Underline and make bold some authors in a bib file

Question

For some (stupid) report, I have to put a bibliography with some authors in bold and some authors underlined.

Thanks to some posts/answer here, I succeed to make a specific one bold. However, all other tricks tested here to make other underlined failed (either not compiling or not producing anything).

Here is a MWE for the bold. Let say I would like Billy Bob and Jane Doe underlined.

\documentclass[a4paper,11pt]{article}
\usepackage[T1]{fontenc} 
\usepackage{hyperref}
\usepackage{ulem}
\usepackage[style=alphabetic, maxnames=99, sorting=ydnt, backend=bibtex]{biblatex}
\begin{filecontents}{\jobname.bib}
@article{article1,
  author={Smith, John and Doe, Jane and Foo, Bar},
  title={Title},
  journal={Journal}
}
@article{article2,
  author={Smith, John and Billy, Bob},
  title={Title2},
  journal={Journal2}
}
\end{filecontents}
\addbibresource{\jobname.bib}
\DeclareBibliographyDriver{article}{%
  \printfield{title} %
  \par
  \newblock%
  \printnames{author}%
  \par%
  \newblock%
  {%
    \footnotesize\itshape%
    \usebibmacro{journal}%
  }
  \par\vspace{0.3\baselineskip}
}
\newcommand*{\boldname}[3]{%
  \def\lastname{#1}%
  \def\firstname{#2}%
  \def\firstinit{#3}}
\renewcommand{\mkbibnamegiven}[1]{%
  \ifboolexpr{ ( test {\ifdefequal{\firstname}{\namepartgiven}} or test {\ifdefequal{\firstinit}{\namepartgiven}} ) and test {\ifdefequal{\lastname}{\namepartfamily}} }
  {\mkbibbold{#1}}{#1}%
}
\renewcommand{\mkbibnamefamily}[1]{%
  \ifboolexpr{ ( test {\ifdefequal{\firstname}{\namepartgiven}} or test {\ifdefequal{\firstinit}{\namepartgiven}} ) and test {\ifdefequal{\lastname}{\namepartfamily}} }
  {\mkbibbold{#1}}{#1}%
}
\boldname{Smith}{John}{}
\begin{document}
    \nocite{*}
    \printbibliography[type={article}]
\end{document}

Answer 1

You can use the approach from Bold certain authors and dagger other authors, which parametrises my answer to Make specific author bold using biblatex.

This approach requires Biber instead of BibTeX. Note that breakable underlining is very tricky in LaTeX. The best solution for underlining that I'm aware of is Marcel Krüger's lua-ul package (see e.g. Underline part of a word while preserving kerning), which requires LuaLaTeX.

\documentclass{article}
\usepackage{lua-ul}
\usepackage[style=alphabetic, maxnames=99, sorting=ydnt, backend=biber]{biblatex}
\makeatletter
\def\nhblx@bibfile@name{\jobname -nhblx.bib}
\newwrite\nhblx@bibfile
\immediate\openout\nhblx@bibfile=\nhblx@bibfile@name
\immediate\write\nhblx@bibfile{%
  @comment{Auto-generated file}\blx@nl}
\newcounter{nhblx@name}
\setcounter{nhblx@name}{0}
\newcommand*{\nhblx@writenametobib}[2]{%
  \ifcsundef{nhblx@#1list}
    {\csdef{nhblx@#1list}{}}
    {}%
  \stepcounter{nhblx@name}%
  \edef\nhblx@tmp@nocite{%
    \noexpand\AfterPreamble{%
      \noexpand\setbox0\noexpand\vbox{%
        \noexpand\def\noexpand\nhblx@listname{nhblx@#1list}%
        \noexpand\nhblx@getmethehash{nhblx@name@\the\value{nhblx@name}}}}%
  }%
  \nhblx@tmp@nocite
  \immediate\write\nhblx@bibfile{%
    @misc{nhblx@name@\the\value{nhblx@name}, author = {\unexpanded{#2}}, %
          options = {dataonly=true},}%
  }%
}
\AtEndDocument{%
  \closeout\nhblx@bibfile}
\addbibresource{\nhblx@bibfile@name}
\DeclareNameFormat{nhblx@hashextract}{%
  \xifinlistcs{\thefield{hash}}{\nhblx@listname}
    {}
    {\listcsxadd{\nhblx@listname}{\thefield{hash}}}}
\DeclareCiteCommand{\nhblx@getmethehash}
  {}
  {\typeout{\nhblx@listname}\printnames[nhblx@hashextract][1-999]{author}}
  {}
  {}
\newcommand{\markname}[1]{\forcsvlist{\nhblx@writenametobib{#1}}}
\newcommand{\resetmark}[1]{\csdef{nhblx@#1list}{}}
\newcommand*{\ifnamemarked}[1]{%
  \xifinlistcs{\thefield{hash}}{nhblx@#1list}}
\makeatother
\newcommand*{\nameformatter}[1]{%
  \ifnamemarked{bold}
    {\mkbibbold{#1}}
    {\ifnamemarked{underline}
       {\underLine{#1}}
       {#1}}}
\DeclareNameWrapperFormat{nameformatter}{%
  \renewcommand*{\mkbibcompletename}{\nameformatter}%
  #1}
\DeclareNameWrapperAlias{sortname}{default}
\DeclareNameWrapperAlias{default}{nameformatter}
\markname{bold}{John Smith}
\markname{underline}{Jane Doe}
\begin{filecontents}{\jobname.bib}
@article{article1,
  author  = {Smith, John and Doe, Jane and Foo, Bar},
  title   = {Title},
  journal = {Journal},
}
@article{article2,
  author  = {Smith, John and Billy, Bob},
  title   = {Title2},
  journal = {Journal2},
}
\end{filecontents}
\addbibresource{\jobname.bib}
\begin{document}
\nocite{*}
\printbibliography
\end{document}