# optional - !xx doesn't work

[user202729]

Assume you have a doc test of the form

sage: 2 # optional - !xx

and run sage -t --optional=xx a.py, the doc test is still run.

The problem is there are multiple places that populate the list…

First in doctest/control

                # We replace the 'optional' tag by all optional
                # packages for which the installed version matches the
                # latest available version (this implies in particular
                # that the package is actually installed).
                if 'optional' in options.optional:
                    options.optional.discard('optional')
                    from sage.misc.package import list_packages
                    for pkg in list_packages('optional', local=True).values():
                        if pkg.name in options.hide:
                            continue
                        # Skip features for which we have a more specific runtime feature test.
                        if pkg.name in ['bliss', 'coxeter3', 'mcqd', 'meataxe', 'sirocco', 'tdlib']:
                            continue
                        if pkg.is_installed() and pkg.installed_version == pkg.remote_version:
                            options.optional.add(pkg.name)

Second in doctest/parsing

                        for tag in optional_tags:
                            if tag not in self.optional_tags:
                                if tag.startswith('!'):
                                    if tag[1:] in available_software:
                                        extra.add(tag)
                                elif tag not in available_software:
                                    extra.add(tag)

In this case the xx is put in options.optional by the first block, then it goes to self.optional_tags, which triggers the check, but tag[1:] in available_software returns False. Here extra is the list of "extra conditions" for the doctest to be run.