Mobx-state-tree: applyPatch will not replace root of store

[skokenes]

• [x] I've checked documentation and searched for existing issues
• [x] I tried the spectrum channel

Is there anyway to use applyPatch to update a snapshot in the same way you might do an applySnapshot? With JSON patching, I'd expect to be able to replace a store using a patch like:
{
op: "replace",
path: "",
value: {} // new store snapshot
}
However, patches like this never work for me in MST. See this example code showing it in action with a simple model:
https://codesandbox.io/embed/lively-shape-lmjgo

[mweststrate]

It is not possible to replace a thing itself, as that would require all
javascript pointer that point to that object to be updated, which is
impossible. Either create patches that replace all fields of the root
object, or wrap another object around the root so that there is an entry
point.

On Mon, Oct 28, 2019 at 2:57 PM Speros Kokenes [e-mail]
wrote:

>

• I've checked documentation and searched for existing issues
• I tried the spectrum channel
  https://spectrum.chat/?t=dad48299-3dfc-4e10-b6da-9af1e39498a3

Is there anyway to use applyPatch to update a snapshot in the same way you
might do an applySnapshot? With JSON patching, I'd expect to be able to
replace a store using a patch like:
{
op: "replace",
path: "",
value: {} // new store snapshot
}
However, patches like this never work for me in MST. See this example code
showing it in action with a simple model:
https://codesandbox.io/embed/lively-shape-lmjgo

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[mweststrate]

A Test + PR that will make MST error on such cases is welcome (condition: node is root, path is empty), or alternative, a fix that automatically "unpacks" the value to apply it to the individual fields

[skokenes]

I see. How does that differ from applying a snapshot? Don't they
conceptually do the same thing? Ie, replace the entire structure

On Mon, Oct 28, 2019, 7:53 PM Michel Weststrate [e-mail]
wrote:

A Test + PR that will make MST error on such cases is welcome (condition:
node is root, path is empty)

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[mweststrate]

Yeah, thinking longer about, I think it is a bug and it should behave is
one would expect :)

On Mon, Oct 28, 2019 at 6:58 PM Speros Kokenes [e-mail]
wrote:

I see. How does that differ from applying a snapshot? Don't they
conceptually do the same thing? Ie, replace the entire structure

On Mon, Oct 28, 2019, 7:53 PM Michel Weststrate [e-mail]
wrote:

A Test + PR that will make MST error on such cases is welcome (condition:
node is root, path is empty)

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[Bnaya]

I don't know if its directly related but,
I have a WTF feeling earlier this year when after using MST for a while,
this code didn't work on sub property and not the root

   const MyModel = types.model("MyModel", {
      arr1: types.array(types.string)
    });

    const model = MyModel.create({
      arr1: ["c"]
    });

    unprotect(model);

    const fn = jest.fn();
    reaction(() => model.arr1, fn);

    // not passing also with that
    // applySnapshot(model.arr1, ["a", "b"]);
    // @ts-ignore
    model.arr1 = ["a", "b"];

Full example:
https://codesandbox.io/s/mobx-state-tree-arrays-wtf-zonww?fontsize=14&previewwindow=tests

[epodgaetskiy]

@Bnaya You can use toJS https://codesandbox.io/s/mobx-state-tree-arrays-wtf-pji90