Bibliography with custom data model not printing

Question

I previously asked a question here and received a very useful reply which solved (most of) my dilemma. I have realised, however, that the bibliography is not printing when I use crossref in a 'master' entry in my .bib file. These 'master' or 'dummy' entries are used for those sources which would otherwise make duplicate bibliography entries simply due to their broad nature.

Below is my minimum working example showing two source citation entries - one which prints and one which does not - and the master source citation.

MWE:

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

\usepackage{filecontents}
\begin{filecontents}{freeform.dbx}
\DeclareDatamodelEntrytypes{freeform}
\DeclareDatamodelFields[type=field,datatype=literal]{
  bibliography,
  cite,
  firstcite,
}
\DeclareDatamodelEntryfields[freeform]{
  bibliography,
  cite,
  firstcite,
  sortkey,
}
\end{filecontents}

\usepackage[style=verbose, backend=biber, datamodel=freeform]{biblatex}

\DeclareBibliographyDriver{freeform}{%
  \usebibmacro{bibindex}%
  \usebibmacro{begentry}%
  \printfield{bibliography}%
  \setunit{\bibpagerefpunct}\newblock
  \usebibmacro{pageref}%
  \newunit\newblock
  \iftoggle{bbx:related}
    {\usebibmacro{related:init}%
     \usebibmacro{related}}
    {}%
  \usebibmacro{finentry}}


\renewbibmacro*{cite:full}{%
  \ifentrytype{freeform}
    {\iffieldundef{firstcite}
       {\usebibmacro{cite:short}}
       {\printfield{firstcite}}}
    {\usebibmacro{cite:full:citepages}%
     \printtext[bibhypertarget]{%
       \usedriver
         {\DeclareNameAlias{sortname}{default}}
         {\thefield{entrytype}}}%
     \usebibmacro{shorthandintro}}}

\renewbibmacro*{cite:short}{%
  \ifentrytype{freeform}
    {\printfield{cite}}
    {\printnames{labelname}%
     \setunit*{\printdelim{nametitledelim}}%
     \printtext[bibhyperlink]{%
       \printfield[citetitle]{labeltitle}}}}

\DeclareSourcemap{
  \maps[datatype=bibtex,overwrite=false]{
    \map{
      \pertype{freeform}
      \step[fieldsource=bibliography]
      \step[fieldset=sortkey, origfieldval]
    }
  }
}

\begin{filecontents}{sample.bib}
@freeform{baptism,
  cite         = {Church of England (Spondon, Derbs.), Parish Registers, vol.\ 9, p.\ 1, Thompson (9 June 1824).},
  firstcite    = {Church of England (Spondon, Derbyshire, England), Parish Registers, vol.\ 9, p.\ 1, baptism of Emma Thompson (9 June 1824); digital images, Ancestry.com (\url{http://ancestry.com.au}: accessed 4 July 2018), citing Derbyshire Record Office, Matlock.},
  bibliography = {Church of England (Spondon, Derbyshire, England). Parish Registers. Digital images. \textit{Ancestry.com}. \url{http://ancestry.com.au}: 2018},
  keywords     = {church}
}
@freeform{marriage,
  cite         = {Church of England (Derby, Derbs.), Parish Registers, vol.\ 4, p.\ 3, Smith-Bloggs (20 January 1815).},
  firstcite    = {Church of England (Derby, Derbyshire, England), Parish Registers, vol.\ 4, p.\ 3, marriage of John Smith and Jane Bloggs (20 January 1815); digital images, Ancestry.com (\url{http://ancestry.com.au}: accessed 1 July 2018), citing Derbyshire Record Office, Matlock.},
  options      = {skipbib},
  crossref     = {coe:derb}
}
@freeform{coe:derb,
  bibliography = {Church of England (Derby, Derbyshire, England). Parish Registers. Digital images. Ancestry.com. \url{http://ancestry.com.au}: 2018},
  keywords     = {church}
}
\end{filecontents}

\addbibresource{sample.bib}


\begin{document}
Lorem\footcite{marriage} ipsum\footcite{baptism}
\printbibliography[keyword=church, title={Church Records}]
\end{document}

Output:

How do I get the 'master' source to print in my bibliography?

(I'm still a newbie, so please excuse any glaring errors or oversights!)

Answer 1

If you use crossref = {coe:derb} to refer to coe:derb from an entry, then coe:derb will only be added to the bibliography if it was crossref'd more often at least mincrossrefs times, where mincrossrefs is a biblatex option, whose value you can choose freely. The default value is mincrossrefs=2, that's why we got to see coe:derb in How to set up BibLaTeX for use with 'freeform' citations but not here.

The solution is simple: Load biblatex with the option mincrossrefs=1.

MWE

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

\usepackage{filecontents}
\begin{filecontents}{freeform.dbx}
\DeclareDatamodelEntrytypes{freeform}
\DeclareDatamodelFields[type=field,datatype=literal]{
  bibliography,
  cite,
  firstcite,
}
\DeclareDatamodelEntryfields[freeform]{
  bibliography,
  cite,
  firstcite,
  sortkey,
}
\end{filecontents}

\usepackage[style=verbose, backend=biber, datamodel=freeform, mincrossrefs=1]{biblatex}

\DeclareBibliographyDriver{freeform}{%
  \usebibmacro{bibindex}%
  \usebibmacro{begentry}%
  \printfield{bibliography}%
  \setunit{\bibpagerefpunct}\newblock
  \usebibmacro{pageref}%
  \newunit\newblock
  \iftoggle{bbx:related}
    {\usebibmacro{related:init}%
     \usebibmacro{related}}
    {}%
  \usebibmacro{finentry}}


\renewbibmacro*{cite:full}{%
  \ifentrytype{freeform}
    {\iffieldundef{firstcite}
       {\usebibmacro{cite:short}}
       {\printfield{firstcite}}}
    {\usebibmacro{cite:full:citepages}%
     \printtext[bibhypertarget]{%
       \usedriver
         {\DeclareNameAlias{sortname}{default}}
         {\thefield{entrytype}}}%
     \usebibmacro{shorthandintro}}}

\renewbibmacro*{cite:short}{%
  \ifentrytype{freeform}
    {\printfield{cite}}
    {\printnames{labelname}%
     \setunit*{\printdelim{nametitledelim}}%
     \printtext[bibhyperlink]{%
       \printfield[citetitle]{labeltitle}}}}

\DeclareSourcemap{
  \maps[datatype=bibtex,overwrite=false]{
    \map{
      \pertype{freeform}
      \step[fieldsource=bibliography]
      \step[fieldset=sortkey, origfieldval]
    }
  }
}

\begin{filecontents}{sample.bib}
@freeform{baptism,
  cite         = {Church of England (Spondon, Derbs.), Parish Registers, vol.\ 9, p.\ 1, Thompson (9 June 1824).},
  firstcite    = {Church of England (Spondon, Derbyshire, England), Parish Registers, vol.\ 9, p.\ 1, baptism of Emma Thompson (9 June 1824); digital images, Ancestry.com (\url{http://ancestry.com.au}: accessed 4 July 2018), citing Derbyshire Record Office, Matlock.},
  bibliography = {Church of England (Spondon, Derbyshire, England). Parish Registers. Digital images. \textit{Ancestry.com}. \url{http://ancestry.com.au}: 2018},
  keywords     = {church}
}
@freeform{marriage,
  cite         = {Church of England (Derby, Derbs.), Parish Registers, vol.\ 4, p.\ 3, Smith-Bloggs (20 January 1815).},
  firstcite    = {Church of England (Derby, Derbyshire, England), Parish Registers, vol.\ 4, p.\ 3, marriage of John Smith and Jane Bloggs (20 January 1815); digital images, Ancestry.com (\url{http://ancestry.com.au}: accessed 1 July 2018), citing Derbyshire Record Office, Matlock.},
  options      = {skipbib},
  crossref     = {coe:derb}
}
@freeform{coe:derb,
  bibliography = {Church of England (Derby, Derbyshire, England). Parish Registers. Digital images. Ancestry.com. \url{http://ancestry.com.au}: 2018},
  keywords     = {church}
}
\end{filecontents}

\addbibresource{sample.bib}


\begin{document}
Lorem\footcite{marriage} ipsum\footcite{baptism}
\printbibliography[keyword=church, title={Church Records}]
\end{document}