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diff --git a/bin/reevotech/vendor/guzzlehttp/promises/README.md b/bin/reevotech/vendor/guzzlehttp/promises/README.md new file mode 100644 index 00000000..7b607e28 --- /dev/null +++ b/bin/reevotech/vendor/guzzlehttp/promises/README.md @@ -0,0 +1,504 @@ +# Guzzle Promises + +[Promises/A+](https://promisesaplus.com/) implementation that handles promise +chaining and resolution iteratively, allowing for "infinite" promise chaining +while keeping the stack size constant. Read [this blog post](https://blog.domenic.me/youre-missing-the-point-of-promises/) +for a general introduction to promises. + +- [Features](#features) +- [Quick start](#quick-start) +- [Synchronous wait](#synchronous-wait) +- [Cancellation](#cancellation) +- [API](#api) + - [Promise](#promise) + - [FulfilledPromise](#fulfilledpromise) + - [RejectedPromise](#rejectedpromise) +- [Promise interop](#promise-interop) +- [Implementation notes](#implementation-notes) + + +# Features + +- [Promises/A+](https://promisesaplus.com/) implementation. +- Promise resolution and chaining is handled iteratively, allowing for + "infinite" promise chaining. +- Promises have a synchronous `wait` method. +- Promises can be cancelled. +- Works with any object that has a `then` function. +- C# style async/await coroutine promises using + `GuzzleHttp\Promise\coroutine()`. + + +# Quick start + +A *promise* represents the eventual result of an asynchronous operation. The +primary way of interacting with a promise is through its `then` method, which +registers callbacks to receive either a promise's eventual value or the reason +why the promise cannot be fulfilled. + + +## Callbacks + +Callbacks are registered with the `then` method by providing an optional +`$onFulfilled` followed by an optional `$onRejected` function. + + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise(); +$promise->then( + // $onFulfilled + function ($value) { + echo 'The promise was fulfilled.'; + }, + // $onRejected + function ($reason) { + echo 'The promise was rejected.'; + } +); +``` + +*Resolving* a promise means that you either fulfill a promise with a *value* or +reject a promise with a *reason*. Resolving a promises triggers callbacks +registered with the promises's `then` method. These callbacks are triggered +only once and in the order in which they were added. + + +## Resolving a promise + +Promises are fulfilled using the `resolve($value)` method. Resolving a promise +with any value other than a `GuzzleHttp\Promise\RejectedPromise` will trigger +all of the onFulfilled callbacks (resolving a promise with a rejected promise +will reject the promise and trigger the `$onRejected` callbacks). + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise(); +$promise + ->then(function ($value) { + // Return a value and don't break the chain + return "Hello, " . $value; + }) + // This then is executed after the first then and receives the value + // returned from the first then. + ->then(function ($value) { + echo $value; + }); + +// Resolving the promise triggers the $onFulfilled callbacks and outputs +// "Hello, reader". +$promise->resolve('reader.'); +``` + + +## Promise forwarding + +Promises can be chained one after the other. Each then in the chain is a new +promise. The return value of a promise is what's forwarded to the next +promise in the chain. Returning a promise in a `then` callback will cause the +subsequent promises in the chain to only be fulfilled when the returned promise +has been fulfilled. The next promise in the chain will be invoked with the +resolved value of the promise. + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise(); +$nextPromise = new Promise(); + +$promise + ->then(function ($value) use ($nextPromise) { + echo $value; + return $nextPromise; + }) + ->then(function ($value) { + echo $value; + }); + +// Triggers the first callback and outputs "A" +$promise->resolve('A'); +// Triggers the second callback and outputs "B" +$nextPromise->resolve('B'); +``` + +## Promise rejection + +When a promise is rejected, the `$onRejected` callbacks are invoked with the +rejection reason. + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise(); +$promise->then(null, function ($reason) { + echo $reason; +}); + +$promise->reject('Error!'); +// Outputs "Error!" +``` + +## Rejection forwarding + +If an exception is thrown in an `$onRejected` callback, subsequent +`$onRejected` callbacks are invoked with the thrown exception as the reason. + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise(); +$promise->then(null, function ($reason) { + throw new \Exception($reason); +})->then(null, function ($reason) { + assert($reason->getMessage() === 'Error!'); +}); + +$promise->reject('Error!'); +``` + +You can also forward a rejection down the promise chain by returning a +`GuzzleHttp\Promise\RejectedPromise` in either an `$onFulfilled` or +`$onRejected` callback. + +```php +use GuzzleHttp\Promise\Promise; +use GuzzleHttp\Promise\RejectedPromise; + +$promise = new Promise(); +$promise->then(null, function ($reason) { + return new RejectedPromise($reason); +})->then(null, function ($reason) { + assert($reason === 'Error!'); +}); + +$promise->reject('Error!'); +``` + +If an exception is not thrown in a `$onRejected` callback and the callback +does not return a rejected promise, downstream `$onFulfilled` callbacks are +invoked using the value returned from the `$onRejected` callback. + +```php +use GuzzleHttp\Promise\Promise; +use GuzzleHttp\Promise\RejectedPromise; + +$promise = new Promise(); +$promise + ->then(null, function ($reason) { + return "It's ok"; + }) + ->then(function ($value) { + assert($value === "It's ok"); + }); + +$promise->reject('Error!'); +``` + +# Synchronous wait + +You can synchronously force promises to complete using a promise's `wait` +method. When creating a promise, you can provide a wait function that is used +to synchronously force a promise to complete. When a wait function is invoked +it is expected to deliver a value to the promise or reject the promise. If the +wait function does not deliver a value, then an exception is thrown. The wait +function provided to a promise constructor is invoked when the `wait` function +of the promise is called. + +```php +$promise = new Promise(function () use (&$promise) { + $promise->resolve('foo'); +}); + +// Calling wait will return the value of the promise. +echo $promise->wait(); // outputs "foo" +``` + +If an exception is encountered while invoking the wait function of a promise, +the promise is rejected with the exception and the exception is thrown. + +```php +$promise = new Promise(function () use (&$promise) { + throw new \Exception('foo'); +}); + +$promise->wait(); // throws the exception. +``` + +Calling `wait` on a promise that has been fulfilled will not trigger the wait +function. It will simply return the previously resolved value. + +```php +$promise = new Promise(function () { die('this is not called!'); }); +$promise->resolve('foo'); +echo $promise->wait(); // outputs "foo" +``` + +Calling `wait` on a promise that has been rejected will throw an exception. If +the rejection reason is an instance of `\Exception` the reason is thrown. +Otherwise, a `GuzzleHttp\Promise\RejectionException` is thrown and the reason +can be obtained by calling the `getReason` method of the exception. + +```php +$promise = new Promise(); +$promise->reject('foo'); +$promise->wait(); +``` + +> PHP Fatal error: Uncaught exception 'GuzzleHttp\Promise\RejectionException' with message 'The promise was rejected with value: foo' + + +## Unwrapping a promise + +When synchronously waiting on a promise, you are joining the state of the +promise into the current state of execution (i.e., return the value of the +promise if it was fulfilled or throw an exception if it was rejected). This is +called "unwrapping" the promise. Waiting on a promise will by default unwrap +the promise state. + +You can force a promise to resolve and *not* unwrap the state of the promise +by passing `false` to the first argument of the `wait` function: + +```php +$promise = new Promise(); +$promise->reject('foo'); +// This will not throw an exception. It simply ensures the promise has +// been resolved. +$promise->wait(false); +``` + +When unwrapping a promise, the resolved value of the promise will be waited +upon until the unwrapped value is not a promise. This means that if you resolve +promise A with a promise B and unwrap promise A, the value returned by the +wait function will be the value delivered to promise B. + +**Note**: when you do not unwrap the promise, no value is returned. + + +# Cancellation + +You can cancel a promise that has not yet been fulfilled using the `cancel()` +method of a promise. When creating a promise you can provide an optional +cancel function that when invoked cancels the action of computing a resolution +of the promise. + + +# API + + +## Promise + +When creating a promise object, you can provide an optional `$waitFn` and +`$cancelFn`. `$waitFn` is a function that is invoked with no arguments and is +expected to resolve the promise. `$cancelFn` is a function with no arguments +that is expected to cancel the computation of a promise. It is invoked when the +`cancel()` method of a promise is called. + +```php +use GuzzleHttp\Promise\Promise; + +$promise = new Promise( + function () use (&$promise) { + $promise->resolve('waited'); + }, + function () { + // do something that will cancel the promise computation (e.g., close + // a socket, cancel a database query, etc...) + } +); + +assert('waited' === $promise->wait()); +``` + +A promise has the following methods: + +- `then(callable $onFulfilled, callable $onRejected) : PromiseInterface` + + Appends fulfillment and rejection handlers to the promise, and returns a new promise resolving to the return value of the called handler. + +- `otherwise(callable $onRejected) : PromiseInterface` + + Appends a rejection handler callback to the promise, and returns a new promise resolving to the return value of the callback if it is called, or to its original fulfillment value if the promise is instead fulfilled. + +- `wait($unwrap = true) : mixed` + + Synchronously waits on the promise to complete. + + `$unwrap` controls whether or not the value of the promise is returned for a + fulfilled promise or if an exception is thrown if the promise is rejected. + This is set to `true` by default. + +- `cancel()` + + Attempts to cancel the promise if possible. The promise being cancelled and + the parent most ancestor that has not yet been resolved will also be + cancelled. Any promises waiting on the cancelled promise to resolve will also + be cancelled. + +- `getState() : string` + + Returns the state of the promise. One of `pending`, `fulfilled`, or + `rejected`. + +- `resolve($value)` + + Fulfills the promise with the given `$value`. + +- `reject($reason)` + + Rejects the promise with the given `$reason`. + + +## FulfilledPromise + +A fulfilled promise can be created to represent a promise that has been +fulfilled. + +```php +use GuzzleHttp\Promise\FulfilledPromise; + +$promise = new FulfilledPromise('value'); + +// Fulfilled callbacks are immediately invoked. +$promise->then(function ($value) { + echo $value; +}); +``` + + +## RejectedPromise + +A rejected promise can be created to represent a promise that has been +rejected. + +```php +use GuzzleHttp\Promise\RejectedPromise; + +$promise = new RejectedPromise('Error'); + +// Rejected callbacks are immediately invoked. +$promise->then(null, function ($reason) { + echo $reason; +}); +``` + + +# Promise interop + +This library works with foreign promises that have a `then` method. This means +you can use Guzzle promises with [React promises](https://github.com/reactphp/promise) +for example. When a foreign promise is returned inside of a then method +callback, promise resolution will occur recursively. + +```php +// Create a React promise +$deferred = new React\Promise\Deferred(); +$reactPromise = $deferred->promise(); + +// Create a Guzzle promise that is fulfilled with a React promise. +$guzzlePromise = new \GuzzleHttp\Promise\Promise(); +$guzzlePromise->then(function ($value) use ($reactPromise) { + // Do something something with the value... + // Return the React promise + return $reactPromise; +}); +``` + +Please note that wait and cancel chaining is no longer possible when forwarding +a foreign promise. You will need to wrap a third-party promise with a Guzzle +promise in order to utilize wait and cancel functions with foreign promises. + + +## Event Loop Integration + +In order to keep the stack size constant, Guzzle promises are resolved +asynchronously using a task queue. When waiting on promises synchronously, the +task queue will be automatically run to ensure that the blocking promise and +any forwarded promises are resolved. When using promises asynchronously in an +event loop, you will need to run the task queue on each tick of the loop. If +you do not run the task queue, then promises will not be resolved. + +You can run the task queue using the `run()` method of the global task queue +instance. + +```php +// Get the global task queue +$queue = \GuzzleHttp\Promise\queue(); +$queue->run(); +``` + +For example, you could use Guzzle promises with React using a periodic timer: + +```php +$loop = React\EventLoop\Factory::create(); +$loop->addPeriodicTimer(0, [$queue, 'run']); +``` + +*TODO*: Perhaps adding a `futureTick()` on each tick would be faster? + + +# Implementation notes + + +## Promise resolution and chaining is handled iteratively + +By shuffling pending handlers from one owner to another, promises are +resolved iteratively, allowing for "infinite" then chaining. + +```php +<?php +require 'vendor/autoload.php'; + +use GuzzleHttp\Promise\Promise; + +$parent = new Promise(); +$p = $parent; + +for ($i = 0; $i < 1000; $i++) { + $p = $p->then(function ($v) { + // The stack size remains constant (a good thing) + echo xdebug_get_stack_depth() . ', '; + return $v + 1; + }); +} + +$parent->resolve(0); +var_dump($p->wait()); // int(1000) + +``` + +When a promise is fulfilled or rejected with a non-promise value, the promise +then takes ownership of the handlers of each child promise and delivers values +down the chain without using recursion. + +When a promise is resolved with another promise, the original promise transfers +all of its pending handlers to the new promise. When the new promise is +eventually resolved, all of the pending handlers are delivered the forwarded +value. + + +## A promise is the deferred. + +Some promise libraries implement promises using a deferred object to represent +a computation and a promise object to represent the delivery of the result of +the computation. This is a nice separation of computation and delivery because +consumers of the promise cannot modify the value that will be eventually +delivered. + +One side effect of being able to implement promise resolution and chaining +iteratively is that you need to be able for one promise to reach into the state +of another promise to shuffle around ownership of handlers. In order to achieve +this without making the handlers of a promise publicly mutable, a promise is +also the deferred value, allowing promises of the same parent class to reach +into and modify the private properties of promises of the same type. While this +does allow consumers of the value to modify the resolution or rejection of the +deferred, it is a small price to pay for keeping the stack size constant. + +```php +$promise = new Promise(); +$promise->then(function ($value) { echo $value; }); +// The promise is the deferred value, so you can deliver a value to it. +$promise->resolve('foo'); +// prints "foo" +``` |