[gesposito]

What / why

context.name of a private member is only its description, like "#value". The 2022.3 @observable and @computed decorators use it as the key in the administration, so two separate private members that happen to have the same name, one on a class and one on its subclass, end up under one key:

class Parent {
    @observable accessor #value = 1
    get parentValue() {
        return this.#value
    }
}

class Child extends Parent {
    @observable accessor #value = 2
    get childValue() {
        return this.#value
    }
}

const child = new Child()
child.parentValue // 2, expected 1

A write to the parent's field changes the subclass's field as well. A private @observable accessor on the parent and a private @computed getter with the same name on the subclass collide the same way: the parent's field returns the computed value.

Private members now get a key of their own, a symbol that carries the name as its description. Public members keep context.name. Debug names are unchanged (Store@1.#value).

Behavior change

A private member could not be addressed reliably by its name before, because the name is not unique per object. Now it cannot be addressed by name at all: isObservableProp(obj, "#value"), getAtom(obj, "#value") and observe(obj, "#value", ...) no longer find it, and the change events of a private field that object-level observe and spy receive carry the symbol as name. toJS already left private fields out.

Tests

• Three tests in stage3-decorators-inheritance.ts. The accessor/accessor and accessor/computed cases fail on main. The computed/computed case already passed, because the override handling from fix(mobx): create overridden @computed eagerly so super reads get the parent value #4756 covers it, and now guards the new key.
• One assertion in the New decorators and enumerability #4248 toJS test looked up the internal lazy map by "#secret" and is updated to the new key.
• Full mobx suite passes (805 tests).

Code change checklist

• Added/updated unit tests
• Updated /docs: no documented behavior changes
• Verified that there is no significant performance drop (npm -w mobx run test:performance): only the key of private members changes, the read and write paths are the same

[changeset-bot]

🦋 Changeset detected

Latest commit: d1ddc46

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 1 package

Name	Type
mobx	Patch

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