Updating property in object gives possible undefined error

[Keithcat767]

Description

If I have an object in my state and I go to update a property on it when doing a full state update in an action, it will show a type error saying the object is possibly undefined, despite it being initialized when the store is created and is not optional in the store's interface.

Steps

Example:

interface TestStore {
  test: { [key: string]: string };
  tester: number;
}

const testStore = createStore<TestStore>(
  {
    test: {
      blah: "abc",
    },
    tester: 123,
  },
  {
    name: "repo",
    immer: true,
    devtools: true,
    persist: {
      enabled: true,
    },
  },
).extendActions(({ set }) => ({
  configureTest: (value: string) => {
    set("state", (draft) => {
      draft.test.blah = value;
      draft.tester = 456;
    });
  },
}));

In this example, tester can be set just fine. But test will throw the following error: TS18048: draft. test is possibly undefined.

Note that this works as expected:

configureTest: (value: string) => {
    set("test", {
      blah: value,
    });
  },

Also, not sure if this is related, or if this isn't something I should be able to do. But I would like to be able to still use immer syntax updating a single item.

set("test", (draft) => {
        draft.blah = value;
      });

Currently, the middleware isn't working and I have to do the following:

set(
        "test",
        produce(get("test"), (draft) => {
          test.blah = value;
        }),
      );

Expectation

I would expect that when I initialize the store with an object and it is not set as optional in my interface, that it is not regarded as possibly undefined when performing updates.

I think it is due to the type of draft being a partial: DraftedObject<Partial<TestStore>>. Should it be a partial if the first argument of set it defined as "state"?