I ran into an issue where I had the code:

@click.option( "--print-verbose-info/--print-verbose-info", help="...", default=False )

...and running cli.py --print-verbose-info was apparently defaulting over to the False value. Totally my mistake (it should have been --no-print-verbose-info), but it'd be nice to get a warning/error for boolean values which match exactly (ie: cannot be set to true).

It was kindof tricky to diagnose b/c I assumed that the --print-verbose-info that I was passing on the CLI was triggering the True path, not the False path, and usually Click option parsing is pretty bulletproof so it took a while to find that copy/paste problem.

This would be a good-first-issue, I'm submitting it now more as a reminder to maybe follow-up on it and figure out the appropriate P.R.