compare original state with reference equality

[jackielii]

I have a reducer created using createSlice. Inside one of the case reducer, I'd like to compare with the original state with reference equality. How do I achieve this?

const slice = createSlice({
  name: 'filter',
  initialState: emptyConstraint,
  reducers: {
    addPlain(state, action: PayloadAction<{ parent: Constraint.AsObject }>) {
      if (state === action.payload.parent) { // <<<< how should I do equality check? do I need to import: https://immerjs.github.io/immer/docs/original
          // do something with state
      }
    },
})

[phryneas]

You can use original from immer:

import {original] from 'immer';

if (original(state) === action.payload.parent)

[jackielii]

You can use original from immer:

This is what I end up doing, however, I had to add immer as an explicit dependency as it's not re-exported. Would this be ok? Will there be any incompatibilities?

[jackielii]

@phryneas turns out it doesn't always work.

If I just do yarn add immer, it installs 8.0.0. original calls isDraft which will return false because the draft from redux-toolkit is different from immer

Did found a workaround: In Yarn, I have to align the immer version to exactly redux-toolkit is using so that yarn resolves them to the same immer source code inside node_modules.

However, the workaround is flaky and since redux-toolkit re-exports some of the immer's functions like current, I think we should export original as well.

[phryneas]

The current RTK 1.5 uses immer 8.0.0. But yeah, probably we should re-export original as it is quite useful. Actually, I thought we already did that. @markerikson what are your thoughts? We had good uses for original in performance scenarios if I recall correctly

[markerikson]

Probably reasonable to re-export that too, yeah.