Derive :namespace only when key is present

[sitch]

Currently namespace will be overridden by any extended model regardless of whether it includes a :namespace field or not

[benjycui]

The use case?

I don't understand why do you need to share namespace with other models.

[MengWeiChen]

I think the use case is when you use umi, you don't need to write namespace in the model.

If this library override namespace whether it includes namespace field or not, the output model from this library, which namespace field will be underfined and that will cause dva crash on the runtime.

[sitch]

I expected modelExtend to be commutative in the no key collision case, and when there is a collision, it should take the last argument to define that property. This is consistent with Object.assigns()

This just seems weird/buggy/bad rationale

const { namespace } = modelExtend({}, {namespace: "users"}) 
// namespace => "users"

const { namespace } = modelExtend({namespace: "users"}, {}) 
// namespace => undefined ????? huh ???

My original use case was composing common tasks (crud / socket listeners / forms) via functions and folding them into the model.

[chapskev]

@sitch how did you manage to use umi with dva-model-extend? Will greatly appreciate your response.