How I can I set a default question point value in the exam class?

Question

I'm writing an exam in the exam class and I'd like to set the point value for an entire group of questions at once. For example:

\documentclass{exam}
\title{Know your US States and Capitals!}


\begin{document}

\begin{questions}

\begingroup
\defaultpoints{2}
\question What is the capital of California?
\begin{choices}
    \choice Los Angeles
    \choice Sacramento
    \choice San Francisco
    \choice San Diego
\end{choices}

\question Which city serves as the capital of Texas?
\begin{choices}
    \choice Dallas
    \choice Houston
    \choice Austin
    \choice San Antonio
\end{choices}

\question What is the capital of Florida?
\begin{choices}
    \choice Miami
    \choice Orlando
    \choice Jacksonville
    \choice Tallahassee
\end{choices}

\endgroup

\begingroup
\defaultpoints{3}
\question Which city is the capital of New York?
\begin{choices}
    \choice Buffalo
    \choice Albany
    \choice New York City
    \choice Syracuse
\end{choices}

\question What is the capital of Nevada?
\begin{choices}
    \choice Reno
    \choice Henderson
    \choice Carson City
    \choice Las Vegas
\end{choices}

\question Which city serves as the capital of Colorado?
\begin{choices}
    \choice Denver
    \choice Boulder
    \choice Colorado Springs
    \choice Aurora
\end{choices}

\question What is the capital of Massachusetts?
\begin{choices}
    \choice Springfield
    \choice Boston
    \choice Worcester
    \choice Cambridge
\end{choices}

\question Which city is the capital of Washington state?
\begin{choices}
    \choice Seattle
    \choice Tacoma
    \choice Spokane
    \choice Olympia
\end{choices}
\endgroup

% no points should be specified
\question What is the capital of Hawaii?
\begin{choices}
    \choice Maui
    \choice Honolulu
    \choice Kauai
    \choice Hilo
\end{choices}

\question[5] Which city serves as the capital of Ohio?
\begin{choices}
    \choice Cincinnati
    \choice Columbus
    \choice Cleveland
    \choice Dayton
\end{choices}

\end{questions}    
\end{document}

(N.B. I don't mean to comment on the actual difficulty of these questions!)

The output should be the same as if the first three questions were declared with \question[2], and the next five with \question[3]. The ninth question is outside a group of default points, so shouldn't have any points attached to it. The last question should work as a normal question with points defined.

I have a h@cky solution already and I will post it eventually, but I'm curious to see if there are better ones.

Answer 1

Basically just redefine \question to call \oldQuestion[⟨default value⟩].

Note the use of \DeclareCommandCopy (declare = if already defined, do nothing) in order to not override the definition of \oldQuestion in case the default point is already set once in a group.

This assumes all commands are defined locally in a group (which seems to be quite safe because the LaTeX maintainers really don't want to break backwards compatibility).

%! TEX program = pdflatex
\documentclass{exam}
\title{Know your US States and Capitals!}

\NewDocumentCommand\defaultpoints{m}{%
  \DeclareCommandCopy\oldQuestion\question%
  \RenewDocumentCommand\question{O{#1}}{%
    \oldQuestion[##1]%
  }%
}

\begin{document}

\begin{questions}

\begingroup
\defaultpoints{2}
\question What is the capital of California?
\begin{choices}
    \choice Los Angeles
    \choice Sacramento
    \choice San Francisco
    \choice San Diego
\end{choices}

\question Which city serves as the capital of Texas?
\begin{choices}
    \choice Dallas
    \choice Houston
    \choice Austin
    \choice San Antonio
\end{choices}

\question What is the capital of Florida?
\begin{choices}
    \choice Miami
    \choice Orlando
    \choice Jacksonville
    \choice Tallahassee
\end{choices}

\endgroup

\begingroup
\defaultpoints{3}
\question Which city is the capital of New York?
\begin{choices}
    \choice Buffalo
    \choice Albany
    \choice New York City
    \choice Syracuse
\end{choices}

\question What is the capital of Nevada?
\begin{choices}
    \choice Reno
    \choice Henderson
    \choice Carson City
    \choice Las Vegas
\end{choices}

\question Which city serves as the capital of Colorado?
\begin{choices}
    \choice Denver
    \choice Boulder
    \choice Colorado Springs
    \choice Aurora
\end{choices}

\question What is the capital of Massachusetts?
\begin{choices}
    \choice Springfield
    \choice Boston
    \choice Worcester
    \choice Cambridge
\end{choices}

\question Which city is the capital of Washington state?
\begin{choices}
    \choice Seattle
    \choice Tacoma
    \choice Spokane
    \choice Olympia
\end{choices}
\endgroup

% no points should be specified
\question What is the capital of Hawaii?
\begin{choices}
    \choice Maui
    \choice Honolulu
    \choice Kauai
    \choice Hilo
\end{choices}

\question[5] Which city serves as the capital of Ohio?
\begin{choices}
    \choice Cincinnati
    \choice Columbus
    \choice Cleveland
    \choice Dayton
\end{choices}

\end{questions}    
\end{document}

Answer 2

Here is the solution I came up with originally. In the preamble:

\makeatletter
\let\orig@doitem\@doitem
\newcommand{\defaultpoints}[1]{
   \def\@doitem{\@ifnextchar[{\@readpoints}{\@readpoints[#1]}}
}
\newcommand{\nodefaultpoints}{
    \let\@doitem\orig@doitem
}
\makeatother

As you can see, my LaTeX habits are old. I duplicated \@doitem for safekeeping and redefined \@doitem to call \@readpoints on the default point number in the absence of any declared number.

But this relies on the internals of the \question command. The solution by user202729 is cleaner and simpler.