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Dec 27, 2022
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immer-reducers.md better rule for state mutations #3038

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immer-reducers.md better rule for state mutations
Luk-z Dec 27, 2022
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Fix formatting
markerikson Dec 27, 2022
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16 changes: 12 additions & 4 deletions docs/usage/immer-reducers.md
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Expand Up @@ -453,13 +453,21 @@ const itemsSlice = createSlice({

Many ESLint configs include the https://eslint.org/docs/rules/no-param-reassign rule, which may also warn about mutations to nested fields. That can cause the rule to warn about mutations to `state` in Immer-powered reducers, which is not helpful.

To resolve this, you can tell the ESLint rule to ignore mutations to a parameter named `state`:
To resolve this, you can tell the ESLint rule to ignore mutations and assignment to a parameter named `state` only in slice files:

```js
{
'no-param-reassign': ['error', { props: true, ignorePropertyModificationsFor: ['state'] }]
// @filename .eslintrc.js
module.exports = {
// add to your ESLint config definition
overrides: [
{
// feel free to replace with your preferred file pattern - eg. 'src/**/*Slice.ts'
files: ['src/**/*.slice.ts'],
// avoid state param assignment
rules: { 'no-param-reassign': ['error', { props: false }] },
},
],
}

```

## Why Immer is Built In
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