[WIP] Conferral Logic For Descriptors

[rmorshea]

Summary

If a descriptor has specified that it inherits attributes, and there are descriptors of the given name in the lineage of the cls which have bequeathed one or more of those attributes, then they are conferred to that descriptor. If there are attributes that should be inherited, but that have not been bequeathed, an error will be raised.

class Grandparent(HasTraits):
    i = Int(help="something descriptive")

class Parent(Grandparent):
    # Has the same help string as Grandparent.i
    i = Int().inherit("help")

class Child(Parent):
    # raises an error because no descriptor 'i'
    # in the lineage of the class Child specified
    # that it was bequeathing its "default_value"
    i = Int().inherit("default_value")

To Do

• Testing
• Docs for TraitType methods

Possible Changes

• Instead of having the methods TraitType.inherit and TraitType.bequeath we include them as argument in TraitType.__init__. I'm not sure what looks syntactically cleaner.

[minrk]

What does bequeaths accomplish that inherits alone does not? Do we really need to specify an attribute as inheritable? Can we try a version with just inherits?

[Carreau]

Closing as state for a few years, apologies for not getting this in. I want to avoid having multiple page on stale PRs on this repository.

Labelling accordingly feel free to reopen.