63 lines
1.6 KiB
Plaintext
63 lines
1.6 KiB
Plaintext
---
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description: 'Disallow non-null assertion in locations that may be confusing.'
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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-confusing-non-null-assertion** for documentation.
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Using a non-null assertion (`!`) next to an assign or equals check (`=` or `==` or `===`) creates code that is confusing as it looks similar to a not equals check (`!=` `!==`).
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```typescript
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a! == b; // a non-null assertions(`!`) and an equals test(`==`)
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a !== b; // not equals test(`!==`)
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a! === b; // a non-null assertions(`!`) and an triple equals test(`===`)
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```
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This rule flags confusing `!` assertions and suggests either removing them or wrapping the asserted expression in `()` parenthesis.
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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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interface Foo {
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bar?: string;
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num?: number;
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}
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const foo: Foo = getFoo();
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const isEqualsBar = foo.bar! == 'hello';
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const isEqualsNum = 1 + foo.num! == 2;
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```
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</TabItem>
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<TabItem value="✅ Correct">
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{/* prettier-ignore */}
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```ts
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interface Foo {
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bar?: string;
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num?: number;
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}
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const foo: Foo = getFoo();
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const isEqualsBar = foo.bar == 'hello';
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const isEqualsNum = (1 + foo.num!) == 2;
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```
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</TabItem>
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</Tabs>
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## When Not To Use It
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If you don't care about this confusion, then you will not need this rule.
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## Further Reading
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- [`Issue: Easy misunderstanding: "! ==="`](https://github.com/microsoft/TypeScript/issues/37837) in [TypeScript repo](https://github.com/microsoft/TypeScript)
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