47 lines
1.5 KiB
Plaintext
47 lines
1.5 KiB
Plaintext
---
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description: 'Disallow non-null assertions after an optional chain expression.'
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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-non-null-asserted-optional-chain** for documentation.
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`?.` optional chain expressions provide `undefined` if an object is `null` or `undefined`.
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Using a `!` non-null assertion to assert the result of an `?.` optional chain expression is non-nullable is likely wrong.
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> Most of the time, either the object was not nullable and did not need the `?.` for its property lookup, or the `!` is incorrect and introducing a type safety hole.
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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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foo?.bar!;
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foo?.bar()!;
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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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foo?.bar;
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foo?.bar();
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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 your project's types don't yet fully describe whether certain values may be nullable, such as if you're transitioning to `strictNullChecks`, this rule might create many false reports.
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You might consider using [ESLint disable comments](https://eslint.org/docs/latest/use/configure/rules#using-configuration-comments-1) for those specific situations instead of completely disabling this rule.
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## Further Reading
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- [TypeScript 3.7 Release Notes](https://www.typescriptlang.org/docs/handbook/release-notes/typescript-3-7.html)
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- [Optional Chaining Proposal](https://github.com/tc39/proposal-optional-chaining/)
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