Limit recursion in GroupSpec.from_zarr

[clbarnes]

Other than cases of symlink-derived infinite recursion, there might be times where you want to get the GroupSpec for the upper levels of a zarr hierarchy without downloading and parsing every metadata document. I'd envision it something like

class GroupSpec(...)
    ...
    items: Optional[dict[str, ...]]

    @classmethod
    def from_zarr(cls, group, depth=-1):
        attrs = ...
        self = cls(attrs, dict())
        self.update_items(group, depth)
        return self

    def update_items(self, group: zarr.Group, depth=-1):
        if depth == 0:
            self.items = None
            return
       
        self.items = dict()
        for key, obj in group.items():
            if isinstance(obj, zarr.Array):
                items[key] = ArraySpec.from_zarr(obj)
           else:
               items[key] = cls.from_zarr(obj, depth - 1)
            

[d-v-b]

items: Optional[dict[str, ...]]

Does this express the semantics of nullability here?

# there definitely are no subarrays or subgroups
GroupSpec(items={})

# have not checked if there are subarrays or subgroups
GroupSpec(items=None)

[clbarnes]

Yes, that's the intention; if None, it needs populating, if empty, it's empty.

[d-v-b]

this will be addressed by #25

[d-v-b]

closed by #25