Promise::settle()   C
last analyzed

Complexity

Conditions 15
Paths 9

Size

Total Lines 52
Code Lines 31

Duplication

Lines 0
Ratio 0 %

Importance

Changes 1
Bugs 1 Features 0
Metric Value
eloc 31
c 1
b 1
f 0
dl 0
loc 52
rs 5.9166
cc 15
nc 9
nop 2

How to fix   Long Method    Complexity   

Long Method

Small methods make your code easier to understand, in particular if combined with a good name. Besides, if your method is small, finding a good name is usually much easier.

For example, if you find yourself adding comments to a method's body, this is usually a good sign to extract the commented part to a new method, and use the comment as a starting point when coming up with a good name for this new method.

Commonly applied refactorings include:

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<?php
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namespace GuzzleHttp\Promise;
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/**
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 * Promises/A+ implementation that avoids recursion when possible.
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 *
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 * @link https://promisesaplus.com/
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 */
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class Promise implements PromiseInterface
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{
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    private $state = self::PENDING;
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    private $result;
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    private $cancelFn;
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    private $waitFn;
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    private $waitList;
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    private $handlers = [];
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    /**
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     * @param callable $waitFn   Fn that when invoked resolves the promise.
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     * @param callable $cancelFn Fn that when invoked cancels the promise.
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     */
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    public function __construct(
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        callable $waitFn = null,
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        callable $cancelFn = null
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    ) {
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        $this->waitFn = $waitFn;
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        $this->cancelFn = $cancelFn;
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    }
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    public function then(
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        callable $onFulfilled = null,
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        callable $onRejected = null
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    ) {
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        if ($this->state === self::PENDING) {
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            $p = new Promise(null, [$this, 'cancel']);
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            $this->handlers[] = [$p, $onFulfilled, $onRejected];
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            $p->waitList = $this->waitList;
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            $p->waitList[] = $this;
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            return $p;
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        }
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        // Return a fulfilled promise and immediately invoke any callbacks.
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        if ($this->state === self::FULFILLED) {
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            $promise = Create::promiseFor($this->result);
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            return $onFulfilled ? $promise->then($onFulfilled) : $promise;
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        }
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        // It's either cancelled or rejected, so return a rejected promise
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        // and immediately invoke any callbacks.
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        $rejection = Create::rejectionFor($this->result);
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        return $onRejected ? $rejection->then(null, $onRejected) : $rejection;
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    }
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    public function otherwise(callable $onRejected)
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    {
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        return $this->then(null, $onRejected);
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    }
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    public function wait($unwrap = true)
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    {
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        $this->waitIfPending();
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        if ($this->result instanceof PromiseInterface) {
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            return $this->result->wait($unwrap);
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        }
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        if ($unwrap) {
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            if ($this->state === self::FULFILLED) {
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                return $this->result;
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            }
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            // It's rejected so "unwrap" and throw an exception.
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            throw Create::exceptionFor($this->result);
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        }
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    }
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    public function getState()
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    {
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        return $this->state;
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    }
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    public function cancel()
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    {
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        if ($this->state !== self::PENDING) {
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            return;
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        }
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        $this->waitFn = $this->waitList = null;
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        if ($this->cancelFn) {
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            $fn = $this->cancelFn;
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            $this->cancelFn = null;
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            try {
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                $fn();
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            } catch (\Throwable $e) {
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                $this->reject($e);
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            } catch (\Exception $e) {
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                $this->reject($e);
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            }
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        }
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        // Reject the promise only if it wasn't rejected in a then callback.
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        /** @psalm-suppress RedundantCondition */
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        if ($this->state === self::PENDING) {
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            $this->reject(new CancellationException('Promise has been cancelled'));
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        }
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    }
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    public function resolve($value)
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    {
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        $this->settle(self::FULFILLED, $value);
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    }
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    public function reject($reason)
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    {
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        $this->settle(self::REJECTED, $reason);
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    }
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    private function settle($state, $value)
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    {
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        if ($this->state !== self::PENDING) {
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            // Ignore calls with the same resolution.
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            if ($state === $this->state && $value === $this->result) {
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                return;
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            }
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            throw $this->state === $state
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                ? new \LogicException("The promise is already {$state}.")
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                : new \LogicException("Cannot change a {$this->state} promise to {$state}");
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        }
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        if ($value === $this) {
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            throw new \LogicException('Cannot fulfill or reject a promise with itself');
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        }
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        // Clear out the state of the promise but stash the handlers.
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        $this->state = $state;
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        $this->result = $value;
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        $handlers = $this->handlers;
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        $this->handlers = null;
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        $this->waitList = $this->waitFn = null;
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        $this->cancelFn = null;
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        if (!$handlers) {
0 ignored issues
show
Bug Best Practice introduced by
The expression $handlers of type array is implicitly converted to a boolean; are you sure this is intended? If so, consider using empty($expr) instead to make it clear that you intend to check for an array without elements.

This check marks implicit conversions of arrays to boolean values in a comparison. While in PHP an empty array is considered to be equal (but not identical) to false, this is not always apparent.

Consider making the comparison explicit by using empty(..) or ! empty(...) instead.

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            return;
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        }
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        // If the value was not a settled promise or a thenable, then resolve
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        // it in the task queue using the correct ID.
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        if (!is_object($value) || !method_exists($value, 'then')) {
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            $id = $state === self::FULFILLED ? 1 : 2;
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            // It's a success, so resolve the handlers in the queue.
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            Utils::queue()->add(static function () use ($id, $value, $handlers) {
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                foreach ($handlers as $handler) {
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                    self::callHandler($id, $value, $handler);
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                }
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            });
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        } elseif ($value instanceof Promise && Is::pending($value)) {
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            // We can just merge our handlers onto the next promise.
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            $value->handlers = array_merge($value->handlers, $handlers);
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        } else {
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            // Resolve the handlers when the forwarded promise is resolved.
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            $value->then(
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                static function ($value) use ($handlers) {
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                    foreach ($handlers as $handler) {
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                        self::callHandler(1, $value, $handler);
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                    }
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                },
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                static function ($reason) use ($handlers) {
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                    foreach ($handlers as $handler) {
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                        self::callHandler(2, $reason, $handler);
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                    }
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                }
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            );
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        }
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    }
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    /**
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     * Call a stack of handlers using a specific callback index and value.
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     *
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     * @param int   $index   1 (resolve) or 2 (reject).
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     * @param mixed $value   Value to pass to the callback.
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     * @param array $handler Array of handler data (promise and callbacks).
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     */
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    private static function callHandler($index, $value, array $handler)
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    {
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        /** @var PromiseInterface $promise */
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        $promise = $handler[0];
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        // The promise may have been cancelled or resolved before placing
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        // this thunk in the queue.
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        if (Is::settled($promise)) {
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            return;
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        }
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        try {
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            if (isset($handler[$index])) {
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                /*
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                 * If $f throws an exception, then $handler will be in the exception
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                 * stack trace. Since $handler contains a reference to the callable
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                 * itself we get a circular reference. We clear the $handler
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                 * here to avoid that memory leak.
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                 */
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                $f = $handler[$index];
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                unset($handler);
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                $promise->resolve($f($value));
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            } elseif ($index === 1) {
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                // Forward resolution values as-is.
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                $promise->resolve($value);
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            } else {
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                // Forward rejections down the chain.
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                $promise->reject($value);
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            }
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        } catch (\Throwable $reason) {
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            $promise->reject($reason);
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        } catch (\Exception $reason) {
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            $promise->reject($reason);
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        }
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    }
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    private function waitIfPending()
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    {
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        if ($this->state !== self::PENDING) {
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            return;
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        } elseif ($this->waitFn) {
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            $this->invokeWaitFn();
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        } elseif ($this->waitList) {
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            $this->invokeWaitList();
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        } else {
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            // If there's no wait function, then reject the promise.
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            $this->reject('Cannot wait on a promise that has '
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                . 'no internal wait function. You must provide a wait '
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                . 'function when constructing the promise to be able to '
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                . 'wait on a promise.');
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        }
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        Utils::queue()->run();
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        /** @psalm-suppress RedundantCondition */
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        if ($this->state === self::PENDING) {
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            $this->reject('Invoking the wait callback did not resolve the promise');
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        }
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    }
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    private function invokeWaitFn()
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    {
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        try {
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            $wfn = $this->waitFn;
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            $this->waitFn = null;
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            $wfn(true);
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        } catch (\Exception $reason) {
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            if ($this->state === self::PENDING) {
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                // The promise has not been resolved yet, so reject the promise
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                // with the exception.
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                $this->reject($reason);
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            } else {
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                // The promise was already resolved, so there's a problem in
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                // the application.
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                throw $reason;
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            }
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        }
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    }
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    private function invokeWaitList()
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    {
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        $waitList = $this->waitList;
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        $this->waitList = null;
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        foreach ($waitList as $result) {
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            do {
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                $result->waitIfPending();
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                $result = $result->result;
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            } while ($result instanceof Promise);
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            if ($result instanceof PromiseInterface) {
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                $result->wait(false);
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            }
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        }
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    }
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}
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