incorrect vertical-align settings with tabular

[xworld21]

The following

\documentclass{article}
\usepackage{array}
\begin{document}
    \begin{tabular}{c|p{2cm}|c}
         a&  a very long line, enough to wrap (p) & b
    \end{tabular}

    \begin{tabular}{c|m{2cm}|c}
         a&  a very long line, enough to wrap (m) & b
    \end{tabular}

    \begin{tabular}{c|b{2cm}|c}
         a&  a very long line, enough to wrap (b) & b
    \end{tabular}
\end{document}

should look like

but it comes out as

Even after temporarily setting .ltx_td { vertical-align: baseline !important; }, you get

There are three bugs here:

1. The width of p{2cm} gets lost.
2. All cells should be vertical-align: baseline, no matter what.
3. The content of the column m should have ltx_align_middle instead of ltx_align_top.

Changing all three manually gives you

[xworld21]

Quick note, the following (S)CSS should work 99% of the times:

.ltx_th, .ltx_td {
  vertical-align: baseline;

  @each $i in top middle bottom {
    &.ltx_align_#{$i}>* {
      vertical-align: #{$i};
    }
  }

  @supports (baseline-source: first) {
    &.ltx_align_top>* {
      vertical-align: baseline;
      baseline-source: first;
    }

    &.ltx_align_bottom>* {
      vertical-align: baseline;
      baseline-source: last;
    }
  }
}

...and it can be probably simplified, because the child >* is already correct, it's actually only the middle case that needs handling. However, this feels fragile against all the stuff that happens in insertBlock, and specifically when vertical boxes are nested.

The best solution is to set vattach=middle right when creating the box at

LaTeXML/lib/LaTeXML/Package/array.sty.ltxml

Line 30 in d81e955

$LaTeXML::BUILD_TEMPLATE->addColumn(before => Tokens(T_CS('\vtop'), T_BEGIN), #Tokens(T_BEGIN),

Quickest route that comes to mind is adding \lx@vbox@middle in addition to \vtop, \vbox so that insertBlock can do its magic undisturbed.