v3.0.0

A major new feature release, see release announcement.

• We'd like to emphasize that this component is production ready and battle-tested.
  We plan to support all long-term support (LTS) releases for at least 24 months,
  so you have a rock-solid foundation to build on top of.

• The v3 release will be the way forward for this package. However, we will still
  actively support v2 and v1 to provide a smooth upgrade path for those not yet
  on the latest versions.

This update involves some major new features and a minor BC break over the
v2.0.0 release. We've tried hard to avoid BC breaks where possible and
minimize impact otherwise. We expect that most consumers of this package will be
affected by BC breaks, but updating should take no longer than a few minutes.
See below for more details:

• BC break: PHP 8.1+ recommended, PHP 7.1+ required.
  (#138 and #149 by @WyriHaximus)

• Feature / BC break: The PromiseInterface now includes the functionality of the old ExtendedPromiseInterface and CancellablePromiseInterface.
  Each promise now always includes the then(), catch(), finally() and cancel() methods.
  The new catch() and finally() methods replace the deprecated otherwise() and always() methods which continue to exist for BC reasons.
  The old ExtendedPromiseInterface and CancellablePromiseInterface are no longer needed and have been removed as a consequence.
  (#75 by @jsor and #208 by @clue and @WyriHaximus)

  // old (multiple interfaces may or may not be implemented)
  assert($promise instanceof PromiseInterface);
  assert(method_exists($promise, 'then'));
  if ($promise instanceof ExtendedPromiseInterface) { assert(method_exists($promise, 'otherwise')); }
  if ($promise instanceof ExtendedPromiseInterface) { assert(method_exists($promise, 'always')); }
  if ($promise instanceof CancellablePromiseInterface) { assert(method_exists($promise, 'cancel')); }
  
  // new (single PromiseInterface with all methods)
  assert($promise instanceof PromiseInterface);
  assert(method_exists($promise, 'then'));
  assert(method_exists($promise, 'catch'));
  assert(method_exists($promise, 'finally'));
  assert(method_exists($promise, 'cancel'));

• Feature / BC break: Improve type safety of promises. Require mixed fulfillment value argument and Throwable (or Exception) as rejection reason.
  Add PHPStan template types to ensure strict types for resolve(T $value): PromiseInterface<T> and reject(Throwable $reason): PromiseInterface<never>.
  It is no longer possible to resolve a promise without a value (use null instead) or reject a promise without a reason (use Throwable instead).
  (#93, #141 and #142 by @jsor, #138, #149 and #247 by @WyriHaximus and #213 and #246 by @clue)

  // old (arguments used to be optional)
  $promise = resolve();
  $promise = reject();
  
  // new (already supported before)
  $promise = resolve(null);
  $promise = reject(new RuntimeException());

• Feature / BC break: Report all unhandled rejections by default and remove done() method.
  Add new set_rejection_handler() function to set the global rejection handler for unhandled promise rejections.
  (#248, #249 and #224 by @clue)

  // Unhandled promise rejection with RuntimeException: Unhandled in example.php:2
  reject(new RuntimeException('Unhandled'));

• BC break: Remove all deprecated APIs and reduce API surface.
  Remove some(), map(), reduce() functions, use any() and all() functions instead.
  Remove internal FulfilledPromise and RejectedPromise classes, use resolve() and reject() functions instead.
  Remove legacy promise progress API (deprecated third argument to then() method) and deprecated LazyPromise class.
  (#32 and #98 by @jsor and #164, #219 and #220 by @clue)

• BC break: Make all classes final to encourage composition over inheritance.
  (#80 by @jsor)

• Feature / BC break: Require array (or iterable) type for all() + race() + any() functions and bring in line with ES6 specification.
  These functions now require a single argument with a variable number of promises or values as input.
  (#225 by @clue and #35 by @jsor)

• Fix / BC break: Fix race() to return a forever pending promise when called with an empty array (or iterable) and bring in line with ES6 specification.
  (#83 by @jsor and #225 by @clue)

• Minor performance improvements by initializing Deferred in the constructor and avoiding call_user_func() calls.
  (#151 by @WyriHaximus and #171 by @Kubo2)

• Minor documentation improvements.
  (#110 by @seregazhuk, #132 by @CharlotteDunois, #145 by @danielecr, #178 by @WyriHaximus, #189 by @SrDante, #212 by @clue, #214, #239 and #243 by @SimonFrings and #231 by @nhedger)

The following changes had to be ported to this release due to our branching
strategy, but also appeared in the 2.x branch:

• Feature: Support union types and address deprecation of ReflectionType::getClass() (PHP 8+).
  (#197 by @cdosoftei and @SimonFrings)

• Feature: Support intersection types (PHP 8.1+).
  (#209 by @bzikarsky)

• Feature: Support DNF types (PHP 8.2+).
  (#236 by @nhedger)

• Feature: Port all memory improvements from 2.x to 3.x.
  (#150 by @clue and @WyriHaximus)

• Fix: Fix checking whether cancellable promise is an object and avoid possible warning.
  (#161 by @smscr)

• Improve performance by prefixing all global functions calls with \ to skip the look up and resolve process and go straight to the global function.
  (#134 by @WyriHaximus)

• Improve test suite, update PHPUnit and PHP versions and add .gitattributes to exclude dev files from exports.
  (#107 by @carusogabriel, #148 and #234 by @WyriHaximus, #153 by @reedy, #162, #230 and #240 by @clue, #173, #177, #185 and #199 by @SimonFrings, #193 by @woodongwong and #210 by @bzikarsky)

The following changes were originally planned for this release but later reverted
and are not part of the final release:

• Add iterative callback queue handler to avoid recursion (later removed to improve Fiber support).
  (#28, #82 and #86 by @jsor, #158 by @WyriHaximus and #229 and #238 by @clue)

• Trigger an E_USER_ERROR instead of throwing an exception from done() (later removed entire done() method to globally report unhandled rejections).
  (#97 by @jsor and #224 and #248 by @clue)

• Add type declarations for some() (later removed entire some() function).
  (#172 by @WyriHaximus and #219 by @clue)