64 lines
1.5 KiB
Plaintext
64 lines
1.5 KiB
Plaintext
---
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description: 'Disallow the declaration of empty interfaces.'
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---
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import Tabs from '@theme/Tabs';
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import TabItem from '@theme/TabItem';
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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-empty-interface** for documentation.
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An empty interface in TypeScript does very little: any non-nullable value is assignable to `{}`.
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Using an empty interface is often a sign of programmer error, such as misunderstanding the concept of `{}` or forgetting to fill in fields.
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This rule aims to ensure that only meaningful interfaces are declared in the code.
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## Examples
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<Tabs>
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<TabItem value="❌ Incorrect">
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```ts
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// an empty interface
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interface Foo {}
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// an interface with only one supertype (Bar === Foo)
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interface Bar extends Foo {}
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// an interface with an empty list of supertypes
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interface Baz {}
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```
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</TabItem>
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<TabItem value="✅ Correct">
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```ts
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// an interface with any number of members
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interface Foo {
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name: string;
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}
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// same as above
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interface Bar {
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age: number;
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}
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// an interface with more than one supertype
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// in this case the interface can be used as a replacement of an intersection type.
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interface Baz extends Foo, Bar {}
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```
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</TabItem>
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</Tabs>
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## Options
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### `allowSingleExtends`
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`allowSingleExtends: true` will silence warnings about extending a single interface without adding additional members
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## When Not To Use It
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If you don't care about having empty/meaningless interfaces, then you will not need this rule.
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