chemnum (2oct19)

git-svn-id: svn://tug.org/texlive/trunk@52256 c570f23f-e606-0410-a88d-b1316a301751

4 files changed, 341 insertions, 255 deletions

diff --git a/Master/texmf-dist/doc/latex/chemnum/README b/Master/texmf-dist/doc/latex/chemnum/README
index ddfa8b2331e..fd5fdfcd173 100644
--- a/Master/texmf-dist/doc/latex/chemnum/README
+++ b/Master/texmf-dist/doc/latex/chemnum/README
@@ -1,16 +1,14 @@
 --------------------------------------------------------------------------
-chemnum v1.2 2016/04/14
+chemnum v1.2c 2019/10/02
 
   a comprehensive approach for the numbering of chemical compounds
 
 --------------------------------------------------------------------------
 Clemens Niederberger
-Web:
-  v0.* https://bitbucket.org/cgnieder/chemnum/
-  v1.* https://github.com/cgnieder/chemnum
+Web:    https://github.com/cgnieder/chemnum
 E-Mail: contact@mychemistry.eu
 --------------------------------------------------------------------------
-Copyright 2011-2016 Clemens Niederberger
+Copyright 2011--2019 Clemens Niederberger
 
 This work may be distributed and/or modified under the
 conditions of the LaTeX Project Public License, either version 1.3
@@ -32,5 +30,3 @@ This work consists of the files
 - chemnum_en.tex, chemnum_en.pdf
 - README
 --------------------------------------------------------------------------
-Version 1 is a complete re-write from scratch of the `chemnum' package.
---------------------------------------------------------------------------
diff --git a/Master/texmf-dist/doc/latex/chemnum/chemnum_en.pdf b/Master/texmf-dist/doc/latex/chemnum/chemnum_en.pdf
index 4f6a1d26e58..9254c029c57 100644
--- a/Master/texmf-dist/doc/latex/chemnum/chemnum_en.pdf
+++ b/Master/texmf-dist/doc/latex/chemnum/chemnum_en.pdf
diff --git a/Master/texmf-dist/doc/latex/chemnum/chemnum_en.tex b/Master/texmf-dist/doc/latex/chemnum/chemnum_en.tex
index a5abd7365da..f6da470d1df 100644
--- a/Master/texmf-dist/doc/latex/chemnum/chemnum_en.tex
+++ b/Master/texmf-dist/doc/latex/chemnum/chemnum_en.tex
@@ -1,8 +1,36 @@
-% arara: pdflatex: { shell: on }
-%! arara: pdflatex: { shell: on }
-% arara: biber
-% arara: pdflatex
-% arara: pdflatex
+% --------------------------------------------------------------------------
+% the CHEMNUM package
+%
+%   a comprehensive approach for the numbering of chemical compounds
+%
+% --------------------------------------------------------------------------
+% Clemens Niederberger
+% --------------------------------------------------------------------------
+% https://github.org/cgnieder/chemnum/
+% contact@mychemistry.eu
+% --------------------------------------------------------------------------
+% If you have any ideas, questions, suggestions or bugs to report, please
+% feel free to contact me.
+% --------------------------------------------------------------------------
+% Copyright 2011--2019 Clemens Niederberger
+%
+% This work may be distributed and/or modified under the
+% conditions of the LaTeX Project Public License, either version 1.3
+% of this license or (at your option) any later version.
+% The latest version of this license is in
+%   http://www.latex-project.org/lppl.txt
+% and version 1.3 or later is part of all distributions of LaTeX
+% version 2005/12/01 or later.
+%
+% This work has the LPPL maintenance status `maintained'.
+%
+% The Current Maintainer of this work is Clemens Niederberger.
+% --------------------------------------------------------------------------
+% !arara: pdflatex: { shell: on , interaction: nonstopmode }
+% !arara: pdflatex: { shell: on , interaction: nonstopmode }
+% !arara: biber
+% arara: pdflatex: { interaction: nonstopmode }
+% arara: pdflatex: { interaction: nonstopmode }
 \documentclass[load-preamble+,ngerman,british,american]{cnltx-doc}
 \usepackage[utf8]{inputenc}
 \usepackage{chemnum}
@@ -47,7 +75,7 @@
     keyis,
     marginnote, midrule,
     NewDocumentCommand,
-    schemestart,schemestop,setatomsep,
+    schemestart,schemestop,setchemfig,
     theffbibliography, toprule
   } ,
   index-setup = { othercode=\footnotesize,level=\addsec },
@@ -60,11 +88,13 @@
 \usepackage{chemformula}
 \setchemformula{format=\libertineLF}
 \usepackage{chemfig,relsize}
-\setatomsep{1.78500 em}
-\setbondstyle{line width = 0.06642 em}
+\setchemfig{
+  atom sep = 1.78500 em ,
+  bond style = {line width = 0.06642 em}
+}
 \renewcommand*\printatom[1]{\textsmaller{\ensuremath{\mathsf{#1}}}}
 
-\usepackage{array,booktabs}
+\usepackage{array,booktabs,csquotes}
 
 \usepackage{graphicx}
 
@@ -112,57 +142,6 @@
 \pkg{chemgreek}~\cite{pkg:chemgreek} and the \pkg{psfrag}~\cite{pkg:psfrag}
 package.
 
-\section{News}\label{sec:news}
-The \chemnum\ package has been my first attempt to create a comprehensive
-labeling package for chemical compounds.  However, it had and has more than
-one weakness and its code was -- to be frank -- a mess.  Version~1 is now a
-complete re-write of \chemnum\ where I tried to achieve several points:
-\begin{itemize}
-  \item A cleaner code internally.
-  \item A cleaner user interface, \ie, more user macros for different tasks, a
-    unified naming of the commands and a less redundant naming of the
-    options.
-  \item Extended functionality such as sorting and compressing of sublabel
-    lists and sorting and merging of main label lists.
-\end{itemize}
-
-Although the syntax seems more or less the same at first sight quite a number
-of changes have been made that make version~1 incompatible with version~0.
-While I thought a while about maintaining backwards compatibility version~0
-was known to be in an experimental stage where everything was allowed to be
-changed at any time.  So users \emph{could} know there was a risk.  I have a
-feeling that many users nevertheless didn't realize this and may be bothered
-by this incompatibility.  So I am well aware that the update will
-inconvenience some users.  However, since version~0 won't be updated any more
-it made more sense to make a breaking update once.
-
-The same is not true for version~1.  The syntax and commands described in this
-manual will not be changed as easily and from this version on I will take care
-of backwards compatibility.
-
-For those people wanting to keep older versions: they are are still available
-from websites such as \website{ctanhg.scharrer-online.de} or
-\securewebsite{bitbucket.org/cgnieder/chemnum}.  You can also email me for an
-older version.
-
-Many commands have got a new name! The most important ones are:
-\begin{itemize}
-  \item \cs*{cmpdref}; this is now called \cs{replacecmpd}.
-  \item \cs*{cmpdinit}; this is now called \cs{initcmpd}.
-  \item \cs*{cmpdreset}; this is now called \cs{resetcmpd}.
-  \item \cs*{cmpdsetup}; this is now called \cs{setchemnum}.
-\end{itemize}
-However, there are many more changes.  Basically all options have new names
-and often do their thing slightly different from the way things have been
-before.
-
-Please note that this overall change does not mean that version~1 is version~0
-declared stable.  It is very likely that version~1 will now have quite a
-number of bugs to be fixed and probably missing features, too.  So I'd be very
-glad to receive feedback either on \chemnum's homepage
-\securewebsite{github.com/cgnieder/chemnum} or via email to
-\email{contact@mychemistry.eu}.
-
 \section{Overview over the Available Commands}\label{sec:overv-over-avail}
 
 This section lists all available commands with a brief description.  Commands
@@ -198,7 +177,7 @@ Most of the commands will be explained in a later section in more detail.
     section~\ref{sec:deta-comp-labels}.
   \command{replacecmpd}[\code{+}\oarg{options}\marg{\ac{id}}]
     A command for replacing tags in \ac{eps} files, see
-    section~\ref{sec:replacing-tags-aceps} for details.
+    section~\ref{sec:replacing-tags-eps-ps} for details.
   \command{initcmpd}[\oarg{options}\marg{list of \acp{id}}]
     Initiate compound labels.  This command can only be used in the preamble.
     It is desribed in section~\ref{sec:deta-comp-labels}.
@@ -329,7 +308,7 @@ see section~\ref{sec:chang-input-mark} for details.
   More than one label can be put inside \cs{cmpd}, separated by commas.  Then
   a list like \cmpd{a, b, c, e, g.two} is printed.
 \end{example}
-The Harvard comma (see section~\ref{sec:lang-depend-sett}) in \code{, and}
+The Harvard comma (see section~\ref{sec:lang-depend-sett}) in \enquote{\code{, and}}
 between \cmpd{e} and \cmpd{g.two} suggests that there are options to customize
 the list, see section~\ref{sec:formatting-labels} for more on this.
 
@@ -608,10 +587,14 @@ command.  They are marked with \module{replace}.
   \keybool{merge}\Module{both (l)}\Default{false}
     If set to true a list of labels is merged, \ie,
     ``\cmpd{q.five,a,q.two}'' becomes ``\cmpd[merge=true]{q.five,a,q.two}''.
-  \keyval{pre-label-code}{code}\Module{cmpd (g)}\Default
+  \keyval{pre-label-code}{code}\Module{both (g)}\Default
     Code to be inserted before a label.
-  \keyval{post-label-code}{code}\Module{cmpd (g)}\Default
+  \keyval{post-label-code}{code}\Module{both (g)}\Default
     Code to be inserted after a label.
+  \keyval{pre-main-label-code}{code}\Module{both (g)}\Default
+    \sinceversion{1.2a}Code to be inserted before a main label.
+  \keyval{post-main-label-code}{code}\Module{both (g)}\Default
+    \sinceversion{1.2a}Code to be inserted after a main label.
   \keyval{main-sub-sep}{code}\Module{both (l)}\Default{.}
     The separator symbol that is used in \cs{cmpd} to separate the \meta{main
       \ac{id}} from a \meta{sub \ac{id}}.
@@ -855,9 +838,9 @@ explicitly will overwrite the language sensitivity.  If you only want to adapt
 the separators to your language have a look at
 section~\ref{sec:lang-depend-sett}.
 
-\section{Replacing Tags in \ac{eps} or \ac{ps} Files}\label{sec:replacing-tags-aceps}
+\section{Replacing Tags in \ac{eps} or \ac{ps} Files}\label{sec:replacing-tags-eps-ps}
 
-Although it is quite possible to create rection schemes within \LaTeX\
+Although it is quite possible to create reaction schemes within \LaTeX\
 directly -- for example with the \pkg{chemfig} package~\cite{pkg:chemfig} --
 many people prefer to use a program such as \textsc{ChemDraw} for it.  In
 order to be able to use the labels with such schemes as well the following
@@ -865,11 +848,18 @@ method is usually used:
 \begin{itemize}
   \item Create the scheme and place temporary tags like \code{TMP1},
     \code{TMP2} and so on where you want the compound labels to be.
-  \item Export the scheme as \ac{eps} or \ac{ps} figure where you make sure
-    that the tags are embedded as text strings.
+  \item Export the scheme as \ac{eps} or \ac{ps} figure \emph{where you make
+      sure that the tags are embedded as text strings}.  If the tags are not
+    present as text strings they cannot be replaced.  This is a common source
+    of user problems.
   \item Include the \ac{eps} with \cs*{includegraphics}.  Right before that
     use \cs{replacecmpd} once for every temporary tag.
 \end{itemize}
+\emph{For the actual replacement please make sure that you compile with
+  \code{shell-escape} enabled.  If you compile with \code{pdflatex} you
+  probably also need \pkg{auto-pst-pdf}~\cite{pkg:auto-pst-pdf} loaded. In
+  subsequent runs load it with option \code{off} when you turned off
+  \code{shell-escape}.}
 
 \begin{commands}
   \command{replacecmpd}[\code{+}\oarg{options}\marg{\ac{id}}]
@@ -894,7 +884,7 @@ The tags now can be replaced with labels.  The result is shown in
 figure~\ref{fig:scheme-tmp-tags-replaced}.
 \begin{example}[compile,exe-with={--shell-escape},runs=1,float=htbp,caption={A scheme with
   temporary tags replaced with labels.\label{fig:scheme-tmp-tags-replaced}}]
-  % code for figure 2
+  % code for figure 2 -- compiled with shell-escape enabled
   \documentclass{standalone}
   \usepackage{graphicx,auto-pst-pdf,chemnum}
   \begin{document}
@@ -971,7 +961,7 @@ respect to the \ac{ps} box that is replaced.  This is described in
 
 \begin{example}[compile,exe-with={--shell-escape},runs=1,float=htbp,caption={A scheme with
   arbitrary tags replaced with labels.\label{fig:scheme-bla-tags-replaced}}]
-  % code for figure 4
+  % code for figure 4 -- compiled with shell-escape enabled
   \documentclass{standalone}
   \usepackage{graphicx,auto-pst-pdf,chemnum}
   \begin{document}
@@ -1025,6 +1015,11 @@ wrong please write me an email and I'll add your language or fix the wrong
 translation.
 
 \begin{table}[htbp]
+  \newcommand*\showlanguageentry[1]{%
+    #1
+    & \visualizespaces{\GetTranslationFor{#1}{chemnum-sep-two}}
+    & \visualizespaces{\GetTranslationFor{#1}{chemnum-sep-last-two}}
+  }
   \centering
   \caption{Available languages}
   \label{tab:languages}
@@ -1034,45 +1029,19 @@ translation.
       \bfseries chemnum-sep-two &
       \bfseries chemnum-sep-last-two \\
     \midrule
-      English
-        & \visualizespaces{\GetTranslationFor{English}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{English}{chemnum-sep-last-two}} \\
-      American
-        & \visualizespaces{\GetTranslationFor{American}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{American}{chemnum-sep-last-two}} \\
-      German
-        & \visualizespaces{\GetTranslationFor{German}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{German}{chemnum-sep-last-two}} \\
-      French
-        & \visualizespaces{\GetTranslationFor{French}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{French}{chemnum-sep-last-two}} \\
-      Spanish
-        & \visualizespaces{\GetTranslationFor{Spanish}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Spanish}{chemnum-sep-last-two}} \\
-      Italian
-        & \visualizespaces{\GetTranslationFor{Italian}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Italian}{chemnum-sep-last-two}} \\
-      Catalan
-        & \visualizespaces{\GetTranslationFor{Catalan}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Catalan}{chemnum-sep-last-two}} \\
-      Portuguese
-        & \visualizespaces{\GetTranslationFor{Portuguese}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Portuguese}{chemnum-sep-last-two}} \\
-      Dutch
-        & \visualizespaces{\GetTranslationFor{Dutch}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Dutch}{chemnum-sep-last-two}} \\
-      Danish
-        & \visualizespaces{\GetTranslationFor{Danish}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Danish}{chemnum-sep-last-two}} \\
-      Swedish
-        & \visualizespaces{\GetTranslationFor{Swedish}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Swedish}{chemnum-sep-last-two}} \\
-      Finnish
-        & \visualizespaces{\GetTranslationFor{Finnish}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Finnish}{chemnum-sep-last-two}} \\
-      Norwegian
-        & \visualizespaces{\GetTranslationFor{Norwegian}{chemnum-sep-two}}
-        & \visualizespaces{\GetTranslationFor{Norwegian}{chemnum-sep-last-two}} \\
+      \showlanguageentry{English} \\
+      \showlanguageentry{American} \\
+      \showlanguageentry{German} \\
+      \showlanguageentry{French} \\
+      \showlanguageentry{Spanish} \\
+      \showlanguageentry{Italian} \\
+      \showlanguageentry{Catalan} \\
+      \showlanguageentry{Portuguese} \\
+      \showlanguageentry{Dutch} \\
+      \showlanguageentry{Danish} \\
+      \showlanguageentry{Swedish} \\
+      \showlanguageentry{Finnish} \\
+      \showlanguageentry{Norwegian} \\
     \bottomrule
   \end{tabular}
 \end{table}
@@ -1173,6 +1142,55 @@ above commands are defined in terms of them:
   \NewDocumentCommand\subcmpdshowref{mm}{\chemnumshowref{#2}}
 \end{sourcecode}
 
-\end{document}
+\section{From Version~0 to Version~1}\label{sec:news}
+The \chemnum\ package has been my first attempt to create a comprehensive
+labeling package for chemical compounds.  However, it had and has more than
+one weakness and its code was -- to be frank -- a mess.  Version~1 is now a
+complete re-write of \chemnum\ where I tried to achieve several points:
+\begin{itemize}
+  \item A cleaner code internally.
+  \item A cleaner user interface, \ie, more user macros for different tasks, a
+    unified naming of the commands and a less redundant naming of the
+    options.
+  \item Extended functionality such as sorting and compressing of sublabel
+    lists and sorting and merging of main label lists.
+\end{itemize}
 
+Although the syntax seems more or less the same at first sight quite a number
+of changes have been made that make version~1 incompatible with version~0.
+While I thought a while about maintaining backwards compatibility version~0
+was known to be in an experimental stage where everything was allowed to be
+changed at any time.  So users \emph{could} know there was a risk.  I have a
+feeling that many users nevertheless didn't realize this and may be bothered
+by this incompatibility.  So I am well aware that the update will
+inconvenience some users.  However, since version~0 won't be updated any more
+it made more sense to make a breaking update once.
 
+The same is not true for version~1.  The syntax and commands described in this
+manual will not be changed as easily and from this version on I will take care
+of backwards compatibility.
+
+For those people wanting to keep older versions: they are are still available
+from websites such as \website{ctanhg.scharrer-online.de} or
+\securewebsite{bitbucket.org/cgnieder/chemnum}.  You can also email me for an
+older version.
+
+Many commands have got a new name! The most important ones are:
+\begin{itemize}
+  \item \cs*{cmpdref}; this is now called \cs{replacecmpd}.
+  \item \cs*{cmpdinit}; this is now called \cs{initcmpd}.
+  \item \cs*{cmpdreset}; this is now called \cs{resetcmpd}.
+  \item \cs*{cmpdsetup}; this is now called \cs{setchemnum}.
+\end{itemize}
+However, there are many more changes.  Basically all options have new names
+and often do their thing slightly different from the way things have been
+before.
+
+Please note that this overall change does not mean that version~1 is version~0
+declared stable.  It is very likely that version~1 will now have quite a
+number of bugs to be fixed and probably missing features, too.  So I'd be very
+glad to receive feedback either on \chemnum's homepage
+\securewebsite{github.com/cgnieder/chemnum} or via email to
+\email{contact@mychemistry.eu}.
+
+\end{document}
diff --git a/Master/texmf-dist/tex/latex/chemnum/chemnum.sty b/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
index 659378bf72a..b7d1277df49 100644
--- a/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
+++ b/Master/texmf-dist/tex/latex/chemnum/chemnum.sty
@@ -12,7 +12,7 @@
 % If you have any ideas, questions, suggestions or bugs to report, please
 % feel free to contact me.
 % --------------------------------------------------------------------------
-% Copyright 2011-2016 Clemens Niederberger
+% Copyright 2011--2019 Clemens Niederberger
 %
 % This work may be distributed and/or modified under the
 % conditions of the LaTeX Project Public License, either version 1.3
@@ -26,32 +26,41 @@
 %
 % The Current Maintainer of this work is Clemens Niederberger.
 % --------------------------------------------------------------------------
-\def\chemnumdate{2016/04/14}
-\def\chemnumversion{1.2}
-\def\chemnuminfo{a comprehensive approach for the numbering of chemical compounds}
+\RequirePackage{expl3,xparse,l3keys2e}
 
-\RequirePackage{expl3}[2016/03/28]
-\RequirePackage{xparse,l3keys2e}
+\ExplSyntaxOn
+\tl_const:Nn \c_chemnum_date_tl {2019/10/02}
+\tl_const:Nn \c_chemnum_version_number_tl {1.2}
+\tl_const:Nn \c_chemnum_version_suffix_tl {c}
+\tl_const:Nx \c_chemnum_version_tl
+  { \c_chemnum_version_number_tl \c_chemnum_version_suffix_tl }
+\tl_const:Nn \c_chemnum_info_tl
+  {a~ comprehensive~ approach~ for~ the~ numbering~ of~ chemical~ compounds}
 
 % ----------------------------------------------------------------------------
 % provide the package:
-\ProvidesExplPackage{chemnum}
-  {\chemnumdate}
-  {\chemnumversion}
-  {\chemnuminfo\space (CN)}
+\ProvidesExplPackage
+  {chemnum}
+  {\c_chemnum_date_tl}
+  {\c_chemnum_version_tl}
+  {\c_chemnum_info_tl \c_space_tl (CN)}
 
 % ----------------------------------------------------------------------------
 % required packages:
 % language support:
-\RequirePackage{translations}[2015/11/07]
+\RequirePackage{translations}
+
 % greek alphabet for the labels matching to chemmacros' selection:
-\RequirePackage{chemgreek}[2016/02/10]
+\RequirePackage{chemgreek}
 \RequirePackage{psfrag}
 
 % ----------------------------------------------------------------------------
 % messages:
 \msg_new:nnn {chemnum} {missing-label}
-  { The~ key~ `#1'~ has~ no~ label~ associated~ \msg_line_context: }
+  {
+    The~ key~ `#1' \tl_if_blank:nF {#2} {~ of~`#2'} ~ has~ no~ label~
+    associated~ \msg_line_context:
+  }
 
 \msg_new:nnn {chemnum} {erroneous-argument-combination}
   {
@@ -210,6 +219,8 @@
 \int_new:N \l__chemnum_tmpb_int
 \int_new:N \l__chemnum_tmpc_int
 
+\str_new:N \l__chemnum_tmpa_str
+
 % ----------------------------------------------------------------------------
 % variables:
 \prop_new:N \l__chemnum_label_formats_prop
@@ -227,6 +238,7 @@
 \seq_new:N \g__chemnum_defined_compounds_seq
 \seq_new:N \g__chemnum_compound_defined_subcompounds_seq
 
+\tl_const:Nn \c_chemnum_nothing_here_tl {??}
 \tl_new:N  \l__chemnum_label_format_tl
 \tl_set:Nn \l__chemnum_label_format_tl {\bfseries}
 \tl_new:N  \l__chemnum_local_label_format_tl
@@ -367,13 +379,13 @@
     sub-counter-format .groups:n = {compound,general} ,
     % label:
     pre-label-code .tl_set:N = \l__chemnum_pre_label_default_tl ,
-    pre-label-code .groups:n = {compound} ,
+    pre-label-code .groups:n = {compound,general} ,
     post-label-code .tl_set:N = \l__chemnum_post_label_default_tl ,
-    post-label-code .groups:n = {compound} ,
+    post-label-code .groups:n = {compound,general} ,
     pre-main-label-code .tl_set:N = \l__chemnum_pre_main_label_default_tl ,
-    pre-main-label-code .groups:n = {compound} ,
+    pre-main-label-code .groups:n = {compound,general} ,
     post-main-label-code .tl_set:N = \l__chemnum_post_main_label_default_tl ,
-    post-main-label-code .groups:n = {compound} ,
+    post-main-label-code .groups:n = {compound,general} ,
     main-sub-sep .tl_set:N = \l__chemnum_compound_separator_tl ,
     main-sub-sep .groups:n = {general,list} ,
     list-label-sep .tl_set:N = \l__chemnum_main_separator_tl ,
@@ -512,14 +524,15 @@
 % if the `chemnum' package is removed from the preamble
 \AtBeginDocument
   {
-    \if@filesw
-      \iow_now:Nn \@auxout
-        {
-          \providecommand\chemnum@cmpd[8]{} ^^J
-          \providecommand\chemnum@subcmpd[4]{} ^^J
-          \providecommand\chemnum@check{}
-        }
-    \fi
+    \legacy_if:nT {@filesw}
+      {
+        \iow_now:Nn \@auxout
+          {
+            \providecommand\chemnum@cmpd[8]{} ^^J
+            \providecommand\chemnum@subcmpd[4]{} ^^J
+            \providecommand\chemnum@check{}
+          }
+      }
   }
 
 % we use this one to trigger a LaTeX rerun warning -- to be precise the
@@ -528,7 +541,11 @@
   { \AtEndDocument { \def \chemnum@check { \@tempswatrue } } }
 
 % add the rerun check at the end:
-\AtEndDocument { \if@filesw \iow_now:Nn \@auxout { \chemnum@check } \fi }
+\AtEndDocument
+  {
+    \legacy_if:nT {@filesw}
+      { \iow_now:Nn \@auxout { \chemnum@check } }
+  }
 
 % ----------------------------------------------------------------------------
 % initiating new compounds
@@ -624,8 +641,8 @@
         \int_gincr:N \g__chemnum_main_int
         \stepcounter{cmpdmain}
       }
-    \seq_if_exist:cF { g__chemnum_#1_initiated_subcompounds_seq }
-      { \seq_new:c { g__chemnum_#1_initiated_subcompounds_seq } }
+    \seq_if_exist:cF {g__chemnum_#1_initiated_subcompounds_seq}
+      { \seq_new:c {g__chemnum_#1_initiated_subcompounds_seq} }
   }
 
 % #1: main ID
@@ -643,11 +660,11 @@
     \chemnum_subcompound_set_property:nnnn {#1} {#2} {ID} {#2}
     \chemnum_subcompound_set_property:nnnn {#1} {#2} {main-compound} {#1}
     \chemnum_subcompound_set_property:nnnx {#1} {#2} {number}
-      { \int_use:c { g__chemnum_compound_#1_subcompound_int } }
+      { \int_use:c {g__chemnum_compound_#1_subcompound_int} }
     \chemnum_subcompound_set_property:nnnx {#1} {#2} {counter-representation}
       {
         \__chemnum_label_format:cV
-          { g__chemnum_compound_#1_subcompound_int }
+          {g__chemnum_compound_#1_subcompound_int}
           \l__chemnum_default_subcounter_representation_tl
       }
   }
@@ -661,26 +678,41 @@
 
 \cs_new_protected:Npn \chemnum_initialize_subcompound:nn #1#2
   {
-    \int_if_exist:cF { g__chemnum_compound_#1_subcompound_int }
-      { \int_new:c { g__chemnum_compound_#1_subcompound_int } }
-    \int_gincr:c { g__chemnum_compound_#1_subcompound_int }
-    \seq_if_exist:cF { g__chemnum_compound_#1_subcompounds_seq }
-      { \seq_new:c { g__chemnum_compound_#1_subcompounds_seq } }
-    \prop_if_exist:cF { g__chemnum_compound_#1_subcompounds_prop }
-      { \prop_new:c { g__chemnum_compound_#1_subcompounds_prop } }
-    \seq_if_in:cnF { g__chemnum_compound_#1_subcompounds_seq } {#2}
-      { \seq_gput_right:cn { g__chemnum_compound_#1_subcompounds_seq } {#2} }
+    \int_if_exist:cF {g__chemnum_compound_#1_subcompound_int}
+      { \int_new:c {g__chemnum_compound_#1_subcompound_int} }
+    \int_gincr:c {g__chemnum_compound_#1_subcompound_int}
+    \seq_if_exist:cF {g__chemnum_compound_#1_subcompounds_seq}
+      { \seq_new:c {g__chemnum_compound_#1_subcompounds_seq} }
+    \prop_if_exist:cF {g__chemnum_compound_#1_subcompounds_prop}
+      { \prop_new:c {g__chemnum_compound_#1_subcompounds_prop} }
+    \seq_if_in:cnF {g__chemnum_compound_#1_subcompounds_seq} {#2}
+      { \seq_gput_right:cn {g__chemnum_compound_#1_subcompounds_seq} {#2} }
     \seq_gput_right:Nn \g__chemnum_compound_defined_subcompounds_seq {#1#2}
-    \prop_gput:cnx { g__chemnum_compound_#1_subcompounds_prop } {#2}
+    \prop_gput:cnx {g__chemnum_compound_#1_subcompounds_prop} {#2}
       {
-        \int_use:c { g__chemnum_compound_#1_subcompound_int } :
+        \int_use:c {g__chemnum_compound_#1_subcompound_int} :
         \__chemnum_label_format:cV
-          { g__chemnum_compound_#1_subcompound_int }
+          {g__chemnum_compound_#1_subcompound_int}
           \l__chemnum_default_subcounter_representation_tl
       }
   }
 
 % ----------------------------------------------------------------------------
+
+\cs_new:Npn \__chemnum_nothing_here:n #1
+  {
+    \c_chemnum_nothing_here_tl
+    \msg_warning:nnn {chemnum} {missing-label} {#1}
+  }
+
+\cs_new:Npn \__chemnum_nothing_here:nn #1#2
+  {
+    \c_chemnum_nothing_here_tl
+    \msg_warning:nnnn {chemnum} {missing-label} {#1} {#2}
+  }
+\cs_generate_variant:Nn \__chemnum_nothing_here:nn {x}
+  
+% ----------------------------------------------------------------------------
 \cs_new_protected:Npn \chemnum_log_main:n #1
   {
     \bool_if:NT \l__chemnum_log_bool
@@ -716,7 +748,7 @@
 \prg_new_protected_conditional:Npnn \chemnum_subcompound_if_initiated:nn #1#2
   { T,F,TF }
   {
-    \seq_if_in:cnTF { g__chemnum_#1_initiated_subcompounds_seq } {#2}
+    \seq_if_in:cnTF {g__chemnum_#1_initiated_subcompounds_seq} {#2}
       { \prg_return_true: }
       { \prg_return_false: }
   }
@@ -745,12 +777,12 @@
 % #2: property to be defined
 \cs_new_protected:Npn \chemnum_compound_declare_property:nn #1#2
   {
-    \seq_if_exist:cF { g__chemnum_compound_#1_properties_seq }
-      { \seq_new:c { g__chemnum_compound_#1_properties_seq } }
-    \prop_if_exist:cF { g__chemnum_compound_#1_prop }
-      { \prop_new:c { g__chemnum_compound_#1_prop } }
-    \seq_if_in:cnF { g__chemnum_compound_#1_properties_seq } {#2}
-      { \seq_gput_right:cn { g__chemnum_compound_#1_properties_seq } {#2} }
+    \seq_if_exist:cF {g__chemnum_compound_#1_properties_seq }
+      { \seq_new:c {g__chemnum_compound_#1_properties_seq} }
+    \prop_if_exist:cF {g__chemnum_compound_#1_prop}
+      { \prop_new:c {g__chemnum_compound_#1_prop} }
+    \seq_if_in:cnF {g__chemnum_compound_#1_properties_seq} {#2}
+      { \seq_gput_right:cn {g__chemnum_compound_#1_properties_seq} {#2} }
   }
 
 % #1: ID
@@ -766,8 +798,8 @@
 % #3: value of property
 \cs_new_protected:Npn \chemnum_compound_set_property:nnn #1#2#3
   {
-    \seq_if_in:cnTF { g__chemnum_compound_#1_properties_seq } {#2}
-      { \prop_gput:cnn { g__chemnum_compound_#1_prop } {#2} {#3} }
+    \seq_if_in:cnTF {g__chemnum_compound_#1_properties_seq} {#2}
+      { \prop_gput:cnn {g__chemnum_compound_#1_prop} {#2} {#3} }
       { \msg_error:nnn {chemnum} {property-undefined} {#1} {#2} }
   }
 \cs_generate_variant:Nn \chemnum_compound_set_property:nnn { nnV , nnx }
@@ -776,15 +808,15 @@
 % #2: property to be updated
 \cs_new_protected:Npn \chemnum_compound_update_property:nn #1#2
   {
-    \seq_if_in:cnTF { g__chemnum_compound_#1_properties_seq } {#2}
+    \seq_if_in:cnTF {g__chemnum_compound_#1_properties_seq} {#2}
       {
-        \prop_get:cnN { g__chemnum_compound_#1_prop } {previous-#2}
+        \prop_get:cnN {g__chemnum_compound_#1_prop} {previous-#2}
           \l__chemnum_tmpa_tl
-        \prop_get:cnN { g__chemnum_compound_#1_prop } {#2}
+        \prop_get:cnN {g__chemnum_compound_#1_prop} {#2}
           \l__chemnum_tmpb_tl
         \tl_if_eq:NNF \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
           {
-            \prop_gput:cnV { g__chemnum_compound_#1_prop }
+            \prop_gput:cnV {g__chemnum_compound_#1_prop}
               {previous-#2}
               \l__chemnum_tmpb_tl
           }
@@ -795,7 +827,7 @@
 % #1: ID
 \cs_new_protected:Npn \chemnum_compound_update_properties:n #1
   {
-    \seq_map_inline:cn { g__chemnum_compound_#1_properties_seq }
+    \seq_map_inline:cn {g__chemnum_compound_#1_properties_seq}
       { \chemnum_compound_update_property:nn {#1} {##1} }
   }
 
@@ -804,8 +836,8 @@
 % #3: property to be defined
 \cs_new_protected:Npn \chemnum_subcompound_declare_property:nnn #1#2#3
   {
-    \seq_if_in:cnF { g__chemnum_compound_#1_#2_properties_seq } {#3}
-      { \seq_gput_right:cn { g__chemnum_compound_#1_#2_properties_seq } {#3} }
+    \seq_if_in:cnF {g__chemnum_compound_#1_#2_properties_seq} {#3}
+      { \seq_gput_right:cn {g__chemnum_compound_#1_#2_properties_seq} {#3} }
   }
 
 % #1: main ID
@@ -813,11 +845,11 @@
 % #3: properties to be defined
 \cs_new_protected:Npn \chemnum_subcompound_declare_properties:nnn #1#2#3
   {
-    \seq_if_exist:cF { g__chemnum_compound_#1_#2_properties_seq }
-      { \seq_new:c { g__chemnum_compound_#1_#2_properties_seq } }
-    \prop_if_exist:cF { g__chemnum_compound_#1_#2_properties_prop }
-      { \prop_new:c { g__chemnum_compound_#1_#2_properties_prop } }
-    \clist_map_inline:nn { #3 }
+    \seq_if_exist:cF {g__chemnum_compound_#1_#2_properties_seq}
+      { \seq_new:c {g__chemnum_compound_#1_#2_properties_seq} }
+    \prop_if_exist:cF {g__chemnum_compound_#1_#2_properties_prop}
+      { \prop_new:c {g__chemnum_compound_#1_#2_properties_prop} }
+    \clist_map_inline:nn {#3}
       { \chemnum_subcompound_declare_property:nnn {#1} {#2} {##1} }
   }
 
@@ -827,8 +859,8 @@
 % #4: value of property
 \cs_new_protected:Npn \chemnum_subcompound_set_property:nnnn #1#2#3#4
   {
-    \seq_if_in:cnTF { g__chemnum_compound_#1_#2_properties_seq } {#3}
-      { \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop } {#3} {#4} }
+    \seq_if_in:cnTF {g__chemnum_compound_#1_#2_properties_seq} {#3}
+      { \prop_gput:cnn {g__chemnum_compound_#1_#2_properties_prop} {#3} {#4} }
       { \msg_error:nnn {chemnum} {property-undefined} {#1.#2} {#3} }
   }
 \cs_generate_variant:Nn \chemnum_subcompound_set_property:nnnn { nnnV , nnnx }
@@ -838,15 +870,15 @@
 % #3: property to be updated
 \cs_new_protected:Npn \chemnum_subcompound_update_property:nnn #1#2#3
   {
-    \seq_if_in:cnTF { g__chemnum_compound_#1_#2_properties_seq }
+    \seq_if_in:cnTF {g__chemnum_compound_#1_#2_properties_seq}
       {
-        \prop_get:cnN { g__chemnum_compound_#1_#2_properties_prop } {previous-#3}
+        \prop_get:cnN {g__chemnum_compound_#1_#2_properties_prop} {previous-#3}
           \l__chemnum_tmpa_tl
-        \prop_get:cnN { g__chemnum_compound_#1_#2_properties_prop } {#3}
+        \prop_get:cnN {g__chemnum_compound_#1_#2_properties_prop} {#3}
           \l__chemnum_tmpb_tl
         \tl_if_eq:NNF \l__chemnum_tmpb_tl \l__chemnum_tmpa_tl
           {
-            \prop_gput:cnV { g__chemnum_compound_#1_#2_properties_prop }
+            \prop_gput:cnV {g__chemnum_compound_#1_#2_properties_prop}
               {previous-#3}
               \l__chemnum_tmpb_tl
           }
@@ -858,7 +890,7 @@
 % #2: sub ID
 \cs_new_protected:Npn \chemnum_subcompound_update_properties:nn #1#2
   {
-    \seq_map_inline:cn { g__chemnum_compound_#1_#2_properties_seq }
+    \seq_map_inline:cn {g__chemnum_compound_#1_#2_properties_seq}
       { \chemnum_subcompound_update_property:nnn {#1} {#2} {##1} }
   }
 
@@ -869,14 +901,14 @@
 
 \cs_new_protected:Npn \chemnum_get_compound_property_or:nnn #1#2#3
   {
-    \prop_get:cnNTF { g__chemnum_compound_#1_prop } {#2}
+    \prop_get:cnNTF {g__chemnum_compound_#1_prop} {#2}
       \l__chemnum_tmpa_tl
       { \tl_use:N \l__chemnum_tmpa_tl }
       {#3}
   }
 
 \cs_new:Npn \chemnum_expandable_get_compound_property:nn #1#2
-  { \prop_item:cn { g__chemnum_compound_#1_prop } {#2} }
+  { \prop_item:cn {g__chemnum_compound_#1_prop} {#2} }
 \cs_generate_variant:Nn \chemnum_expandable_get_compound_property:nn { V }
 
 % #1: main ID
@@ -887,14 +919,14 @@
 
 \cs_new_protected:Npn \chemnum_get_subcompound_property_or:nnnn #1#2#3#4
   {
-    \prop_get:cnNTF { g__chemnum_compound_#1_#2_properties_prop } {#3}
+    \prop_get:cnNTF {g__chemnum_compound_#1_#2_properties_prop} {#3}
       \l__chemnum_tmpa_tl
       { \tl_use:N \l__chemnum_tmpa_tl }
       {#4}
   }
 
 \cs_new:Npn \chemnum_expandable_get_subcompound_property:nnn #1#2#3
-  { \prop_item:cn { g__chemnum_compound_#1_#2_properties_prop } {#3} }
+  { \prop_item:cn {g__chemnum_compound_#1_#2_properties_prop} {#3} }
 
 % ----------------------------------------------------------------------------
 \DeclareExpandableDocumentCommand \cmpdproperty { mm }
@@ -911,7 +943,7 @@
 \cs_new_protected:Npn \chemnum_initiate_subcompound:nn #1#2
   {
     \chemnum_subcompound_if_initiated:nnF {#1} {#2}
-      { \seq_gput_right:cn { g__chemnum_#1_initiated_subcompounds_seq } {#2} }
+      { \seq_gput_right:cn {g__chemnum_#1_initiated_subcompounds_seq} {#2} }
   }
 
 % ----------------------------------------------------------------------------
@@ -927,13 +959,11 @@
 % #8: label format
 \cs_new_protected:Npn \__chemnum_write_compound_to_auxfile_x:nnnnnnnn #1#2#3#4#5#6#7#8
   {
-    \if@filesw
-      \token_if_eq_meaning:NNT \@nodocument \relax
-        {
-          \iow_now:Nx \@auxout
-            { \exp_not:N \chemnum@cmpd {#1}{#2}{#3}{#4}{#5}{#6}{#7}{#8} }
-        }
-    \fi
+    \legacy_if:nT {@filesw}
+      {
+        \iow_now:Nx \@auxout
+          { \exp_not:N \chemnum@cmpd {#1}{#2}{#3}{#4}{#5}{#6}{#7}{#8} }
+      }
   }
 \cs_generate_variant:Nn \__chemnum_write_compound_to_auxfile_x:nnnnnnnn { nnnVVVVV }
 
@@ -955,13 +985,11 @@
 % #3: counter representation
 \cs_new_protected:Npn \__chemnum_write_subcompound_to_auxfile_x:nnnn #1#2#3#4
   {
-    \if@filesw
-      \token_if_eq_meaning:NNT \@nodocument \relax
-        {
-          \iow_now:Nx \@auxout
-            { \exp_not:N \chemnum@subcmpd {#1}{#2}{#3}{#4} }
-        }
-    \fi
+    \legacy_if:nT {@filesw}
+      {
+        \iow_now:Nx \@auxout
+          { \exp_not:N \chemnum@subcmpd {#1}{#2}{#3}{#4} }
+      }
   }
 
 \cs_new_protected:Npn \chemnum_save_subcompound_to_auxfile:nn #1#2
@@ -989,21 +1017,21 @@
 \cs_new_protected:Npn \chemnum@cmpd #1#2#3#4#5#6#7#8
   {
     % \chemnum_initialize_compound:n {#1} 
-    \prop_if_exist:cF { g__chemnum_compound_#1_prop }
-      { \prop_new:c { g__chemnum_compound_#1_prop } }
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_if_exist:cF {g__chemnum_compound_#1_prop}
+      { \prop_new:c {g__chemnum_compound_#1_prop} }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-number} {#2}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-counter-representation} {#3}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-pre-label-code} {#4}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-post-label-code} {#5}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-pre-main-label-code} {#6}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-post-main-label-code} {#7}
-    \prop_gput:cnn { g__chemnum_compound_#1_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_prop}
       {previous-label-format} {#8}
   }
 
@@ -1013,15 +1041,15 @@
 % #4: counter representation
 \cs_new_protected:Npn \chemnum@subcmpd #1#2#3#4
   {
-    \prop_if_exist:cF { g__chemnum_compound_#1_#2_properties_prop }
-      { \prop_new:c { g__chemnum_compound_#1_#2_properties_prop } }
-    \seq_if_exist:cF { g__chemnum_compound_#1_subcompounds_seq }
-      { \seq_new:c { g__chemnum_compound_#1_subcompounds_seq } }
-    \seq_if_in:cnF { g__chemnum_compound_#1_subcompounds_seq } {#2}
-      { \seq_gput_right:cn { g__chemnum_compound_#1_subcompounds_seq } {#2} }
-    \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop }
+    \prop_if_exist:cF {g__chemnum_compound_#1_#2_properties_prop}
+      { \prop_new:c {g__chemnum_compound_#1_#2_properties_prop} }
+    \seq_if_exist:cF {g__chemnum_compound_#1_subcompounds_seq}
+      { \seq_new:c {g__chemnum_compound_#1_subcompounds_seq} }
+    \seq_if_in:cnF {g__chemnum_compound_#1_subcompounds_seq} {#2}
+      { \seq_gput_right:cn {g__chemnum_compound_#1_subcompounds_seq} {#2} }
+    \prop_gput:cnn {g__chemnum_compound_#1_#2_properties_prop}
       {previous-number} {#3}
-    \prop_gput:cnn { g__chemnum_compound_#1_#2_properties_prop }
+    \prop_gput:cnn {g__chemnum_compound_#1_#2_properties_prop}
       {previous-counter-representation} {#4}
   }
 
@@ -1060,7 +1088,6 @@
 % #3: sub ID
 \cs_new_protected:Npn \chemnum_declare_subcompound:nnn #1#2#3
   {
-    % \keys_set:nn {chemnum} {#1}
     \chemnum_subcompound_if_initiated:nnF {#2} {#3}
       {
         \bool_if:NT \g__chemnum_initiate_sub_bool
@@ -1170,8 +1197,11 @@
       \chemnum_get_compound_property:nn {#1} {previous-label-format}
       {
         \chemnum_get_compound_property_or:nnn {#1}
-          { previous-counter-representation }
-          { ?? \__chemnum_rerun: }
+          {previous-counter-representation}
+          {
+            \__chemnum_nothing_here:n {#1}
+            \__chemnum_rerun:
+          }
       }
     \group_end:
     \chemnum_get_compound_property:nn {#1} {previous-post-main-label-code}
@@ -1189,7 +1219,10 @@
       {
         \chemnum_get_subcompound_property_or:nnnn {#1} {#2}
           {previous-counter-representation}
-          { ?? \__chemnum_rerun: }
+          {
+            \__chemnum_nothing_here:nn {#2} {#1}
+            \__chemnum_rerun:
+          }
       }
     \group_end:
   }
@@ -1265,7 +1298,7 @@
           {
             \tl_clear:N \l__chemnum_tmpa_tl
             \tl_set:Nx \l__chemnum_tmpa_tl
-              { \seq_use:cn { g__chemnum_compound_##4_subcompounds_seq } { , } }
+              { \seq_use:cn {g__chemnum_compound_##4_subcompounds_seq} {,} }
             \tl_if_blank:VF \l__chemnum_tmpa_tl
               {
                 \chemnum_write_sublist:NNnnV ##1 ##2 {##3} {##4}
@@ -1294,8 +1327,8 @@
   {
     \bool_if:NTF #2
       {
-        \chemnum_hyper_link:nn {#4}
-          { \chemnum_compound_read:n {#4} }
+        \bool_if:NF \l__chemnum_sub_only_bool
+          { \chemnum_hyper_link:nn {#4} { \chemnum_compound_read:n {#4} } }
         \bool_if:NT #1
           { \msg_error:nn {chemnum} {erroneous-argument-combination} }
       }
@@ -1353,10 +1386,18 @@
   }
 
 % ----------------------------------------------------------------------------
-\cs_set_protected:Npn \chemnum_show_key_def:n #1
-  { \marginpar { \fbox { \normalfont \ttfamily #1 } } }
+\cs_new_protected:Npn \chemnum_print_label_id:n #1
+  {
+    \group_begin:
+      \str_set:Nn \l__chemnum_tmpa_str {#1}
+      \str_use:N \l__chemnum_tmpa_str
+    \group_end:
+  }
+
+\cs_new_protected:Npn \chemnum_show_label_margin:n #1
+  { \marginpar { \fbox {#1} } }
 
-\cs_set_protected:Npn \chemnum_show_key_ref:n #1
+\cs_new_protected:Npn \chemnum_show_label_inline:n #1
   {
     \group_begin:
       \hbox_unpack:N \c_empty_box % this is \leavevmode
@@ -1366,18 +1407,38 @@
           \hbox_overlap_right:n
             {
               \tex_vrule:D \tex_raise:D .75em
-              \hbox:n
-                { \underbar { \normalfont \footnotesize \ttfamily #1 } }
+              \hbox:n { \underbar {#1} }
             }
         }
     \group_end:
   }
 
-% ----------------------------------------------------------------------------
+\NewDocumentCommand \cmpdprintlabelid {m}
+  { \chemnum_print_label_id:n {#1} }
+
+\NewDocumentCommand \cmpdshowlabelmargin {m}
+  { \chemnum_show_label_margin:n {#1} }
+  
+\NewDocumentCommand \cmpdshowlabelinline {m}
+  { \chemnum_show_label_inline:n {#1} }
+
 \NewDocumentCommand \chemnumshowdef {m}
-  { \chemnum_show_key_def:n {#1} }
+  {
+    \cmpdshowlabelmargin
+      {
+        \normalfont \ttfamily
+        \cmpdprintlabelid {#1}
+      }
+  }
+  
 \NewDocumentCommand \chemnumshowref {m}
-  { \chemnum_show_key_ref:n {#1} }
+  {
+    \cmpdshowlabelinline
+      {
+        \normalfont \ttfamily \footnotesize
+        \cmpdprintlabelid {#1}
+      }
+  }
 
 \NewDocumentCommand \cmpdshowdef {m} { \chemnumshowdef {#1} }
 \NewDocumentCommand \cmpdshowref {m} { \chemnumshowref {#1} }
@@ -1396,7 +1457,7 @@
       \l__chemnum_tmpc_seq
       \l__chemnum_sub_separator_tl
       {#5}
-    \seq_remove_duplicates:N \l__chemnum_tmpc_seq
+    \seq_remove_duplicates:N \l__chemnum_tmpc_seq  
     \seq_map_inline:Nn \l__chemnum_tmpc_seq
       {
         \bool_if:NF #2
@@ -1467,29 +1528,34 @@
     \seq_clear:N #7
     \bool_if:NF #1
       {
-        \seq_map_inline:cn { g__chemnum_compound_#5_subcompounds_seq }
+        \seq_if_exist:cTF {g__chemnum_compound_#5_subcompounds_seq}
           {
-            \seq_if_in:NnT #3 {##1}
+            \seq_map_inline:Nn #3
               {
-                \seq_put_right:Nn #6
-                  { \chemnum_write_subcompound:NNnnn #1 #2 {#4} {#5} {##1} }
-                \bool_if:NTF #2
+                \seq_if_in:cnTF {g__chemnum_compound_#5_subcompounds_seq} {##1}
                   {
-                    \seq_put_right:Nx #7
+                    \seq_put_right:Nn #6
+                      { \chemnum_write_subcompound:NNnnn #1 #2 {#4} {#5} {##1} }
+                    \bool_if:NTF #2
                       {
-                        \chemnum_expandable_get_subcompound_property:nnn
-                          {#5} {##1} {previous-number}
+                        \seq_put_right:Nx #7
+                          {
+                            \chemnum_expandable_get_subcompound_property:nnn
+                              {#5} {##1} {previous-number}
+                          }
                       }
-                  }
-                  {
-                    \seq_put_right:Nx #7
                       {
-                        \chemnum_expandable_get_subcompound_property:nnn
-                          {#5} {##1} {number}
+                        \seq_put_right:Nx #7
+                          {
+                            \chemnum_expandable_get_subcompound_property:nnn
+                              {#5} {##1} {number}
+                          }
                       }
                   }
+                  { \__chemnum_nothing_here:nn {##1} {#5} }
               }
           }
+          { \__chemnum_nothing_here:xn { \seq_use:Nnnn #3 {,~} {,~} {,~} } {#5} }
       }
   }
 
@@ -1917,8 +1983,8 @@
   }
 
 \NewDocumentCommand \initcmpd {O{}m}
-  { \chemnum_init:nn {#1} {#2} }
-\@onlypreamble\cmpdinit
+  { \AtBeginDocument { \chemnum_init:nn {#1} {#2} } }
+\@onlypreamble\initcmpd
 
 % ----------------------------------------------------------------------------
 % resetting compound numbering
@@ -2008,4 +2074,10 @@ HISTORY:
                    \prop_item:Nn)
 2016/04/14 v1.2  - changes to how compounds are saved to auxfile
                  - hyperref support: backlinks to first appearance of label
-
+2016/05/11 v1.2a - pre- and post-label options now belong both to the
+                   `compound' and the `general' groups
+2016/10/22 v1.2b - enable label keys to be printed (with `show-keys') if they
+                   contain underscores or similar tokens
+                 - easier customization possibilities of the `show-keys'
+                   functions
+2019/10/02 v1.2c - fix issues #5, #7