Deprecate Selector's compute_default_fn slot and compute_default() method

[maximlt]

As suggested in #508 (comment).

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 87.26%. Comparing base (8095bb3) to head (9f32e5e).

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1012      +/-   ##
==========================================
+ Coverage   87.25%   87.26%   +0.01%     
==========================================
  Files           9        9              
  Lines        4928     4932       +4     
==========================================
+ Hits         4300     4304       +4     
  Misses        628      628              

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[maximlt]

@philippjfr @jbednar do you agree with this deprecation?

[jbednar]

I agree with this deprecation (and in fact I think I suggested it a while back :-) ). I see you've removed documentation of the old way to do it, so I assume that the new way to do it has already been documented appropriately in a separate PR?

[maximlt]

I agree with this deprecation (and in fact I think I suggested it a while back :-) ). I see you've removed documentation of the old way to do it, so I assume that the new way to do it has already been documented appropriately in a separate PR?

I'm working separately on default_factory but haven't opened a PR yet (you will know about it!). The main motivation for deprecating compute_default_fn/compute_defaut() is that it is imo a weird API and it appears to be unused (see more details in #508 (comment), with only 3 occurrences found on Github in topographica). As such I don't see a need to document how to reproduce what this feature was achieving. For the users who might need this feature, they can easily reproduce it as the code is trivial:

    def compute_default(self):
        """
        If this parameter's compute_default_fn is callable, call it
        and store the result in self.default.

        Also removes None from the list of objects (if the default is
        no longer None).
        """
        if self.default is None and callable(self.compute_default_fn):
            self.default = self.compute_default_fn()
            self._ensure_value_is_in_objects(self.default)

    def _ensure_value_is_in_objects(self, val):
        """
        Make sure that the provided value is present on the objects list.
        Subclasses can override if they support multiple items on a list,
        to check each item instead.
        """
        if val not in self.objects:
            self._objects.append(val)