Unified Exception Class - Program Options Suggestion

Unified exception class

Back to Suggestions - program options library

program_option's exceptions should be grouped under one struct. Currently, we have, e.g.:

    class validation_error : public error { ... };

Instead, it should be

    class program_options_exception : public error { ... };
    class validation_error : public program_options_exception { ... };

Then, for example, you could have:

    try {
        ...
    } catch (exception& e) {
        if (dynamic_cast<program_options_exception*>(&e))
            cout << "Usage: " << ...;
    }

to print a usage message only in the case of a program_options-generated exception.

    - People/Chuck Messenger

Actually, "error" is "boost::progam_options::error" --- i.e. it's the class from which all program options exceptions are derived. Is that already what you propose?

    - People/Vladimir Prus

Oh -- so you've got your own "error"? Yes, that satisfies what I wanted.

But, the symbol "error" doesn't seem wise. I had assumed (probably wrongly) that "error" was in the std namespace. (Maybe I was thinking of "exception"). Even so, the word "error" is much too common to be used in program_option's top level.

What happens when a user does "using namespace program_options;" (which is my typical way of using boost libs)?

You might counter that you can always specify program_options::error. But I feel the genericness of the name is problematical. What if a user doesn't qualify "error"? Symbols in a library's toplevel namespace should, I feel, be reasonably specific to the library's domain.

I suggest changing "error" to "program_options_error".

    - People/Chuck Messenger

I somehow don't like boost::program_options::program_options_error. I'm -0 on this proposal -- whatever reviewers in general will decide, will do.

   - People/Vladimir Prus