39 lines
1.2 KiB
PHP
39 lines
1.2 KiB
PHP
<?php
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namespace WP_Ultimo\Dependencies\Amp;
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/**
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* Creates a promise that calls $promisor only when the result of the promise is requested (i.e. onResolve() is called
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* on the promise). $promisor can return a promise or any value. If $promisor throws an exception, the promise fails
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* with that exception. If $promisor returns a Generator, it will be run as a coroutine.
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*/
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final class LazyPromise implements Promise
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{
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/** @var callable|null */
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private $promisor;
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/** @var Promise|null */
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private $promise;
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/**
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* @param callable $promisor Function which starts an async operation, returning a Promise (or any value).
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* Generators will be run as a coroutine.
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*/
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public function __construct(callable $promisor)
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{
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$this->promisor = $promisor;
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}
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/**
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* {@inheritdoc}
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*/
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public function onResolve(callable $onResolved)
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{
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if ($this->promise === null) {
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\assert($this->promisor !== null);
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$provider = $this->promisor;
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$this->promisor = null;
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$this->promise = call($provider);
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}
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\assert($this->promise !== null);
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$this->promise->onResolve($onResolved);
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}
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}
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