LaTeX writer: better fix for colspecs for multicolumn table.

Improves on the last commit; closes #8831.

3 files changed, 61 insertions, 41 deletions

diff --git a/src/Text/Pandoc/Writers/LaTeX/Table.hs b/src/Text/Pandoc/Writers/LaTeX/Table.hs
index 6ebcaa559..1d9b117ca 100644
--- a/src/Text/Pandoc/Writers/LaTeX/Table.hs
+++ b/src/Text/Pandoc/Writers/LaTeX/Table.hs
@@ -47,6 +47,11 @@ tableToLaTeX :: PandocMonad m
 tableToLaTeX inlnsToLaTeX blksToLaTeX tbl = do
   let (Ann.Table (ident, _, _) caption specs thead tbodies tfoot) = tbl
   CaptionDocs capt captNotes <- captionToLaTeX inlnsToLaTeX caption ident
+  let isSimpleTable = all (all isSimpleCell) $ mconcat
+                      [ headRows thead
+                      , concatMap bodyRows tbodies
+                      , footRows tfoot
+                      ]
   let removeNote (Note _) = Span ("", [], []) []
       removeNote x        = x
   let colCount = ColumnCount $ length specs
@@ -56,7 +61,7 @@ tableToLaTeX inlnsToLaTeX blksToLaTeX tbl = do
   -- making the caption part of the first head. The downside is that we must
   -- duplicate the header rows for this.
   head' <- do
-    let mkHead = headToLaTeX blksToLaTeX colCount
+    let mkHead = headToLaTeX blksToLaTeX isSimpleTable colCount
     case (not $ isEmpty capt, not $ isEmptyHead thead) of
       (False, False) -> return "\\toprule\\noalign{}"
       (False, True)  -> mkHead thead
@@ -66,20 +71,21 @@ tableToLaTeX inlnsToLaTeX blksToLaTeX tbl = do
         firsthead <- mkHead thead
         repeated  <- mkHead (walk removeNote thead)
         return $ capt $$ firsthead $$ "\\endfirsthead" $$ repeated
-  rows' <- mapM (rowToLaTeX blksToLaTeX colCount BodyCell) $
+  rows' <- mapM (rowToLaTeX blksToLaTeX isSimpleTable colCount BodyCell) $
                 mconcat (map bodyRows tbodies)
   foot' <- if isEmptyFoot tfoot
            then pure empty
            else do
-             lastfoot <- mapM (rowToLaTeX blksToLaTeX colCount BodyCell) $
-                              footRows tfoot
+             lastfoot <- mapM
+                (rowToLaTeX blksToLaTeX isSimpleTable colCount BodyCell) $
+                footRows tfoot
              pure $ "\\midrule\\noalign{}" $$ vcat lastfoot
   modify $ \s -> s{ stTable = True }
   notes <- notesToLaTeX <$> gets stNotes
   beamer <- gets stBeamer
   return
     $  "\\begin{longtable}[]" <>
-          braces ("@{}" <> colDescriptors tbl <> "@{}")
+          braces ("@{}" <> colDescriptors isSimpleTable tbl <> "@{}")
           -- the @{} removes extra space at beginning and end
     $$ head'
     $$ "\\endhead"
@@ -102,20 +108,26 @@ tableToLaTeX inlnsToLaTeX blksToLaTeX tbl = do
     $$ captNotes
     $$ notes
 
+isSimpleCell :: Ann.Cell -> Bool
+isSimpleCell (Ann.Cell _ _ (Cell _attr _align _rowspan _colspan blocks)) =
+  case blocks of
+    [Para _]  -> True
+    [Plain _] -> True
+    []        -> True
+    _         -> False
+
+
+
 -- | Total number of columns in a table.
 newtype ColumnCount = ColumnCount Int
 
 -- | Creates column descriptors for the table.
-colDescriptors :: Ann.Table -> Doc Text
-colDescriptors (Ann.Table _attr _caption specs thead tbodies tfoot) =
+colDescriptors :: Bool -> Ann.Table -> Doc Text
+colDescriptors isSimpleTable
+               (Ann.Table _attr _caption specs _thead _tbodies _tfoot) =
   let (aligns, widths) = unzip specs
 
       defaultWidthsOnly = all (== ColWidthDefault) widths
-      isSimpleTable = all (all isSimpleCell) $ mconcat
-                      [ headRows thead
-                      , concatMap bodyRows tbodies
-                      , footRows tfoot
-                      ]
 
       relativeWidths = if defaultWidthsOnly
                        then replicate (length specs)
@@ -136,13 +148,6 @@ colDescriptors (Ann.Table _attr _caption specs thead tbodies tfoot) =
       ((numcols - 1) * 2)
       width
 
-    isSimpleCell (Ann.Cell _ _ (Cell _attr _align _rowspan _colspan blocks)) =
-      case blocks of
-        [Para _]  -> True
-        [Plain _] -> True
-        []        -> True
-        _         -> False
-
     toRelWidth ColWidthDefault = 0
     toRelWidth (ColWidth w)    = w
 
@@ -188,24 +193,29 @@ type BlocksWriter m = [Block] -> LW m (Doc Text)
 
 headToLaTeX :: PandocMonad m
             => BlocksWriter m
+            -> Bool
             -> ColumnCount
             -> Ann.TableHead
             -> LW m (Doc Text)
-headToLaTeX blocksWriter colCount (Ann.TableHead _attr headerRows) = do
+headToLaTeX blocksWriter isSimpleTable
+            colCount (Ann.TableHead _attr headerRows) = do
   rowsContents <-
-    mapM (rowToLaTeX blocksWriter colCount HeaderCell . headerRowCells)
+    mapM (rowToLaTeX blocksWriter isSimpleTable
+           colCount HeaderCell . headerRowCells)
          headerRows
   return ("\\toprule\\noalign{}" $$ vcat rowsContents $$ "\\midrule\\noalign{}")
 
 -- | Converts a row of table cells into a LaTeX row.
 rowToLaTeX :: PandocMonad m
            => BlocksWriter m
+           -> Bool
            -> ColumnCount
            -> CellType
            -> [Ann.Cell]
            -> LW m (Doc Text)
-rowToLaTeX blocksWriter colCount celltype row = do
-  cellsDocs <- mapM (cellToLaTeX blocksWriter colCount celltype) (fillRow row)
+rowToLaTeX blocksWriter isSimpleTable colCount celltype row = do
+  cellsDocs <- mapM (cellToLaTeX blocksWriter isSimpleTable
+                      colCount celltype) (fillRow row)
   return $ hsep (intersperse "&" cellsDocs) <> " \\\\"
 
 -- | Pads row with empty cells to adjust for rowspans above this row.
@@ -280,11 +290,12 @@ displayMathToInline x                    = x
 
 cellToLaTeX :: PandocMonad m
             => BlocksWriter m
+            -> Bool
             -> ColumnCount
             -> CellType
             -> Ann.Cell
             -> LW m (Doc Text)
-cellToLaTeX blockListToLaTeX colCount celltype annotatedCell = do
+cellToLaTeX blockListToLaTeX isSimpleTable colCount celltype annotatedCell = do
   let (Ann.Cell specs colnum cell) = annotatedCell
   let colWidths = NonEmpty.map snd specs
   let hasWidths = NonEmpty.head colWidths /= ColWidthDefault
@@ -329,7 +340,8 @@ cellToLaTeX blockListToLaTeX colCount celltype annotatedCell = do
   let inMultiColumn x = case colspan of
                           (ColSpan 1) -> x
                           (ColSpan n) ->
-                            let colDescr = multicolumnDescriptor align
+                            let colDescr = multicolumnDescriptor isSimpleTable
+                                                                 align
                                                                  colWidths
                                                                  colCount
                                                                  colnum
@@ -346,12 +358,14 @@ cellToLaTeX blockListToLaTeX colCount celltype annotatedCell = do
   return . inMultiColumn . inMultiRow $ result
 
 -- | Returns the width of a cell spanning @n@ columns.
-multicolumnDescriptor :: Alignment
+multicolumnDescriptor :: Bool
+                      -> Alignment
                       -> NonEmpty ColWidth
                       -> ColumnCount
                       -> Ann.ColNumber
                       -> Text
-multicolumnDescriptor align
+multicolumnDescriptor isSimpleTable
+  align
   colWidths
   (ColumnCount numcols)
   (Ann.ColNumber colnum) =
@@ -364,13 +378,19 @@ multicolumnDescriptor align
       -- no column separators at beginning of first and end of last column.
       skipColSep = "@{}" :: String
   in T.pack $
-     printf "%s>{%s\\arraybackslash}p{(\\columnwidth - %d\\tabcolsep) * \\real{%0.4f} + %d\\tabcolsep}%s"
-            (if colnum == 0 then skipColSep else "")
-            (T.unpack (alignCommand align))
-            (2 * (numcols - 1))
-            width
-            (2 * (colspan - 1))
-            (if colnum + colspan >= numcols then skipColSep else "")
+     if isSimpleTable
+        then printf "%s%s%s"
+              (if colnum == 0 then skipColSep else "")
+              (T.unpack (colAlign align))
+              (if colnum + colspan >= numcols then skipColSep else "")
+
+        else printf "%s>{%s\\arraybackslash}p{(\\columnwidth - %d\\tabcolsep) * \\real{%0.4f} + %d\\tabcolsep}%s"
+              (if colnum == 0 then skipColSep else "")
+              (T.unpack (alignCommand align))
+              (2 * (numcols - 1))
+              width
+              (2 * (colspan - 1))
+              (if colnum + colspan >= numcols then skipColSep else "")
 
 -- | Perform a conversion, assuming that the context is a minipage.
 inMinipage :: Monad m => LW m a -> LW m a
diff --git a/test/tables/planets.latex b/test/tables/planets.latex
index ac7b7d911..8b013e3a8 100644
--- a/test/tables/planets.latex
+++ b/test/tables/planets.latex
@@ -1,14 +1,14 @@
 \begin{longtable}[]{@{}cclrrrrrrrrl@{}}
 \caption{Data about the planets of our solar system.}\tabularnewline
 \toprule\noalign{}
-\multicolumn{2}{@{}>{\centering\arraybackslash}p{(\columnwidth - 22\tabcolsep) * \real{0.0000} + 2\tabcolsep}}{%
+\multicolumn{2}{@{}c}{%
 } & Name & Mass (10\^{}24kg) & Diameter (km) & Density (kg/m\^{}3) & Gravity
 (m/s\^{}2) & Length of day (hours) & Distance from Sun (10\^{}6km) & Mean
 temperature (C) & Number of moons & Notes \\
 \midrule\noalign{}
 \endfirsthead
 \toprule\noalign{}
-\multicolumn{2}{@{}>{\centering\arraybackslash}p{(\columnwidth - 22\tabcolsep) * \real{0.0000} + 2\tabcolsep}}{%
+\multicolumn{2}{@{}c}{%
 } & Name & Mass (10\^{}24kg) & Diameter (km) & Density (kg/m\^{}3) & Gravity
 (m/s\^{}2) & Length of day (hours) & Distance from Sun (10\^{}6km) & Mean
 temperature (C) & Number of moons & Notes \\
@@ -16,7 +16,7 @@ temperature (C) & Number of moons & Notes \\
 \endhead
 \bottomrule\noalign{}
 \endlastfoot
-\multicolumn{2}{@{}>{\centering\arraybackslash}p{(\columnwidth - 22\tabcolsep) * \real{0.0000} + 2\tabcolsep}}{%
+\multicolumn{2}{@{}c}{%
 \multirow{4}{*}{Terrestrial planets}} & Mercury & 0.330 & 4,879 & 5427 & 3.7 &
 4222.6 & 57.9 & 167 & 0 & Closest to the Sun \\
 & & Venus & 4.87 & 12,104 & 5243 & 8.9 & 2802.0 & 108.2 & 464 & 0 & \\
@@ -29,7 +29,7 @@ planet \\
 & \multirow{2}{*}{Ice giants} & Uranus & 86.8 & 51,118 & 1271 & 8.7 & 17.2 &
 2872.5 & -195 & 27 & \\
 & & Neptune & 102 & 49,528 & 1638 & 11.0 & 16.1 & 4495.1 & -200 & 14 & \\
-\multicolumn{2}{@{}>{\centering\arraybackslash}p{(\columnwidth - 22\tabcolsep) * \real{0.0000} + 2\tabcolsep}}{%
+\multicolumn{2}{@{}c}{%
 Dwarf planets} & Pluto & 0.0146 & 2,370 & 2095 & 0.7 & 153.3 & 5906.4 & -225 & 5
 & Declassified as a planet in 2006. \\
 \end{longtable}
diff --git a/test/tables/students.latex b/test/tables/students.latex
index 802b00c60..f20aa027c 100644
--- a/test/tables/students.latex
+++ b/test/tables/students.latex
@@ -20,15 +20,15 @@ Name
 \endhead
 \bottomrule\noalign{}
 \endlastfoot
-\multicolumn{2}{@{}>{\raggedright\arraybackslash}p{(\columnwidth - 2\tabcolsep) * \real{1.0000} + 2\tabcolsep}@{}}{%
+\multicolumn{2}{@{}l@{}}{%
 Computer Science} \\
 3741255 & Jones, Martha \\
 4077830 & Pierce, Benjamin \\
 5151701 & Kirk, James \\
-\multicolumn{2}{@{}>{\raggedright\arraybackslash}p{(\columnwidth - 2\tabcolsep) * \real{1.0000} + 2\tabcolsep}@{}}{%
+\multicolumn{2}{@{}l@{}}{%
 Russian Literature} \\
 3971244 & Nim, Victor \\
-\multicolumn{2}{@{}>{\raggedright\arraybackslash}p{(\columnwidth - 2\tabcolsep) * \real{1.0000} + 2\tabcolsep}@{}}{%
+\multicolumn{2}{@{}l@{}}{%
 Astrophysics} \\
 4100332 & Petrov, Alexandra \\
 4100332 & Toyota, Hiroko \\