Bibliography with biblatex: how to achieve bold labels using the authoryear-style?

Question

I am currently writing my thesis with LaTeX using biblatex for citations and bibliography. I try to match a formal request regarding the first part of the bibliographic entries which have to look like "Meyer, B. (1990):" or when having more than two names "Meyer, B.; Wang, S. et al. (1992):". The rest of the entry already fits the requested. By tweaking the authoryear-style with Google-collected pieces I got some parts of it right, but not all of them. My biggest problem seems to be "et al." which is either always bold or never. Having it always bold causes problems with some editor listings. The same problem occurs with name-prefixes like "de la Fuentes" as the example shows.

So I would like to know if there is any possibility of addressing the label of the entries with a command like \mkbibbold in general instead of separately changing every part?

Here is an example of what I got so far (my excuses for its length but I did not find anything that can be shortened):

    \documentclass[ngerman, 12pt, a4paper, oneside, notitlepage]{scrreprt}
       \usepackage[utf8]{inputenc}
       \usepackage[ngerman]{babel}
       \usepackage[babel,german=quotes]{csquotes} 

    \usepackage [backend=bibtex,style=authoryear] {biblatex}
    \ExecuteBibliographyOptions{hyperref=true, firstinits=true, isbn=false, url=true, doi=false, sorting=nyt, minnames=1, maxcitenames=2, maxbibnames=2, language=ngerman, alldates=short, punctfont=true, autopunct=false, block=none, dashed=false}
       \addbibresource{literatur.bib} 
       \usepackage{filecontents} 

        \AtBeginBibliography{
            \renewcommand*{\multinamedelim}{\textbf\addsemicolon\space}
            \renewcommand*{\finalnamedelim}{\textbf\addsemicolon\space}
            \renewcommand*{\nameyeardelim}{\textbf\addcomma\space}
            \renewcommand*{\labelnamepunct}{\addcolon\space}
            \renewcommand*{\newunitpunct}{\addcomma\space}}

        \DefineBibliographyStrings{ngerman}{
            sequens = {f},  sequentes = {ff}} 
        \DefineBibliographyStrings{ngerman}{
            editors = {\mkbibbold{Hrsg.}},  editor = {\mkbibbold{Hrsg.}}, 
            andothers = {et\addspace al\adddotspace}, andmore = {et\addspace al\adddotspace}} % defining et al.

        \DeclareNameAlias{sortname}{last-first}

        \AtBeginBibliography{
            \renewcommand*{\mkbibnamelast}[1]{%bold names in label
            \ifmknamesc{\mkbibbold{#1}}{#1}}
            \renewcommand*{\mkbibnamefirst}[1]{
            \ifmknamesc{\mkbibbold{#1}}{#1}}
            \renewcommand*{\mkbibnameprefix}[1]{
            \ifboolexpr{ test {\ifmknamesc} and test {\ifuseprefix} }{\mkbibbold{#1}}{#1}}
            \def\ifmknamesc{%bold editors in labels, but not in content
            \ifboolexpr{ test {\ifcurrentname{labelname}}
            or test {\ifcurrentname{author}}
            or ( test {\ifnameundef{author}} and test {\ifcurrentname{editor}} ) }}

        \renewbibmacro*{name:andothers}{
            \ifthenelse{\value{listcount}=\value{liststop}\AND 
            \ifmorenames}
            {\ifnum\value{liststop}>1 \finalandcomma\fi 
            \andothersdelim\textbf{\bibstring{andothers}}}
            {}}
            }

        \setlength {\bibitemsep}{18pt}
        \setlength {\bibhang}{0.2cm}
        \DeclareFieldFormat[article, book, inbook, incollection, inproceedings, patent, thesis, unpublished, misc] 
            {title}{\mkbibquote{#1\isdot}}
        \DeclareFieldFormat [article, book, inbook, incollection, inproceedings, patent, thesis, unpublished, misc] 
            {date}{\mkbibbold{#1}}%bold-printed year in labels
        \DeclareFieldFormat{parens}{\mkbibbold{\mkbibparens{#1}}}%round brackets for year in label

    \usepackage[colorlinks, allcolors=black]{hyperref}
    \usepackage{url} 
    \urlstyle{same}

\begin{filecontents*}{literatur.bib} 
@article{nature, 
   author      =   {Rosa Rademakers and Manuela Neumann and Ian R. Mackenzie}, 
   title      =   {Advances in understanding the molecular basis of frontotemporal dementia - elongated title}, 
   journal      =   {Nature Reviews Neurology}, 
   volume      =   {8}, 
   year      =   {2012}, 
   pages      =   {423-434}, 
   doi         =   {10.1038/nrneurol.2012.117}} 
@article{fuente, 
   author      =   {D. de la Fuente and J.G. Castaño and M. Morcillo}, 
   title      =   {Long-term atmospheric corrosion of zinc}, 
   journal      =   {Corrosion Science}, 
   volume      =   {49}, 
   year      =   {2007}, 
   pages      =   {1420–1436 www.elsevier.com/locate/corsci}}, 
 @incollection{Rocca2007a,
   author = {Rocca, Emmanuel and Mirambet, Fran\c{c}ois},
   booktitle = {Corrosion of Metallic Heritage Artefacts: Investigation, Conservation and Prediction of Long Term Behaviour},
   chapter = {18},
   editor = {Philippe Dillmann and Pedro Piccardo and Gerard Beranger},
   pages = {308-334},
   title = {{Corrosion inhibitors for metallic artefacts: temporary protection}},
   year = {2007}}

\end{filecontents*} 

\begin{document} 
   Test\cite{nature}\\
   another test \cite{fuente} and \cite{Rocca2007a}
   \printbibliography
\end{document} 

Answer 1

Your example wasn't quite minimal, so I removed some redefinitions not related to the actual problem (achieving bold labels). I suggest to simply wrap the author bibmacro (which also prints the year in authoryear styles) into a \mkbibbold -- I use the xpatch package to do so. (In addition, one has to make the colon after the year bold by redefining \labelnamepunct.)

EDIT: For works without author, the bbx:editor bibmacro must be changed accordingly.

\documentclass{scrreprt}

\usepackage[utf8]{inputenc}
\usepackage[ngerman]{babel}
\usepackage[babel,german=quotes]{csquotes} 

\usepackage[style=authoryear]{biblatex}
\ExecuteBibliographyOptions{firstinits=true,maxnames=2}

\setlength{\bibitemsep}{18pt}
\setlength{\bibhang}{0.2cm}

\DeclareNameAlias{sortname}{last-first}

\AtBeginBibliography{%
  \renewcommand*{\multinamedelim}{\addsemicolon\space}%
  \renewcommand*{\finalnamedelim}{\addsemicolon\space}%
}

\DefineBibliographyStrings{ngerman}{%
  andothers = {et\addspace al\adddotspace},%
  andmore = {et\addspace al\adddotspace},%
}

\usepackage{xpatch}
\xpretobibmacro{author}{\mkbibbold\bgroup}{}{}
\xapptobibmacro{author}{\egroup}{}{}
\xpretobibmacro{bbx:editor}{\mkbibbold\bgroup}{}{}
\xapptobibmacro{bbx:editor}{\egroup}{}{}

\renewcommand*{\labelnamepunct}{\mkbibbold{\addcolon\space}}

\usepackage{filecontents} 

\begin{filecontents*}{\jobname.bib} 
@article{nature, 
   author      =   {Rosa Rademakers and Manuela Neumann and Ian R. Mackenzie}, 
   title      =   {Advances in understanding the molecular basis of frontotemporal dementia - elongated title}, 
   journal      =   {Nature Reviews Neurology}, 
   volume      =   {8}, 
   year      =   {2012}, 
   pages      =   {423-434}, 
   doi         =   {10.1038/nrneurol.2012.117},
} 
@article{fuente, 
   author      =   {D. de la Fuente and J.G. Castaño and M. Morcillo}, 
   title      =   {Long-term atmospheric corrosion of zinc}, 
   journal      =   {Corrosion Science}, 
   volume      =   {49}, 
   year      =   {2007}, 
   pages      =   {1420–1436},
}
 @incollection{Rocca2007a,
   author = {Rocca, Emmanuel and Mirambet, Fran\c{c}ois},
   booktitle = {Corrosion of Metallic Heritage Artefacts: Investigation, Conservation and Prediction of Long Term Behaviour},
   chapter = {18},
   editor = {Philippe Dillmann and Pedro Piccardo and Gerard Beranger},
   pages = {308-334},
   title = {Corrosion inhibitors for metallic artefacts: temporary protection},
   year = {2007},
}
@misc{A01,
  editor = {Author, A.},
  year = {2001},
  title = {Alpha},
}
\end{filecontents*} 

\addbibresource{\jobname.bib} 

\nocite{*}

\begin{document}

\printbibliography

\end{document}

Answer 2

You can wrap the instruction to print the string "et al" in a conditional, and to switch it on and off. Given the order in which the various bibliographic information is presented we can set the switch on at the begin of each reference, and we can switch off after the container title.

\newtoggle{boldetal}
\renewbibmacro{begentry}{\settoggle{boldetal}{true}}
\def\mymkbibbold{\iftoggle{boldetal}{\mkbibbold}{}} 

The first line create a toggle. Then we use the hook begentry to set the toggle true at the begin of each reference. Then the third line is a shortcut: if the toggle is true we print using boldface otherwise we do nothing.

Based on this, the definition of biblatex macro name:andother is modified to use the new shortcut.

\renewbibmacro*{name:andothers}{% 
   \ifthenelse{\value{listcount}=\value{liststop}\AND 
    \ifmorenames}%
    {\ifnum\value{liststop}>1 \finalandcomma\fi 
    \andothersdelim\mymkbibbold{\bibstring{andothers}}}
    {}}

Finally, the switch to turn the toggle off is inserted with the title.

\DeclareFieldFormat[article, book, inbook, incollection, inproceedings, patent, thesis, unpublished, misc] 
    {title}{\mkbibquote{#1\isdot}\global\settoggle{boldetal}{false}}

By the way in your code, there are spaces before comments, i.e., { % if you remove them, with the changes above you get:

Answer 3

Because I had a similar problem, but just needed the colon after the date-section to be bold.

I just changed the

FUNCTION {date.block}
{
  ":" *
  add.blank
}

in my .bst file to

FUNCTION {date.block}
{
  "\textbf{:}" *
  add.blank
}