Use `\cite` and `\bibitem` to link up citations, even with citeproc.

See #9031 and discussion in #9020. This will give us better
accessibility; when tagging is enabled, the citation can be
linked to the bibliography entry.

This changes some of the details of the layout and the default
template. We now make CSLReferences a special enumitem list
that will contain `\bibitem`s.

Internal links inside citations to ids beginning in `ref-` are
put inside a `\cite` instead of `\hyperref`.

Closes #9031.

3 files changed, 54 insertions, 35 deletions

diff --git a/data/templates/default.latex b/data/templates/default.latex
index e2cfce1f1..c177c00e8 100644
--- a/data/templates/default.latex
+++ b/data/templates/default.latex
@@ -335,24 +335,28 @@ $if(pagestyle)$
 \pagestyle{$pagestyle$}
 $endif$
 $if(csl-refs)$
+% definitions for citeproc citations
+\NewDocumentCommand\citeproctext{}{}
+\NewDocumentCommand\citeproc{mm}{%
+  \begingroup\def\citeproctext{#2}\cite{#1}\endgroup}
+% avoid brackets around text for \cite:
+\makeatletter
+ \def\@biblabel#1{}
+ \def\@cite#1#2{{#1\if@tempswa , #2\fi}}
+\makeatother
 \newlength{\cslhangindent}
 \setlength{\cslhangindent}{1.5em}
 \newlength{\csllabelwidth}
 \setlength{\csllabelwidth}{3em}
-\newlength{\cslentryspacingunit} % times entry-spacing
-\setlength{\cslentryspacingunit}{\parskip}
-\newenvironment{CSLReferences}[2] % #1 hanging-ident, #2 entry spacing
- {% don't indent paragraphs
-  \setlength{\parindent}{0pt}
-  % turn on hanging indent if param 1 is 1
-  \ifodd #1
-  \let\oldpar\par
-  \def\par{\hangindent=\cslhangindent\oldpar}
-  \fi
-  % set entry spacing
-  \setlength{\parskip}{#2\cslentryspacingunit}
- }%
- {}
+\newlength{\cslentryspacing}
+\setlength{\cslentryspacing}{0em}
+\usepackage{enumitem}
+\newlist{CSLReferences}{itemize}{1}
+\setlist[CSLReferences]{label={},
+  leftmargin=\cslhangindent,
+  itemindent=-1\cslhangindent,
+  parsep=\parskip,
+  itemsep=\cslentryspacing}
 \usepackage{calc}
 \newcommand{\CSLBlock}[1]{#1\hfill\break}
 \newcommand{\CSLLeftMargin}[1]{\parbox[t]{\csllabelwidth}{#1}}
diff --git a/src/Text/Pandoc/Writers/LaTeX.hs b/src/Text/Pandoc/Writers/LaTeX.hs
index d12890bd5..bdfa96c1a 100644
--- a/src/Text/Pandoc/Writers/LaTeX.hs
+++ b/src/Text/Pandoc/Writers/LaTeX.hs
@@ -339,22 +339,30 @@ blockToLaTeX (Div (identifier,classes,kvs) bs) = do
                then do
                  modify $ \st -> st{ stHasCslRefs = True }
                  inner <- blockListToLaTeX bs
-                 return $ "\\begin{CSLReferences}" <>
-                          (if "hanging-indent" `elem` classes
-                              then braces "1"
-                              else braces "0") <>
-                          (case lookup "entry-spacing" kvs of
-                             Nothing -> braces "0"
-                             Just s  -> braces (literal s))
+                 return $ (if "hanging-indent" `notElem` classes
+                               then "\\setlength{\\cslhangindent}{0em}"
+                               else mempty)
+                          $$ ("\\setlength{\\cslentryspacing}" <> braces
+                               (case lookup "entry-spacing" kvs of
+                                  Nothing -> "0em"
+                                  Just s  -> (literal s <> "\\baselineskip")))
+                          $$ "\\begin{CSLReferences}"
                           $$ inner
                           $+$ "\\end{CSLReferences}"
                else blockListToLaTeX bs
   modify $ \st -> st{ stIncremental = oldIncremental }
-  linkAnchor <- hypertarget identifier
-  let wrapNotes txt = if beamer && "notes" `elem` classes
-                         then "\\note" <> braces txt -- speaker notes
-                         else linkAnchor $$ txt
-  wrapNotes <$> wrapDiv (identifier,classes,kvs) result
+  let wrap txt
+       | beamer && "notes" `elem` classes
+         = pure ("\\note" <> braces txt) -- speaker notes
+       | "ref-" `T.isPrefixOf` identifier
+         = do
+             lab <- toLabel identifier
+             pure $ ("\\bibitem" <> brackets "\\citeproctext"
+                      <> braces (literal lab)) $$ txt
+         | otherwise = do
+             linkAnchor <- hypertarget identifier
+             pure $ linkAnchor $$ txt
+  wrapDiv (identifier,classes,kvs) result >>= wrap
 blockToLaTeX (Plain lst) =
   inlineListToLaTeX lst
 -- . . . indicates pause in beamer slides
@@ -816,12 +824,14 @@ inlineToLaTeX (Subscript lst) =
 inlineToLaTeX (SmallCaps lst) =
   inCmd "textsc"<$> inlineListToLaTeX lst
 inlineToLaTeX (Cite cits lst) = do
-  st <- get
-  let opts = stOptions st
-  case writerCiteMethod opts of
-     Natbib   -> citationsToNatbib inlineListToLaTeX cits
-     Biblatex -> citationsToBiblatex inlineListToLaTeX cits
-     _        -> inlineListToLaTeX lst
+  opts <- gets stOptions
+  modify $ \st -> st{ stInCite = True }
+  res <- case writerCiteMethod opts of
+           Natbib   -> citationsToNatbib inlineListToLaTeX cits
+           Biblatex -> citationsToBiblatex inlineListToLaTeX cits
+           _        -> inlineListToLaTeX lst
+  modify $ \st -> st{ stInCite = False }
+  pure res
 
 inlineToLaTeX (Code (_,classes,kvs) str) = do
   opts <- gets stOptions
@@ -945,11 +955,14 @@ inlineToLaTeX (Link (id',_,_) txt (src,_)) =
      Just ('#', ident) -> do
         contents <- inlineListToLaTeX txt
         lab <- toLabel ident
+        inCite <- gets stInCite
         beamer <- gets stBeamer
         return $
-          if beamer
-             then text "\\hyperlink" <> braces (literal lab) <> braces contents
-             else text "\\hyperref" <> brackets (literal lab) <> braces contents
+          if inCite && "#ref-" `T.isPrefixOf` src
+             then "\\citeproc" <> braces (literal lab) <> braces contents
+             else if beamer
+                     then "\\hyperlink" <> braces (literal lab) <> braces contents
+                     else "\\hyperref" <> brackets (literal lab) <> braces contents
      _ -> case txt of
           [Str x] | unEscapeString (T.unpack x) == unEscapeString (T.unpack src) ->  -- autolink
                do modify $ \s -> s{ stUrl = True }
diff --git a/src/Text/Pandoc/Writers/LaTeX/Types.hs b/src/Text/Pandoc/Writers/LaTeX/Types.hs
index 97ac1dcf9..0e0582948 100644
--- a/src/Text/Pandoc/Writers/LaTeX/Types.hs
+++ b/src/Text/Pandoc/Writers/LaTeX/Types.hs
@@ -26,6 +26,7 @@ data WriterState =
   , stInHeading     :: Bool          -- ^ true if in a section heading
   , stInItem        :: Bool          -- ^ true if in \item[..]
   , stInFigure      :: Bool          -- ^ true if in figure environment
+  , stInCite        :: Bool          -- ^ true if in a Cite
   , stNotes         :: [Doc Text]    -- ^ notes in a minipage
   , stOLLevel       :: Int           -- ^ level of ordered list nesting
   , stOptions       :: WriterOptions -- ^ writer options, so they don't have to
@@ -61,6 +62,7 @@ startingState options =
   , stInMinipage = False
   , stInItem = False
   , stInFigure = False
+  , stInCite = False
   , stNotes = []
   , stOLLevel = 1
   , stOptions = options