xsim number chapterwise in own exercise environment

Question

My code is:

\documentclass{scrbook}
\usepackage[utf8]{inputenc}
%Rahmenumgebung
\usepackage{tcolorbox}
\usepackage[ngerman]{babel}
\tcbuselibrary{skins,breakable,xparse}
\usepackage[%
    blank,%With this option enabled xsim will not dene the default environments exercise 
]{xsim}
\DeclareExerciseProperty{level}
\DeclareExerciseProperty{symbole}
\DeclareExerciseProperty{notenstufe}
\DeclareExerciseEnvironmentTemplate{aufgabe-template}{%
    \tcolorbox[
      parbox=false,
      enhanced jigsaw,
      breakable,%auskommentieren, wenn die Aufgaben in einer einzigen Box zusammenhängen sollen
      left=1mm,%Abstand links zum Rahmen
      right=1mm,%Abstand rechts zum Rahmen
      colframe=blue!30!white,%Rahmenfarbe
      colback=white,%Hintergrundfarbe
      %colbacktitle=white,%Hintergrundfarbe im Titel
      coltitle=white,%Schriftfarbe im Titel
      beforeafter skip = .5\baselineskip,
      title ={
        \textbf{\GetExerciseName~\GetExerciseProperty{section}.\GetExerciseProperty{counter}}%Aufgabe mit Nummer ausgeben
        \GetExercisePropertyT{level}{ Level:\PropertyValue}%evtl. Level mit Knödeln anzeigen
        \GetExercisePropertyT{symbole}{ \PropertyValue}%evtl. Symbole anzeigen
        \GetExercisePropertyT{notenstufe}{ (N:\PropertyValue)}%evtl. Symbole anzeigen
        \IfInsideSolutionF{%Wenn nicht(F=False) in der Lösung
            \GetExercisePropertyT{points}{ % notice the space
                (%
                \printgoal{\PropertyValue}
                \IfExerciseGoalSingularTF{points}
                    {\XSIMtranslate{point}}
                    {\XSIMtranslate{points}}%
                )%
            }%
        }%
        \GetExercisePropertyT{subtitle}{\\PropertyValue}%evtl Subtitle in neuer Zeile (\) ausgeben
      },
      pad at break*=0mm,%sollte immer letzte Option sein, weil diverse Anpassungen dadurch ausgelöst werden.
    ]
    %nachfolgender Befehl wird nicht gebraucht, wenn mit parbox=false oben gearbeitet wird.
    %\setlength{\parskip}{0.5\baselineskip plus2pt minus2pt}%
}
{\endtcolorbox}
\DeclareExerciseType{Aufgabe}{
    exercise-env = n-Aufgabe,
    solution-env = n-Solution,
    exercise-name = Aufgabe,
    exercises-name = Aufgaben,
    solution-name = Lösung von Aufgabe,
    solutions-name = Lösungen,
    exercise-template = aufgabe-template,
    solution-template = aufgabe-template,
    counter=counter-aufgabe,
    within=section,
    the-counter = \thesection.\arabic{counter-aufgabe}
}
\begin{document}
\chapter{Chapter 1}
\section{Section 1.1}
%====================================================================
\begin{n-Aufgabe}[%
    level=1,%
    %symbole=,%
    subtitle={Subtitle 1},%
    notenstufe=2,%
    points=1,%
]
Exercise Text 1
\end{n-Aufgabe}
\begin{n-Solution}
Solution Text 1
\end{n-Solution}
\begin{n-Aufgabe}[%
    level=1,%
    %symbole=,%
    subtitle={Subtitle 2},%
    notenstufe=2,%
    points=2,%
]
Exercise Text 2
\end{n-Aufgabe}
\begin{n-Solution}
Solution Text 2
\end{n-Solution}
\section{Section 1.2}
%==========================================================================
\begin{n-Aufgabe}[%
    level=3,%
    %symbole=,%
    subtitle={Subtitle 3},%
    notenstufe=4,%
    points=20,%
]
Exercise Text 3
\end{n-Aufgabe}
\begin{n-Solution}
Solution Text 3
\end{n-Solution}
\begin{n-Aufgabe}[%
    level=2,%
    %symbole=,%
    subtitle={Subtitle 4},%
    notenstufe=1,%
    %points=,%
]
Exercise Text 4
\end{n-Aufgabe}
\begin{n-Solution}
Solution Text 4
\end{n-Solution}
\end{document}

The goal is that the counter for the exercises (in German: Aufgabe) starts anew in each section:

1 Chapter 1

1.1 Section 1.1

Aufgabe 1.1.1

Aufgabe 1.1.2

1.2 Section 1.2

Aufgabe 1.2.1

Aufgabe 1.2.2

Whats the best way to do this?

The usage of

counter = counter-aufgabe,
within = section,
the-counter = \ thesection. \ arabic {counter-aufgabe}

is not really clear for me. I miss a working example to this. Most the examples I found for sectionwise numbering are based on the standard xsim environments. I had to switch off the standard environments (option: "blank" for xsim see above) because I have already defined an environment with the name "exercise" myself and the name for the environment is therefore no longer free.

Answer 1

I'm always amazed how things wander around in the internet. I have never seen the code before yet I recognize one of my own comments there (% notice the space) maybe copy-pasted from xsim.style.layouts.code.tex file (or not, it's % <<< notice the space there) or from one of my answers until it found its way to you.

---

My original answer was wrong and I've deleted it.

---

You cannot set within and the-counter as parameters in \DeclareExerciseType. Unfortunately undefined parameters are simply ignored by that command. The next version will throw an error in these cases.

Both within and the-counter only exist as options and can be set with \xsimsetup:

\documentclass{book}
\usepackage[blank]{xsim}
\DeclareExerciseType{Aufgabe}{
  exercise-env = n-Aufgabe,
  solution-env = n-Solution,
  exercise-name = Aufgabe,
  solution-name = Lösung von Aufgabe,
  exercise-template = default ,
  solution-template = default ,
  counter=counter-aufgabe
}
\xsimsetup{
  n-Aufgabe/within=section ,
  n-Aufgabe/the-counter = \thesection.\arabic{counter-aufgabe}
}
\begin{document}
\chapter{Chapter 1}
\section{Section 1.1}
\begin{n-Aufgabe}
  Exercise Text 1
\end{n-Aufgabe}
\begin{n-Aufgabe}
  Exercise Text 2
\end{n-Aufgabe}
\section{Section 1.2}
\begin{n-Aufgabe}
  Exercise Text 3
\end{n-Aufgabe}
\begin{n-Aufgabe}
  Exercise Text 4
\end{n-Aufgabe}
\end{document}