Label numbering gone crazy

Question

I have redefined the enumerate counters to include the section number, and this works as expected. However, when I try to cross-reference text in my document, the number on the reference doesn't show correctly.

Update:
Upon request, I have edited in a full MWE here instead of the original sample code.

\documentclass{article}

\renewcommand*{\theenumi}{\thesection.\arabic{enumi}}
\renewcommand*{\theenumii}{\theenumi.\arabic{enumii}}
\renewcommand*{\theenumiii}{\theenumii.\arabic{enumiii}}

\begin{document}

\section{The main stuff}
\begin{enumerate}
    \item Some text
    \item \textbf{A header}
    \begin{enumerate}
        \item The first item in a sublist
        \item \label{important} This stuff is really cool
        \begin{enumerate}
            \item Some text here...
            \item ...and here
        \end{enumerate}
    \end{enumerate}
    \item The outer list continues
\end{enumerate}

When I reference \lq\lq{}important\rq\rq{}, I get \ref{important}

\end{document}

The last row outputs

When I reference "important", I get 1.21.2.2

where I would have expected the number to be just simply 1.2.2.

Solution:
The solution to this problem was presented by Geoffrey Jones - simply switching from one suggested way of changing the numbering to the other made it work. Instead of the above \newcommands, the following works:

\usepackage{enumitem}
\setenumerate[1]{label=\thesection.\arabic*.}
\setenumerate[2]{label*=\arabic*.}
\setenumerate[3]{label*=\arabic*.}

Answer 1

Tomas, I've tried my best to replicate your problem but no matter what I do, I can't get anything to go wrong at all. In the absence of your providing a MWE (which, frankly, I wish you could have supplied), I'm guessing that your code looks essentially like this:

\documentclass{article}
\usepackage{verbatim}     % this is just for the print-out below
\usepackage{enumitem}     % for lack of a MWE, I'm just guessing here
\setenumerate[1]{label=\thesection.\arabic*.}
\setenumerate[2]{label*=\arabic*.}
\setenumerate[3]{label*=\arabic*.}

\begin{document}
\setcounter{section}{3}   % to remain in sync with your numbering
\section{The main stuff}
  \begin{enumerate}
    \item Some text
    \item \textbf{A header}
    \begin{enumerate}     % NB, your code had \begin{item} here which, judging by 
                          % your printout, I assume to be another typo (correct me
                          % if I'm wrong
      \item The first item in a sublist
      \item \label{important} This stuff is really cool
      \begin{enumerate}   % NB, ditto
          \item Some text here...
          \item ...and here
      \end{enumerate}
    \end{enumerate}
  \end{enumerate}
  ``When I reference this label (\verb|\ref{important}|), 
  the number that shows up is \ref{important}''
\end{document}

Apart from the listing part of my printout coinciding with your listing in your question, my code includes the following line:

"When I reference this label (\ref{important}), the number that shows up is 4.2.2."

So obviously our code does not coincide. Can you help me out by providing a MWE that doesn't leaving people guessing about what's causing the problem you see?

Answer 2

Tomas, excellent update. Now we can see what's going on.

As odd as the result you see is at first glance, it happens that your odd output is exactly what LaTeX should produce without further modifications from you. Here's a modified version of your (new) code to help you see what's going on (sorry for the long lines):

\documentclass{article}
\usepackage{verbatim}
\usepackage[margin=1in]{geometry}

%\renewcommand*{\theenumi}{\thesection.\arabic{enumi}}  % run once without uncommenting, review output, then uncomment and run again
%\renewcommand*{\theenumii}{\theenumi.\arabic{enumii}}  % uncomment after running and reviewing ouput from uncommented line above

\begin{document}
\section{Stuff}
  \begin{enumerate}
    \item This line contains \verb|\label{a}|. \label{a} \verb|\labelenumi|: \labelenumi;\ \verb|\theenumi|: \theenumi
    \item This line contains \verb|\label{b}|. \label{b} \verb|\labelenumi|: \labelenumi;\ \verb|\theenumi|: \theenumi
    \begin{enumerate}
      \item This line contains \verb|\label{c}|. \label{c} \verb|\labelenumii|: \labelenumii;\ \verb|\theenumii|: \theenumii
      \item This line contains \verb|\label{d}|. \label{d} \verb|\labelenumii|: \labelenumii;\ \verb|\theenumii|: \theenumii
      \begin{enumerate}
        \item This line contains \verb|\label{e}|. \label{e} \verb|\labelenumiii|: \labelenumiii;\ \verb|\theenumiii|: \theenumiii
        \item This line contains \verb|\label{f}|. \label{f} \verb|\labelenumiii|: \labelenumiii;\ \verb|\theenumiii|: \theenumiii
      \end{enumerate}
    \end{enumerate}
  \end{enumerate}
  \verb|\ref|'s to \verb|\label|'s\{a, b, c, d, e, f\}: \ref{a}, \ref{b}, \ref{c}, \ref{d}, \ref{e}, \ref{f}.
\end{document}

As you can see if you run this code as is, the output LaTeX produces is:

\ref's to \label's{a, b, c, d, e, f}: 1, 2, 2a, 2b, 2(b)i, 2(b)ii.

I hope you'll agree that that is the result everyone would ordinarily expect LaTeX to produce.

Now, if you uncomment the first of your \renewcommand's, your output will include:

\ref's to \label's{a, b, c, d, e, f}: 1.1, 1.2, 1.2a, 1.2b, 1.2(b)i, 1.2(b)ii.

OK, so now it's starting to look a little strange. But it follows from what we just saw before (right?).

Finally, if you uncomment the second of your \renewcommand's, you'll see:

\ref's to \label's{a, b, c, d, e, f}: 1.1, 1.2, 1.21.2.1, 1.21.2.2, 1.2(1.2.2)i, 1.2(1.2.2)ii.

which, while exactly as you describe in your problem statement, nevertheless follows consistently from the results we saw in our previous tests above.

So now you can see what's going on (and that your expectations about the output you saw didn't account for the way LaTeX prints labels in enumerate environments).

To fix this (which I wouldn't bother with given the working solution I provided above), you're going to need to dive into redefining LaTeX's \p@enumii and \p@enumiii, but that's a whole new kettle of fish.