paul j3 added the comment: Argument Groups are not designed for nesting, and despite their names and subclassing, Mutually exclusive groups and Argument Groups are not meant to be used together (with one exception).
I agree that the error is obscure, but it occurs in a particularly fragile function in the formatter, '_format_actions_usage'. That function needs a major rewrite (that's in another bug/issue). Argument Groups serve only as a way of grouping help lines. Mutually exclusive groups test arguments during parsing, and add some markings to the usage line. So they have very different purposes. I have seen questions on Stackoverflow where people try to use Argument Groups as a way of adding some sort of subgroup to the Mutually Exclusive one, one for example that implements a 'allow any of this group' logic. There is a bug/issue asking for 'inclusive' nesting groups, but production patch of that sort is long ways off. http://bugs.python.org/issue11588 This usage line (--url URL --project Prj [--dump]) | (--mergeInput input.txt [--removeDisabled]) suggests that this what you are trying do - allow any of -u,-p,-d, but disallow one of these with -m or -r. That logic is beyond the current group testing mechanism, and beyond the usage formatting code. You'll have to do your own tests, and write a custom usage line. Mutually exclusive groups can be nested in other mutual groups, but the effect isn't what you might hope. It just forms a larger mutually exclusive group; there's no subgrouping. It is possible to nest a mutually exclusive group in an Argument group; the effect is to give the mutually exclusive group a title. ---------- nosy: +paul.j3 _______________________________________ Python tracker <rep...@bugs.python.org> <http://bugs.python.org/issue26952> _______________________________________ _______________________________________________ Python-bugs-list mailing list Unsubscribe: https://mail.python.org/mailman/options/python-bugs-list/archive%40mail-archive.com
