Publisher: Support dynamic/cached attribute definitions

[BigRoy]

Is your feature request related to a problem? Please describe.

I'd like to expose the primaryPool and secondaryPool to the user in the New Publisher. I thought of adding this to Collect Deadline Pools:

    @classmethod
    def get_attribute_defs(cls):

        manager = ModulesManager()
        deadline_module = manager.modules_by_name["deadline"]
        pools = deadline_module.get_deadline_pools(deadline_url)

        pools_enum = {key: key for key in pools}

        from openpype.lib import EnumDef
        return [
            EnumDef("primaryPool",
                    label="Primary Pool",
                    default=cls.primary_pool,
                    items=pools_enum),
            EnumDef("secondaryPool",
                    label="Secondary Pool",
                    default=cls.secondary_pool,
                    items=pools_enum),
        ]

However the studio and user could customize the Deadline Webservice URL and the deadline pools would be a dynamic result.

For example this logic is used in maya:

try:
    default_servers = deadline_settings["deadline_urls"]
    project_servers = (
        self._project_settings["deadline"]["deadline_servers"]
    )
    self.deadline_servers = {
        k: default_servers[k]
        for k in project_servers
        if k in default_servers
    }

    if not self.deadline_servers:
        self.deadline_servers = default_servers

except AttributeError:
    # Handle situation were we had only one url for deadline.
    # get default deadline webservice url from deadline module
    self.deadline_servers = self.deadline_module.deadline_urls

Source

Describe the solution you'd like

• Be able to delay the query of e.g. deadline_module.get_deadline_pools(deadline_url) to when it'd be needed - e.g. so that it updates the Pools list when clicking on the Enum for the first time.
• Be able to "update" the available pool list e.g. another attribute definition would be changed, like the Deadline URL

Here's some pseudocode:

    @classmethod
    def get_attribute_defs(cls):

        from openpype.lib import EnumDef
        from functools import partial
        
        url_def = EnumDef("url",
                         label="Webservice URL",
                         items=project_deadline_urls)
        
        def get_pools(_url_def):
            """Return pool list based on value of url EnumDef"""
            url = _url_def.value
            manager = ModulesManager()
            deadline_module = manager.modules_by_name["deadline"]
            pools = deadline_module.get_deadline_pools(url)
            return {key: key for key in pools}
        
        fn_get_pools = partial(get_pools, url_def)

        primary_pool_def = EnumDef("primaryPool",
                                   label="Primary Pool",
                                   default=cls.primary_pool,
                                   itemgetter=fn_get_pools)
        secondary_pool_def = EnumDef("secondaryPool",
                                     label="Secondary Pool",
                                     default=cls.secondary_pool,
                                     itemgetter=fn_get_pools)

        url_def.valueChanged.connect(primary_pool_def.updateItems)
        url_def.valueChanged.connect(secondary_pool_def.updateItems)

        return [
            url_def,
            primary_pool_def,
            secondary_pool_def
        ]

Describe alternatives you've considered

Not sure what other approaches there are for the new publisher to expose this.

Additional context

Also mentioned on discord

[cuID:OP-4827]