faulty colors with pgf

[u-fischer]

colorspace sets here both pgf colors to a spot color:

\def\pgfsys@color@&spot#1{%
  \pgfsys@color@&spot@stroke{#1}%
  \pgfsys@color@&spot@fill{#1}}

But actually pgf doesn't always set both colors and if colorspace tries to handle a non-spot color as spot color you get illegal 0 CS 1 SC 0 cs 1 sc in pdf and so a broken pdf. I suggest that colorspace does at least a light weight test here:

\RequirePackage{expl3}
\ExplSyntaxOn
\pdf_uncompress:
\ExplSyntaxOff
\documentclass{article}
\usepackage{tikz,colorspace}
\ExplSyntaxOn\makeatletter
%if the color is not a spot color, color space shouldn't set it.
%this is a simple test looking if the specification starts with a /:
\cs_set:cpn {pgfsys@color@&spot@fill} #1{%
  \spc@getir{\string\color@pgffillcolor}%
  \tl_if_head_eq_charcode:fNTF {\spc@ir}/
  {
    \pgfsysprotocol@literal{\spc@ir\space cs}%
    \pgfsysprotocol@literal{#1~sc}
  }
  {
    \PackageWarning{colorspace}{color@pgffillcolor~is~not~a~spot~color,~ignored}{}
  }}
  
\cs_set:cpn {pgfsys@color@&spot@stroke} #1{%
  \spc@getir{\string\color@pgfstrokecolor}%
  \tl_if_head_eq_charcode:fNTF {\spc@ir}/
   {
     \pgfsysprotocol@literal{\spc@ir\space CS}%
     \pgfsysprotocol@literal{#1~SC}
   }
   {
    \PackageWarning{colorspace}{color@pgffillcolor~is~not~a~spot~color,~ignored}{}
   }}
\ExplSyntaxOff\makeatother

\definespotcolor{myblue}{HKS 44 K}[cmyk]{1,0.5,0,0}


\begin{document}
\tikz\node[text=myblue]{abc};
\end{document}

The warning is optional but helps to debug the places. In the example it has two hits:

Package colorspace Warning: color@pgffillcolor is not a spot color, ignored on 
input line 72.


Package colorspace Warning: color@pgffillcolor is not a spot color, ignored on 
input line 72.