Feb 19, 2024 · Feb 19, 2024 · Feb 19, 2024 · Feb 19, 2024 · Feb 20, 2024 · Feb 20, 2024
diff --git a/packages/eslint-plugin/docs/rules/no-misused-spread.mdx b/packages/eslint-plugin/docs/rules/no-misused-spread.mdx
 ---
 description: 'Disallow using the spread operator when it might cause unexpected behavior.'
 ---

 import Tabs from '@theme/Tabs';
 import TabItem from '@theme/TabItem';

 > 🛑 This file is source code, not the primary documentation location! 🛑
 >
 > See **https://typescript-eslint.io/rules/no-misused-spread** for documentation.

 The [spread operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax) (`...`) is a JavaScript
 feature that can be misused in ways not always reported by TypeScript. This rule disallows using the spread operator on types where
 spreading can lead to unexpected behavior.

 This rule disallows the spread operator in the following cases:

 - Spreading a string into an array
 - Spreading a `Promise` into an object
 - Spreading a function without properties into an object
 - Spreading a class instance or declaration into an object
 - Spreading an iterable (`Map`, `Array`, etc.) into an object

 ## Examples

 <Tabs>
 <TabItem value="❌ Incorrect">

 ```ts
 declare const userName: string;
 const chars = [...userName];

 declare const arr: number[];
 const arrSpread = { ...arr };

 declare const set: Set<number>;
 const setSpread = { ...set };

 declare const map: Map<string, number>;
 const mapSpread = { ...map };

 declare function getObj(): { a: 1; b: 2 };
 const getObjSpread = { ...getObj };
 ```

 </TabItem>
 <TabItem value="✅ Correct">

 ```ts
 declare const userName: string;
 const chars = userName.split('');

 declare const arr: number[];
 const arrSpread = [...arr];

 declare const set: Set<number>;
 const setSpread = [...set];

 declare const map: Map<string, number>;
 const mapObject = Object.fromEntries(map);

 declare function getObj(): { a: 1; b: 2 };
 const getObjSpread = { ...getObj() };
 ```

 </TabItem>
 </Tabs>

 ## Options

 ### `allow`

 This option allows marking specific types as "safe" to be spread. It takes an
 array of type specifiers to consider safe.

 This option takes the shared [`TypeOrValueSpecifier` format](/packages/type-utils/type-or-value-specifier).

 Examples of a configuration for this option:

 ```json
 "@typescript-eslint/no-misused-spread": [
  "error",
  {
    "allowForKnownSafeIterables": [
      "SafeType",
      { "from": "file", "name": "SafeString", "path": "src/safe-string.ts" },
      { "from": "lib", "name": "BrandedArray" },
      { "from": "package", "name": "ThisIsSafe", "package": "safe-lib" }
    ]
  }
 ]
 ```

 <Tabs>
 <TabItem value="❌ Incorrect">

 ```ts
 type UnsafeIterable = Iterable<number>;

 declare const iterable: UnsafeIterable;

 const spreadIterable = { ...iterable };

 type UnsafeBrandedString = string & { __brand: 'unsafe' };

 declare const brandedString: UnsafeBrandedString;

 const spreadBrandedString = { ...brandedString };
 ```

 </TabItem>
 <TabItem value="✅ Correct">

 ```ts option='{"allow":["SafeIterable", "BrandedString"]}'
 type SafeIterable = Iterable<number>;

 declare const iterable: SafeIterable;

 const spreadIterable = { ...iterable };

 type BrandedString = string & { __brand: 'safe' };

 declare const brandedString: BrandedString;

 const spreadBrandedString = { ...brandedString };
 ```

 </TabItem>
 </Tabs>

 ## When Not To Use It

 If you intentionally want to use the spread operator in those cases, and expect
 the specific behavior that comes with it, you might not want this rule.
 For example, when you want to spread an array into an object and expect the
 result to be an object with the array elements as values and the array indices
 as keys.

 If your use cases for unusual spreads only involve a few types, you might consider using
 [ESLint disable comments](https://eslint.org/docs/latest/use/configure/rules#using-configuration-comments-1)
 and/or the [`allow` option](#allow) instead of completely disabling this rule.
diff --git a/packages/eslint-plugin/src/configs/all.ts b/packages/eslint-plugin/src/configs/all.ts
    '@typescript-eslint/no-meaningless-void-operator': 'error',
    '@typescript-eslint/no-misused-new': 'error',
    '@typescript-eslint/no-misused-promises': 'error',
    '@typescript-eslint/no-misused-spread': 'error',
    '@typescript-eslint/no-mixed-enums': 'error',
    '@typescript-eslint/no-namespace': 'error',
    '@typescript-eslint/no-non-null-asserted-nullish-coalescing': 'error',
diff --git a/packages/eslint-plugin/src/configs/disable-type-checked.ts b/packages/eslint-plugin/src/configs/disable-type-checked.ts
    '@typescript-eslint/no-implied-eval': 'off',
    '@typescript-eslint/no-meaningless-void-operator': 'off',
    '@typescript-eslint/no-misused-promises': 'off',
    '@typescript-eslint/no-misused-spread': 'off',
    '@typescript-eslint/no-mixed-enums': 'off',
    '@typescript-eslint/no-redundant-type-constituents': 'off',
    '@typescript-eslint/no-unnecessary-boolean-literal-compare': 'off',
diff --git a/packages/eslint-plugin/src/configs/strict-type-checked-only.ts b/packages/eslint-plugin/src/configs/strict-type-checked-only.ts
    '@typescript-eslint/no-implied-eval': 'error',
    '@typescript-eslint/no-meaningless-void-operator': 'error',
    '@typescript-eslint/no-misused-promises': 'error',
    '@typescript-eslint/no-misused-spread': 'error',
    '@typescript-eslint/no-mixed-enums': 'error',
    '@typescript-eslint/no-redundant-type-constituents': 'error',
    '@typescript-eslint/no-unnecessary-boolean-literal-compare': 'error',
diff --git a/packages/eslint-plugin/src/configs/strict-type-checked.ts b/packages/eslint-plugin/src/configs/strict-type-checked.ts
    '@typescript-eslint/no-meaningless-void-operator': 'error',
    '@typescript-eslint/no-misused-new': 'error',
    '@typescript-eslint/no-misused-promises': 'error',
    '@typescript-eslint/no-misused-spread': 'error',
    '@typescript-eslint/no-mixed-enums': 'error',
    '@typescript-eslint/no-namespace': 'error',
    '@typescript-eslint/no-non-null-asserted-nullish-coalescing': 'error',
diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
 import noMeaninglessVoidOperator from './no-meaningless-void-operator';
 import noMisusedNew from './no-misused-new';
 import noMisusedPromises from './no-misused-promises';
 import noMisusedSpread from './no-misused-spread';
 import noMixedEnums from './no-mixed-enums';
 import noNamespace from './no-namespace';
 import noNonNullAssertedNullishCoalescing from './no-non-null-asserted-nullish-coalescing';
  'no-meaningless-void-operator': noMeaninglessVoidOperator,
  'no-misused-new': noMisusedNew,
  'no-misused-promises': noMisusedPromises,
  'no-misused-spread': noMisusedSpread,
  'no-mixed-enums': noMixedEnums,
  'no-namespace': noNamespace,
  'no-non-null-asserted-nullish-coalescing': noNonNullAssertedNullishCoalescing,
Original file line number	Diff line number	Diff line change
		@@ -0,0 +1,141 @@
		---
		description: 'Disallow using the spread operator when it might cause unexpected behavior.'
		---

		import Tabs from '@theme/Tabs';
		import TabItem from '@theme/TabItem';

		> 🛑 This file is source code, not the primary documentation location! 🛑
		>
		> See https://typescript-eslint.io/rules/no-misused-spread for documentation.

		The [spread operator](https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Operators/Spread_syntax) (`...`) is a JavaScript
JoshuaKGoldberg marked this conversation as resolved. Show resolvedHide resolved
		feature that can be misused in ways not always reported by TypeScript. This rule disallows using the spread operator on types where
		spreading can lead to unexpected behavior.

		This rule disallows the spread operator in the following cases:
JoshuaKGoldberg marked this conversation as resolved. Show resolvedHide resolved

		- Spreading a string into an array
JoshuaKGoldberg marked this conversation as resolved. Show resolvedHide resolved
		- Spreading a `Promise` into an object
		- Spreading a function without properties into an object
		- Spreading a class instance or declaration into an object
		- Spreading an iterable (`Map`, `Array`, etc.) into an object
JoshuaKGoldberg marked this conversation as resolved. Show resolvedHide resolved

		## Examples

		<Tabs>
		<TabItem value="❌ Incorrect">

		```ts
		declare const userName: string;
		const chars = [...userName];

		declare const arr: number[];
		const arrSpread = { ...arr };

		declare const set: Set<number>;
		const setSpread = { ...set };

		declare const map: Map<string, number>;
		const mapSpread = { ...map };

		declare function getObj(): { a: 1; b: 2 };
		const getObjSpread = { ...getObj };
		```

		</TabItem>
		<TabItem value="✅ Correct">

		```ts
		declare const userName: string;
		const chars = userName.split('');

		declare const arr: number[];
		const arrSpread = [...arr];

		declare const set: Set<number>;
		const setSpread = [...set];

		declare const map: Map<string, number>;
		const mapObject = Object.fromEntries(map);

		declare function getObj(): { a: 1; b: 2 };
		const getObjSpread = { ...getObj() };
		```

		</TabItem>
		</Tabs>

		## Options

		### `allow`

		This option allows marking specific types as "safe" to be spread. It takes an
		array of type specifiers to consider safe.

		This option takes the shared [`TypeOrValueSpecifier` format](/packages/type-utils/type-or-value-specifier).

		Examples of a configuration for this option:

		```json
		"@typescript-eslint/no-misused-spread": [
		"error",
		{
		"allowForKnownSafeIterables": [
		"SafeType",
		{ "from": "file", "name": "SafeString", "path": "src/safe-string.ts" },
		{ "from": "lib", "name": "BrandedArray" },
		{ "from": "package", "name": "ThisIsSafe", "package": "safe-lib" }
		]
		}
		]
		```

		<Tabs>
		<TabItem value="❌ Incorrect">

		```ts
		type UnsafeIterable = Iterable<number>;

		declare const iterable: UnsafeIterable;

		const spreadIterable = { ...iterable };

		type UnsafeBrandedString = string & { __brand: 'unsafe' };

		declare const brandedString: UnsafeBrandedString;

		const spreadBrandedString = { ...brandedString };
		```

		</TabItem>
		<TabItem value="✅ Correct">

		```ts option='{"allow":["SafeIterable", "BrandedString"]}'
		type SafeIterable = Iterable<number>;

		declare const iterable: SafeIterable;

		const spreadIterable = { ...iterable };

		type BrandedString = string & { __brand: 'safe' };

		declare const brandedString: BrandedString;

		const spreadBrandedString = { ...brandedString };
		```

		</TabItem>
		</Tabs>

		## When Not To Use It

		If you intentionally want to use the spread operator in those cases, and expect
		the specific behavior that comes with it, you might not want this rule.
		For example, when you want to spread an array into an object and expect the
		result to be an object with the array elements as values and the array indices
		as keys.
JoshuaKGoldberg marked this conversation as resolved. Show resolvedHide resolved

		If your use cases for unusual spreads only involve a few types, you might consider using
		[ESLint disable comments](https://eslint.org/docs/latest/use/configure/rules#using-configuration-comments-1)
		and/or the [`allow` option](#allow) instead of completely disabling this rule.
Original file line number	Diff line number	Diff line change
Expand Up		@@ -74,6 +74,7 @@ export = {
		'@typescript-eslint/no-meaningless-void-operator': 'error',
		'@typescript-eslint/no-misused-new': 'error',
		'@typescript-eslint/no-misused-promises': 'error',
		'@typescript-eslint/no-misused-spread': 'error',
		'@typescript-eslint/no-mixed-enums': 'error',
		'@typescript-eslint/no-namespace': 'error',
		'@typescript-eslint/no-non-null-asserted-nullish-coalescing': 'error',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -25,6 +25,7 @@ export = {
		'@typescript-eslint/no-implied-eval': 'off',
		'@typescript-eslint/no-meaningless-void-operator': 'off',
		'@typescript-eslint/no-misused-promises': 'off',
		'@typescript-eslint/no-misused-spread': 'off',
		'@typescript-eslint/no-mixed-enums': 'off',
		'@typescript-eslint/no-redundant-type-constituents': 'off',
		'@typescript-eslint/no-unnecessary-boolean-literal-compare': 'off',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -22,6 +22,7 @@ export = {
		'@typescript-eslint/no-implied-eval': 'error',
		'@typescript-eslint/no-meaningless-void-operator': 'error',
		'@typescript-eslint/no-misused-promises': 'error',
		'@typescript-eslint/no-misused-spread': 'error',
		'@typescript-eslint/no-mixed-enums': 'error',
		'@typescript-eslint/no-redundant-type-constituents': 'error',
		'@typescript-eslint/no-unnecessary-boolean-literal-compare': 'error',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -36,6 +36,7 @@ export = {
		'@typescript-eslint/no-meaningless-void-operator': 'error',
		'@typescript-eslint/no-misused-new': 'error',
		'@typescript-eslint/no-misused-promises': 'error',
		'@typescript-eslint/no-misused-spread': 'error',
		'@typescript-eslint/no-mixed-enums': 'error',
		'@typescript-eslint/no-namespace': 'error',
		'@typescript-eslint/no-non-null-asserted-nullish-coalescing': 'error',
Expand Down
Original file line number	Diff line number	Diff line change
Expand Up		@@ -53,6 +53,7 @@ import noMagicNumbers from './no-magic-numbers';
		import noMeaninglessVoidOperator from './no-meaningless-void-operator';
		import noMisusedNew from './no-misused-new';
		import noMisusedPromises from './no-misused-promises';
		import noMisusedSpread from './no-misused-spread';
		import noMixedEnums from './no-mixed-enums';
		import noNamespace from './no-namespace';
		import noNonNullAssertedNullishCoalescing from './no-non-null-asserted-nullish-coalescing';
Expand DownExpand Up		@@ -182,6 +183,7 @@ export default {
		'no-meaningless-void-operator': noMeaninglessVoidOperator,
		'no-misused-new': noMisusedNew,
		'no-misused-promises': noMisusedPromises,
		'no-misused-spread': noMisusedSpread,
		'no-mixed-enums': noMixedEnums,
		'no-namespace': noNamespace,
		'no-non-null-asserted-nullish-coalescing': noNonNullAssertedNullishCoalescing,
Expand Down