Copying non-epsilon terminal nodes in parse trees using forest

Question

I'm drawing parse trees for formal grammar using the forest package and would like to have all terminals, that are not Epsilon, to be copied to the bottom and connected to the original node with a dotted line. By reading through the forest documentation I've got a somewhat working minimal example that is missing two essential things: for one, it doesn't copy the content of the original node and uses 'x' as a placeholder, and it currently isn't able to detect the Epsilon nodes and omit the copying for those.

MWE.tex:

\documentclass[paper=a4, fontsize=11pt]{scrartcl}
\usepackage{forest}

\begin{document}
\begin{forest}
    before typesetting nodes={
        where n children=0{
            append={
                [x,tier=terminal,edge=dotted]
            }
        }{}
    }
    [\(S\)
        [\(S_0\)
            [\(0\)]
            [\(S_0\)
                [\(0\)]
                [\(S_0\)
                    [\(0\)]
                    [\(S_0\)
                        [\(0\)]
                        [\(S_0\)
                            [\(0\)]
                        ]
                    [\(1\)]
                    ]
                [\(1\)]
                ]
            [\(1\)]
            ]
            [\(1\)]
        ]
        [\(S_1\)
            [\(2\)]
            [\(S_1\)
                [\(\epsilon\)]
            ]
        ]
    ]
\end{forest}
\end{document}

MWE.tex produces:

Desired result:

Answer 1

This preamble will do the trick:

before typesetting nodes={
  where n children=0{
    if content={\(\epsilon\)}{}{
      append={
        [x,tier=terminal,edge=dotted,content/.pgfmath=content("!u")]
      }
    }
  }{}
}

Answer 2

Code originally written for version 1 of forest but compiles fine with version 2.

---

Just as a supplement to Sašo Živanović's answer, note that if you use math content, you do not need to specify maths mode within every node of the tree:

\documentclass[tikz,border=10pt]{standalone}

\usepackage{forest}

\begin{document}
\begin{forest}
  before typesetting nodes={
    where n children=0{
      if content={\epsilon}{}{
        append={
          [,math content, tier=terminal, edge=dotted, content/.pgfmath=content("!u")]
        }
      }
    }{}
  },
  for tree={
    math content
  }
  [S
        [S_0
            [0]
            [S_0
                [0]
                [S_0
                    [0]
                    [S_0
                        [0]
                        [S_0
                            [0]
                        ]
                    [1]
                    ]
                [1]
                ]
            [1]
            ]
            [1]
        ]
        [S_1
            [2]
            [S_1
                [\epsilon]
            ]
        ]
    ]
\end{forest}
\end{document}