biblatex: change which fields are printed for different entry types in the preamble

Question

I wish to print the url field using the authoryear style but only for @MISC entry types.

My hacky solution is to set style=authoryear, url=false in the package options, and set the title field equal to url for @MISC entries. This is OK for me in this particular case, because the title of the @MISC entries are not important, but I would like to know whether there is a better way to do this.

The url -> title is achieved through the following preamble code

\DeclareSourcemap{
    \maps[datatype=bibtex]{
        \map[overwrite]{
            \pertype{misc}
            \step[fieldsource=url]
            \step[fieldset=title, origfieldval]
        }
    }
}

Answer 1

0. Use @online instead of @misc

The @online entry type always shows the url field regardless of the global url option setting.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[backend=biber, style=authoryear, url=false]{biblatex}


\begin{filecontents}{\jobname.bib}
@online{bronto,
  author  = {Anne Elk},
  title   = {Towards a Unified Theory on Brontosauruses},
  date    = {1972-11-16},
  url     = {http://example.edu/~elk/bronto.pdf},
  urldate = {2015-09-07},
}
\end{filecontents}
\addbibresource{\jobname.bib}


\begin{document}
\autocite{bronto}
\printbibliography
\end{document}

1. Set the url option per type (biblatex 3.15 and above)

Since biblatex 3.15 you can set the url option per type in the standard styles (https://github.com/plk/biblatex/pull/1000), so you can disable url globally, but reenable it for @misc.

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[backend=biber, style=authoryear, url=false]{biblatex}
\ExecuteBibliographyOptions[misc]{url=true}

\begin{filecontents}{\jobname.bib}
@misc{bronto,
  author  = {Anne Elk},
  title   = {Towards a Unified Theory on Brontosauruses},
  date    = {1972-11-16},
  url     = {http://example.edu/~elk/bronto.pdf},
  urldate = {2015-09-07},
}
\end{filecontents}
\addbibresource{\jobname.bib}


\begin{document}
\autocite{bronto}
\printbibliography
\end{document}

2. Delete the url field with a sourcemap

This solution does not use the url option. Instead it deletes the url and urldate fields for all types except @misc with a sourcemap.

The advantage is that the field is really gone for good and is not used to generate label data (for example the label date).

\documentclass[british]{article}
\usepackage[T1]{fontenc}
\usepackage[utf8]{inputenc}
\usepackage{babel}
\usepackage{csquotes}

\usepackage[backend=biber, style=authoryear]{biblatex}

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \pernottype{misc}
      \step[fieldset=url, null]
      \step[fieldset=urldate, null]
    }
  }
}

\begin{filecontents}{\jobname.bib}
@misc{bronto,
  author  = {Anne Elk},
  title   = {Towards a Unified Theory on Brontosauruses},
  date    = {1972-11-16},
  url     = {http://example.edu/~elk/bronto.pdf},
  urldate = {2015-09-07},
}
\end{filecontents}
\addbibresource{\jobname.bib}


\begin{document}
\autocite{bronto}
\printbibliography
\end{document}

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In all cases the output will be