},
Publisher = {Éditions Robert Laffont},
Related = {furet:passing:eng},
Relatedtype = {translatedas},
Title = {Le passé d'une illusion},
Year = {1995}
}

\end{filecontents}
\begin{document}
\printbibliography
\end{document}


The example below uses the pre-defined relatedtype/bibstring translationas, but the same could be done for a new translatedas.

Apparently, the default related driver of biblatex-chicago does not give good results in your case (I did not investigate in depth why the punctuation is missing), but we can adapt related:bytranslator a bit and just throw out the explicit printing of the translator.

\documentclass{article}
\usepackage[american]{babel}
\usepackage[babel]{csquotes}
\usepackage[backend=biber]{biblatex-chicago}

\makeatletter
\newbibmacro*{related:translationas}[1]{%
\entrydata{#1}{%
\usebibmacro{at+every+item}%
\renewbibmacro*{name:hook}[1]{%
\ifnumequal{\value{listcount}}{1}%
{\begingroup
\mkrelatedstring%
\lbx@initnamehook{#1}%
\endgroup}%
{}}%
\usebibmacro{cite:origfull}}}%
\makeatother

\nocite{furet:related}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{furet:passing:eng,
Author    = {Furet, François},
Location  = {Chicago},
Publisher = {University of Chicago Press},
Title     = {The Passing of an Illusion},
Year      = {1999},
}
@book{furet:related,
Author      = {Furet, François},
Location    = {Paris},
Publisher   = {Éditions Robert Laffont},
Related     = {furet:passing:eng},
Relatedtype = {translationas},
Title       = {Le passé d'une illusion},
Year        = {1995},
}
\end{filecontents}

That said, if there is a translator in the related work it usually gives much nicer results to use the relatedtype bytranslator instead of translationas.