76 lines
2.0 KiB
Plaintext
76 lines
2.0 KiB
Plaintext
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---
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description: 'Disallow variable redeclaration.'
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---
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> 🛑 This file is source code, not the primary documentation location! 🛑
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>
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> See **https://typescript-eslint.io/rules/no-redeclare** for documentation.
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import TypeScriptOverlap from "@site/src/components/TypeScriptOverlap";
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<TypeScriptOverlap />
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This rule extends the base [`eslint/no-redeclare`](https://eslint.org/docs/rules/no-redeclare) rule.
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It adds support for TypeScript function overloads, and declaration merging.
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## Options
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This rule adds the following options:
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```ts
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interface Options extends BaseNoRedeclareOptions {
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ignoreDeclarationMerge?: boolean;
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}
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const defaultOptions: Options = {
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...baseNoRedeclareDefaultOptions,
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ignoreDeclarationMerge: true,
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};
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```
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### `ignoreDeclarationMerge`
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When set to `true`, the rule will ignore declaration merges between the following sets:
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- interface + interface
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- namespace + namespace
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- class + interface
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- class + namespace
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- class + interface + namespace
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- function + namespace
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- enum + namespace
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Examples of **correct** code with `{ ignoreDeclarationMerge: true }`:
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```ts option='{ "ignoreDeclarationMerge": true }' showPlaygroundButton
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interface A {
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prop1: 1;
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}
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interface A {
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prop2: 2;
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}
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namespace Foo {
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export const a = 1;
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}
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namespace Foo {
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export const b = 2;
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}
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class Bar {}
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namespace Bar {}
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function Baz() {}
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namespace Baz {}
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```
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**Note:** Even with this option set to true, this rule will report if you name a type and a variable the same name. **_This is intentional_**.
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Declaring a variable and a type and a variable the same is usually an accident, and it can lead to hard-to-understand code.
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If you have a rare case where you're intentionally naming a type the same name as a variable, use a disable comment. For example:
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```ts option='{ "ignoreDeclarationMerge": true }' showPlaygroundButton
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type something = string;
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// eslint-disable-next-line @typescript-eslint/no-redeclare -- intentionally naming the variable the same as the type
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const something = 2;
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```
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