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Backport Option.orElse from effect/ #1868

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May 22, 2023
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Backport Option.orElse from effect/ #1868

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22 changes: 22 additions & 0 deletions src/Option.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -901,6 +901,28 @@ export const getOrElseW =
*/
export const getOrElse: <A>(onNone: LazyArg<A>) => (ma: Option<A>) => A = getOrElseW

/**
* Returns the provided `Option` `that` if `self` is `None`, otherwise returns `self`.
*
* @param self - The first `Option` to be checked.
* @param that - The `Option` to return if `self` is `None`.
*
* @example
* import * as O from "fp-ts/Option"
*
* assert.deepStrictEqual(O.orElse(O.none, () => O.none), O.none)
* assert.deepStrictEqual(O.orElse(O.some(1), () => O.none), O.some(1))
* assert.deepStrictEqual(O.orElse(O.none, () => O.some('b')), O.some('b'))
* assert.deepStrictEqual(O.orElse(O.some(1), () => O.some('b')), O.some(1))
*
* @category error handling
* @since 2.16.0
*/
export const orElse: {
<B>(that: LazyArg<Option<B>>): <A>(self: Option<A>) => Option<A | B>
<A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B>
} = dual(2, <A, B>(self: Option<A>, that: LazyArg<Option<B>>): Option<A | B> => (isNone(self) ? that() : self))

/**
* @category mapping
* @since 2.10.0
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