34 lines
848 B
Plaintext
34 lines
848 B
Plaintext
import type {IsEqual} from './is-equal';
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/**
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Extract all writable keys from the given type.
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This is useful when you want to create a new type that contains writable keys only.
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@example
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```
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import type {WritableKeysOf} from 'type-fest';
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interface User {
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name: string;
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surname: string;
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readonly id: number;
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}
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type UpdateRequest<Entity extends object> = Pick<Entity, WritableKeysOf<Entity>>;
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const update1: UpdateRequest<User> = {
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name: 'Alice',
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surname: 'Acme',
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};
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```
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@category Utilities
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*/
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export type WritableKeysOf<T> =
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T extends unknown // For distributing `T`
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? (keyof {
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[P in keyof T as IsEqual<{[Q in P]: T[P]}, {readonly [Q in P]: T[P]}> extends false ? P : never]: never
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}) & keyof T // Intersect with `keyof T` to ensure result of `WritableKeysOf<T>` is always assignable to `keyof T`
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: never; // Should never happen
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