[composites] use typing.Sequence for children argument #436
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The Python type system considers `typing.List` to be mutable, and thus invariant on its child type. This doesn't let us pass `Behaviour` subclasses to composites through the `children` parameter, forcing the use of `composite.add_child(child)` or the use of `typing.cast`. Since the `children` list is never mutated, it's better to use `typing.Sequence` here which is covariant and therefore typechecks when a list of `Behaviour` subclasses are passed in.
sea-bass
approved these changes
Aug 31, 2024
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Seems reasonable to me. This resource was helpful as a reference: https://blog.meadsteve.dev/programming/2023/09/09/typed-python-prefer-sequence-over-list/
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The Python type system considers
typing.Listto be mutable, and thus invariant on its child type. This doesn't let us passBehavioursubclasses to composites through thechildrenparameter, forcing the use ofcomposite.add_child(child)or the use oftyping.cast. Since thechildrenlist is never mutated, it's better to usetyping.Sequencehere which is covariant and therefore typechecks when a list ofBehavioursubclasses are passed in.