typescript-eslint · StyleShit · Feb 19, 2024 · Feb 19, 2024 · Feb 19, 2024 · Feb 19, 2024
diff --git a/packages/eslint-plugin/docs/rules/no-misused-spread.mdx b/packages/eslint-plugin/docs/rules/no-misused-spread.mdx
@@ -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
+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
@@ -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',

diff --git a/packages/eslint-plugin/src/configs/disable-type-checked.ts b/packages/eslint-plugin/src/configs/disable-type-checked.ts
@@ -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',

diff --git a/packages/eslint-plugin/src/configs/strict-type-checked-only.ts b/packages/eslint-plugin/src/configs/strict-type-checked-only.ts
@@ -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',

diff --git a/packages/eslint-plugin/src/configs/strict-type-checked.ts b/packages/eslint-plugin/src/configs/strict-type-checked.ts
@@ -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',

diff --git a/packages/eslint-plugin/src/rules/index.ts b/packages/eslint-plugin/src/rules/index.ts
@@ -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';
@@ -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,