Biblatex: Convert doi-url into doi field

Question

I use biblatex and would like my bibliography to only include a DOI field, whenever there is DOI information available. This involves two things:

1. Biblatex has to suppress the URL field whenever a DOI field is present. This can be done with the following code in the preamble. (This is a simplified version of Joseph Wright's answer here).

   \renewbibmacro*{doi+eprint+url}{%
     \iftoggle{bbx:doi}
       {\printfield{doi}}
       {}%
   \newunit\newblock
     \iftoggle{bbx:eprint}
       {\usebibmacro{eprint}}
       {}%
   \newunit\newblock
     \iftoggle{bbx:url}
           {%
         \iffieldundef{doi}
   {\usebibmacro{url+urldate}}
           {%
             \clearfield{url}%  
           }%
       }
       {}} 
   

   So everytime a DOI field is present in the bibtex file, the URL field is cleared.

2. My bibtex file is exported from Zotero. Unfortunately Zotero does not provide DOI fields for all entry types (yet), so I often enter the DOI information into the URL field like http://dx.doi.org/10.1145/1364782.1364794. So my question is: Is it possible to have biblatex take the DOI information from the URL field, store it into the DOI field and write only that into the bibliography?

   I guess one would have to modify the \usebibmacro{url+urldate} conditional: First, check whether the URL field contains "dx.doi.org/" (ideally one should allow for http and https). If it does, take everything after "dx.doi.org/", copy it into the DOI field (with \restorefield?) and \printfield{doi}. If it does not, i.e. if it is not a DOI-URL, \usebibmacro{url+urldate}.

Is that possible?

Answer 1

If biber is used as backend, then one can use the \DeclareSourcemap facilities to change fields.

For the case at hand a solution is to remap url entries with dx.doi.org as initial part using the following code:

\DeclareSourcemap{
  \maps[datatype=bibtex]{
    \map{
      \step[ % copies url to doi field if it starts with http://dx.doi.org/
        fieldsource=url,
        match=\regexp{http://dx.doi.org/(.+)},
        fieldtarget=doi,
      ]
    \step[ % removes http://dx.doi.org/ string from doi field
      fieldsource=doi,
      match=\regexp{http://dx.doi.org/(.+)},
      replace=\regexp{$1}
    ]
    }
  \map{ % removes url + urldate field from all entries that have a doi field
   \step[fieldsource=doi, final]
   \step[fieldset=url, null]
   \step[fieldset=urldate, null]
   }
 }
}

The actual value inside \regexp can be adjusted.

In the first step we create a doi field for each entry where the url field matches the regexp, and the novel field has the value of the url field. In the second step we remove the doi "namespace".

In the second \map sequence the url and urldate fields are cleared if a doi field is present, to mimic the behavior in the first part of the original question.