The following example outputs show what happens with and without the \unskip's in the code.
Also I am adding two other examples made by the same code, one in 2012 and one just now. Note the extensions to the right of each row. They are absent in the older version.
The example code follows here:
The example code follows here:
% Switching on attribute being present (even if empty) or absent.
\def\doifexistattribute#1#2{\doifnot{\xmlattdef{#1}{#2}{__NOT__}}{__NOT__}}%{#3}
% Translate attribute: #1 = node, #2 = category #3 = attribute #4 = default value.
\def\xlat#1#2#3#4{\xmlvalue{#2}{\xmlatt{#1}{#3}}{#4}}
% Setup parameter to attribute.
% #1 = node, #2 = setup, #3 = param, #4 = attrib, #5 = category, #6 = default.
\def\setupToAttribute#1#2#3#4#5#6{%
% Only executed if attribute is present.
\doifexistattribute{#1}{#4}%
% Attribute is present but category can be empty.
{\doifelse{#5}{\empty}%
{\doifelse{\xmlatt{#1}{#4}}{\empty}%
{#2[#3=#6]}% attribute present but empty then take default
{#2[#3=\xmlatt{#1}{#4}]}% attribute has content
}%
{#2[#3=\xlat{#1}{#5}{#4}{#6}]}% translate from category
}%
}
% Setup flag (an TeX-if) from attribute values on,off,no,yes,true,false.
% #1=node #2=flag: execute \attributetrue or \attributefalse
\def\setFlagToAttribute#1#2{%
\doifexistattribute{#1}{#2}%
{%
\doifinset{\xmlatt{#1}{#2}}{on,yes,true}{\csname#2true\endcsname}%
\doifinset{\xmlatt{#1}{#2}}{off,no,false}{\csname#2false\endcsname}%
}%
}
\startxmlsetups xmlcommon
\xmlsetsetup{\xmldocument}{error|store|restore|include
|table|tr|td|tbody
}{xmlcommon:*}
\stopxmlsetups
\xmlregistersetup{xmlcommon}
% Place at top/middle(default)/bottom location.
\def\startlocationbox#1{%
\let\templocation\relax
\doif{\xmlatt{#1}{location}}{top}{\def\templocation{\vtop}}%
\doif{\xmlatt{#1}{location}}{middle}{\def\templocation{\vcenter}}%
\doif{\xmlatt{#1}{location}}{center}{\def\templocation{\vcenter}}%
\doif{\xmlatt{#1}{location}}{bottom}{\def\templocation{\vbox}}%
\templocation\bgroup\ifx\templocation\relax\else\vss\fi
}
\let\stoplocationbox\egroup
\def\setupframeparameters#1#2{%
% color
% Always set background to color if backgroundcolor is set.
\doifnot{\xmlatt{#1}{bgcolor}}{\empty}{#2[background=color]}%
% But it can be overridden.
\doifnot{\xmlatt{#1}{background}}{\empty}{#2[background=\xmlatt{#1}{background}]}%
\setupToAttribute{#1}{#2}{foregroundcolor}{color}{}{darkblue}%
\setupToAttribute{#1}{#2}{backgroundcolor}{bgcolor}{}{green}%
% frame
\doifnot{\xmlatt{#1}{frame}}{\empty}%
{#2[frame=off]\setframeparts{\xmlatt{#1}{frame}}{#2}}%
\setupToAttribute{#1}{#2}{framecolor}{framecolor}{}{black}%
\setupToAttribute{#1}{#2}{corner}{corner}{}{rectangular}%
\setupToAttribute{#1}{#2}{radius}{radius}{}{0.5ex}%
\setupToAttribute{#1}{#2}{backgroundcorner}{bgcorner}{}{rectangular}%
\setupToAttribute{#1}{#2}{backgroundradius}{bgradius}{}{0.5ex}%
% dimensions
\setupToAttribute{#1}{#2}{rulethickness}{rulethickness}{}{3pt}%
\doifnot{\xmlatt{#1}{height}}{\empty}%
{#2[height=\NumberCollect{"\xmlattdef{#1}{height}{fit}","\the\makeupheight"}]}%
\doifnot{\xmlatt{#1}{width}}{\empty}%
{#2[width=\NumberCollect{"\xmlattdef{#1}{width}{fit}","\the\textwidth"}]}%
% alignment
\setupToAttribute{#1}{#2}{strut}{strut}{}{on}%
\setupToAttribute{#1}{#2}{align}{align}{html}{normal}%
\setupToAttribute{#1}{#2}{align}{valign}{html}{lohi}%
}
% Setups for tables with xtable.
\def\setupxtableparameters#1{%
\setupframeparameters{#1}{\setupxtable}%
\setupToAttribute{#1}{\setupxtable}{foregroundstyle}{style}{style}{\tf}%
\setupToAttribute{#1}{\setupxtable}{offset}{cellpadding}{}{0pt}%
\setupToAttribute{#1}{\setupxtable}{columndistance}{cellspacing}{}{0pt}%
\setupToAttribute{#1}{\setupxtable}{spaceinbetween}{rowspacing}{}{0pt}%
\setupToAttribute{#1}{\setupxtable}{option}{option}{}{}%
}
\startxmlsetups xmlcommon:table
\bgroup
\xmlstripanywhere{#1}{.}
\setupxtable[% Setup defaults
leftmargindistance=0pt,rightmargindistance=0pt,
offset=2pt,height=fit,width=fit,
align={center,lohi},columndistance=0pt]
\setupxtableparameters{#1}
\startlocationbox{#1}
\startembeddedxtable\xmlflush{#1}\stopembeddedxtable
\stoplocationbox
\egroup
\stopxmlsetups
\startxmlsetups xmlcommon:tbody
\xmlstripanywhere{#1}{.}
\bgroup
\setupxtableparameters{#1}
\startxtablebody
\xmlflush{#1}
\stopxtablebody
\egroup
\stopxmlsetups
\startxmlsetups xmlcommon:tr
\unskip
\xmlstripanywhere{#1}{.}
\unskip
\bgroup
\unskip
\setupxtableparameters{#1}
\unskip
\startxrow
\unskip
=\xmlflush{#1}
\stopxrow
\egroup
\unskip
\stopxmlsetups
\startxmlsetups xmlcommon:td
\unskip
\xmlstrip{#1}{.}
\bgroup
\setupxtableparameters{#1}
\startxcell[nc=\xmlattdef{#1}{colspan}{1},nr=\xmlattdef{#1}{rowspan}{1}]
\xmlflush{#1}
\stopxcell
\egroup
\stopxmlsetups
\starttext
\startbuffer[the-table]
<?xml version="1.0" encoding="UTF-8"?>
<root>
<table>
<tbody>
<tr><td>A</td></tr>
<tr><td>B</td></tr>
<tr><td>C</td></tr>
<tr><td>D</td></tr>
</tbody>
</table>
</root>
\stopbuffer
\midaligned{\xmlprocessbuffer{root}{the-table}{}}
\blank
The equalsign (=) is added to \type{\startxmlsetups xmlcommon:tr} in order to show the spurious whitespace injected.
\stoptext