Envolviendo bibmacro existente

Question

Estoy buscando una manera de biblateximprimir solo las URL si no se especifica ningún DOI (en mi caso, los DOI conducen a enlaces en las referencias de todos modos, lo que hace que la URL sea algo redundante).

Se me ocurrió esto (pero parece causar un bucle sin fin ya que la compilación no termina...):

\renewbibmacro*{url+urldate}{%
  \iffieldundef{doi}
    {\usebibmacro{url+urldate}}
    {}%
}

Parece que guardar la macro \letno funciona debido a +...

¿Alguna idea de cómo hacer esto correctamente?

M(N)WEB:

\documentclass{article}
\usepackage[style=authoryear-comp]{biblatex}
\usepackage{hyperref}

%\renewbibmacro*{url+urldate}{%
%  \iffieldundef{doi}
%    {\usebibmacro{url+urldate}}
%    {}%
%

\addbibresource{\jobname.bib}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{key,
  author = {Author, A.},
  year = {2001},
  title = {Title},
  publisher = {Publisher},
  archivePrefix = {arXiv},
  arxivId = {1607.07249},
  doi = {10.1007/978-3-319-49004-5_22},
  eprint = {1607.07249},
  url = {http://link.springer.com/10.1007/978-3-319-49004-5_22},
}
\end{filecontents}

\begin{document}
\nocite{*}
\printbibliography
\end{document}

Answer 1

No existe \letbibmacro(y es posible que presente una solicitud de función), pero no es difícil crear una:

\documentclass{article}
\usepackage[style=authoryear-comp]{biblatex}
\usepackage{hyperref}

\newcommand{\letbibmacro}[2]{%
  \csletcs{abx@macro@#1}{abx@macro@#2}%
}

\letbibmacro{orig-url+urldate}{url+urldate}
\renewbibmacro*{url+urldate}{%
  \iffieldundef{doi}
    {\usebibmacro{orig-url+urldate}}
    {}%
}

\addbibresource{\jobname.bib}
\usepackage{filecontents}
\begin{filecontents}{\jobname.bib}
@book{key,
  author = {Author, A.},
  year = {2001},
  title = {Title},
  publisher = {Publisher},
  archivePrefix = {arXiv},
  arxivId = {1607.07249},
  doi = {10.1007/978-3-319-49004-5_22},
  eprint = {1607.07249},
  url = {http://link.springer.com/10.1007/978-3-319-49004-5{\_}22},
}
@book{key2,
  author = {Author, A.},
  year = {2001},
  title = {Title},
  publisher = {Publisher},
  archivePrefix = {arXiv},
  arxivId = {1607.07249},
  eprint = {1607.07249},
  url = {http://link.springer.com/10.1007/978-3-319-49004-5{\_}22},
}
\end{filecontents}

\begin{document}
\nocite{*}
\printbibliography
\end{document}

Answer 2

Ya obtuviste excelentes respuestas a la pregunta que hiciste, así que pensé en agregar dos soluciones para el problema que deseas resolver.

Puedes usar

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[fieldsource=doi, final]
      \step[fieldset=url, null]
      \step[fieldset=urldate, null]
    }
  }
}

o

\AtEveryBibitem{%
  \iffieldundef{doi}
    {}
    {\clearfield{url}\clearfield{urlyear}}%
}

no imprimir la URL si hay un DOI presente.

Answer 3

Para imprimir condicionalmente la URL, puede envolverla en\iffieldundef{doi}{}{}

\documentclass{article}
\usepackage[style=authoryear-comp]{biblatex}
\usepackage{hyperref}

% print url if no doi
\renewbibmacro*{doi+eprint+url}{%
  \printfield{doi}
  \newunit\newblock
  \iftoggle{bbx:eprint}{
      \usebibmacro{eprint}
  }{}%
  \newunit\newblock
  \iffieldundef{doi}{
      \usebibmacro{url+urldate}}
      {}
}
\addbibresource{\jobname.bib}
\usepackage{filecontents}
\begin{filecontents*}{\jobname.bib}
@book{key,
  author = {Author, A.},
  year = {2001},
  title = {Title},
  publisher = {Publisher},
  archivePrefix = {arXiv},
  arxivId = {1607.07249},
  doi = {10.1007/978-3-319-49004-5_22},
  eprint = {1607.07249},
  url = {http://link.springer.com/10.1007/978-3-319-49004-5{\_}22},
}

@book{keyx,
  author = {Author, A.},
  year = {2001},
  title = {Title},
  publisher = {Publisher},
  archivePrefix = {arXiv},
  arxivId = {1607.07249},
  url = {http://link.springer.com/10.1007/978-3-319-49004-5{\_}22},
}
\end{filecontents*}

\begin{document}
\nocite{*}
\printbibliography
\end{document}