todonotes - inline enumerate environments: Trying to bypass with marginnotes and ifinalign@

Question

I can't make use of todonotes (or marginnote but this isn't in the MWE because I don't think I have the prerequisites setup for this correctly) in an inline enumerated list.

I think I am getting the margin par error because I am in an align environment (maybe I am wrong here) I tried to augment my function with a check for the align environment so that I could provide an alternative to switch to marginnote but this didn't work.

Actually, this align check won't even compile so I have had to comment it out.

I don't know if this makes any difference, but in my non-MWE example this new command is in a cls file, and as you can see below I have tried with and without the \makeatletter/

\documentclass{article}

\usepackage{expl3}
\usepackage{xparse}
\usepackage{xpatch} 
\usepackage{letltxmacro}
\usepackage{amsmath}
\usepackage{todonotes}
\usepackage{marginnote}
\usepackage{enumerate}
\usepackage[shortlabels,inline]{enumitem}

%\makeatletter
\DeclareDocumentCommand{\TODOblock}{ O{@general} +m }
{
    \ifdefined\HCode    
        \textbf{\textbf{(NOTE: #2)}}
    \else
        %\IfNoValueF {#2} { lightslategray }
        \todo[inline,color=#1]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}
    \fi
}

\DeclareDocumentCommand{\TODOnote}{ O{@general} +m }
{
    \ifdefined\HCode    
        \textbf{\textbf{(NOTE: #2)}}
    \else
        %\ifinalign@
        %   TEXT%\marginnote[size=\scriptsize,color=#1]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}
        %\else
            \todo[size=\scriptsize,color=orange]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}
        %\fi
    \fi
}
%\makeatother

\begin{document}
    Hi heres a list \TODOnote{Of course I can do this}
    \begin{enumerate}
        \item an item \TODOnote{I can do this}
        \item next item
    \end{enumerate}

    Hi heres a list that is inline
    \begin{enumerate*}
        \item an item
        \item next item %\TODOnote{I can't do this}
    \end{enumerate*}
\end{document}

UPDATE In response to an answer that seems to have been removed, I tried nesting my custom TODO in a marginpar i.e.: \marginnote{\todo[inline,size=\scriptsize,color=orange]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}} but this doesn't align the boxes well when there are a lot of comments virtually stacked upon each other. This did get around the align problem, but the align detection still doesn't work, so I can't make use of this possibility even specifically for the limited occurrences of the align environments.

UPDATE 2 This answer that was removed also proposed a work around of using an inline version. I would be fine with this as a limited work around in the few align environments I have, but this still hinges on the \ifinalign@ structure working...

Answer 1

\ifinalign@ has nothing to do with enumerate*. This environment uses boxes for avoiding untimely line breaks, so the \todo command ends up in a forbidden planet (it must be at the outer level).

A possible solution is to check whether the \todo note is in a bad place with \ifinner and delay its working when the box ends. One needs to jump up two levels, though.

\documentclass{article}

\usepackage{expl3}
\usepackage{xparse}
\usepackage{xpatch} 
\usepackage{letltxmacro}
\usepackage{amsmath}
\usepackage{todonotes}
\usepackage{marginnote}
\usepackage{enumerate}
\usepackage[shortlabels,inline]{enumitem}

\NewDocumentCommand{\TODOblock}{ O{@general} +m }{%
  \ifdefined\HCode    
    \textbf{\textbf{(NOTE: #2)}}
  \else
    \todo[inline,color=#1]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}
  \fi
}

\NewDocumentCommand{\TODOnote}{ O{@general} +m }{%
  \ifdefined\HCode    
    \textbf{\textbf{(NOTE: #2)}}
  \else
    \ifinner
      \gdef\thisnote{%
        \todo[size=\scriptsize,color=orange]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}%
      }\aftergroup\aftergroup\aftergroup\thisnote
    \else
      \todo[size=\scriptsize,color=orange]{\unexpanded{\unexpanded{\textbf{#1:\\}#2}}}%
    \fi
  \fi
}

\begin{document}
Hi heres a list \TODOnote{Of course I can do this}
\begin{enumerate}

\item an item \TODOnote{I can do this}
\item next item

\end{enumerate}

Hi heres a list that is inline
\begin{enumerate*}

\item an item

\item next item\TODOnote{I can't do this}

\end{enumerate*}
\end{document}